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Chromatographic Separation of Polymers
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Chromatographic Separation of Polymers

  • Taihyun Chang*
    Taihyun Chang
    Department of Chemistry and Division of Advanced Materials Science, Pohang University of Science and Technology, Pohang, 37673, Korea
    *E-mail: [email protected]
    More by Taihyun Chang
DOI: 10.1021/bk-2018-1281.ch001
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Publication Date (Web):October 29, 2018
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Copyright © 2018 American Chemical Society. This publication is available under these Terms of Use.
Recent Progress in Separation of Macromolecules and Particulates
Chapter 1pp 1-17
ACS Symposium SeriesVol. 1281
ISBN13: 9780841233096eISBN: 9780841233089

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Abstract

Polymers are usually mixtures of molecules that are inhomogeneous in various molecular characteristics. For precise characterization of polymers, distributions in all of these molecular characteristics need to be addressed, which is generally an impossible task. However, it is often sufficient in practice to analyze a limited number of molecular characteristics. Liquid chromatography is the most widely used tool for this purpose and has made remarkable progress during the last half century in both instrumentation and understanding of the separation mechanism. In this chapter, various chromatographic techniques developed for polymer separation are briefly reviewed.

This publication is licensed for personal use by The American Chemical Society.

1 Introduction

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Except for some biopolymers, most synthetic and natural polymers are not homogeneous in various molecular characteristics such as molecular weight (MW), chemical composition, chain architecture, etc. Distributions in the molecular characteristics are reflected in the final properties of polymeric materials and the precise characterization of these distributions is important in design and performance control of the polymeric materials. To analyze the multivariate distributions of a polymer sample, it is desirable to separate the polymer sample first according to the molecular characteristics of interest. For this purpose, liquid chromatography (LC) is the most commonly used technique.
Among numerous variations of the LC methods, size exclusion chromatography (SEC) has been used most widely for molecular weight distribution (MWD) analysis of polymers ( 1, 2, 3, 4). SEC separates polymer analytes using the distribution equilibrium of polymer chains between a common solvent in the pore and the interstitial volumes of the LC column packed with porous spherical particles. In an ideal SEC separation, the column packing materials should not adsorb the polymers and the distribution equilibrium of the polymers is solely due to the entropic exclusion of polymer chains from the pores ( 5). Therefore, the SEC eluent is commonly a strong (promoting desorption) solvent for the polymer analytes. (The solvent strength is a different concept from the thermodynamic solvent quality but a strong solvent is generally a good solvent.) SEC separation has advantages over other classical fractionation methods in speed and the amount of the sample required. SEC separation can be combined with a variety of detectors such as light scattering and viscosity detectors that allow measuring absolute MW and intrinsic viscosity online in conjunction with concentration detectors such as UV absorption or differential refractive index detectors.
Nonetheless, it is important to keep its limitation in mind. First, SEC separates the polymers according to their hydrodynamic size. While the separation being sensitive to one molecular characteristic is of course a distinct merit, as it is the principle of the universal calibration in SEC ( 6), SEC separation cannot distinguish between other molecular characteristics such as chain architecture or chemical composition beyond the chain size in the eluting solvent. Secondly, the resolution of SEC is limited due to the band broadening of the separation method. Although band broadening is a general phenomenon in chromatography, it needs to be considered carefully in the MWD characterization of polymers since the elution peak of a polymer sample is a convolution product of MWD and the instrumental band broadening ( 7).
To complement the limitation of SEC, another LC method utilizing the enthalpic interaction of analytes with the stationary phase, called liquid adsorption chromatography or interaction chromatography, has been increasingly used in recent years ( 8, 9, 10, 11, 12, 13). In principle, it is nothing but a typical HPLC method widely used for the separation of small molecules and the term of interaction chromatography (IC) will be used in contrast to SEC in this chapter. Since the IC separation is based on the interaction of polymer analytes with the stationary phase (surface of the packing materials in the column), the distribution equilibrium of the analytes between the mobile and the stationary phases is sensitive to not only MW but also the chemical nature of the polymers. The eluents used for IC separations are generally weak (promoting adsorption) to induce appropriate interaction strength. In terms of instrumentation, SEC and IC are essentially the same LC methods except for the choice of the stationary (column) and mobile (eluent) phase. IC and SEC separation modes can even be interconverted at the same stationary phase by changing either the eluent (composition if a mixed solvent is used) or column temperature. (Figure 1) shows the effect of solvent composition and column temperature on the SEC/IC retention of polystyrene samples with narrow MWD.

Figure 1

Figure 1. Chromatograms of six polystyrene standards (Mw: (1) 2.5k, (2) 12k, (3) 29k, (4) 165k, (5) 502k, (6) 1,800k). Single column (Nucleosil C18; 250 x 4.6 mm, 5 μm particle, 100 Å pore) was used and the flow rate was 0.5 mL/min. (Left) Solvent composition effect at a fixed column temperature of 30.5°C with the mixed eluents of CH2Cl2/CH3CN at different compositions as labeled in the plot. (Right) Temperature effect at a fixed eluent composition of 57/43 (v/v). The isothermal chromatograms were obtained at different column temperatures as labeled in the plot. The CAP condition is established at the composition of CH2Cl2/CH3CN = 57/43 (v/v) and the column temperature of 30.5°C. The vertical dashed lines indicate the elution time of the injection solvent peak.
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From reference ( 14). This figure was reproduced with permission of Wiley and Sons.
In the LC separation of polymers, there exists an interesting transition behavior from the SEC mode to the IC mode, which is called the critical adsorption point (CAP) ( 15). This behavior is the result of compensation of the exclusion and the interaction effects of polymer chains with the porous stationary phase. At this point, polymer chains undergo a ‘phase transition’ from the unadsorbed state to the adsorbed state ( 16). The LC method utilizing this phenomenon is called as liquid chromatography at the critical condition (LCCC). In this chapter, various LC methods used in the separation of polymers will be briefly introduced. Since SEC is a well-established method, it will not be treated further.

2 Interaction Chromatography

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The IC separation of polymers began in the late 1960’s using thin layer chromatography ( 17, 18). They demonstrated the successful separation of copolymers according to composition and the separation of homopolymers according to MW. Also the transition behavior between SEC and IC was observed by changing the solvent composition ( 19). Higher resolution IC separation using column LC followed later ( 20, 21). IC separation utilizes the interaction of polymeric solutes with the stationary phase and it is able to separate polymers according to their chemical composition distribution (CCD) and functionality as well as MWD. Also the band broadening in IC was found much smaller than SEC ( 22, 23). ((Figure 2))

Figure 2

Figure 2. Temperature Gradient Interaction Chromatography (TGIC) separation of 14 standard polystyrenes showing the high resolution separation of IC. The column temperature program is shown in the plot. Mobile phase was a mixture of CH2Cl2/CH3CN (57/43, v/v). Single C18 bonded silica column (Nucleosil C18, 250 x 2.1 mm, 5 μm, 100 Å) was used and the flow rate was 0.1 mL/min. TGIC shows much lower Mw/Mn values than SEC indicating higher resolution of IC than SEC.
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From reference ( 24). This figure was reproduced with permission from American Laboratory.
The sensitivity of IC to multiple molecular characteristics is a merit over SEC, however, it often makes the result of the IC separation more complicated since the retention of polymers is controlled by multiple factors. Furthermore, the IC retention of a polymer sample can vary a lot for the polymers with wide distribution in the molecular characteristics. For an example, the interaction energy of a homopolymer solute is expected to be proportional to MW ( 25) and the retention of a polymer solute (proportional to the distribution equilibrium constant) increases exponentially with its MW. Therefore, an isocratic (constant eluent composition) and isothermal IC elution of a polymer sample having a wide MWD is practically impossible. To overcome this problem, the interaction strength is controlled during the elution by changing either the solvent composition (solvent gradient elution) or column temperature (temperature gradient elution) as demonstrated in (Figure 1).
In the solvent gradient interaction chromatography, solvent composition is changed from a weak to strong eluent condition so that the polymers elute in order of increasing interaction strength. This method is also called gradient polymer elution chromatography. Statistical copolymers of high MW elute near the CAP condition of corresponding chemical composition independent of MW and the solvent gradient IC is a powerful tool to separate random copolymers or polymer mixtures according to their chemical composition ( 26, 27, 28, 29, 30).
In temperature gradient interaction chromatography (TGIC), the eluent composition is fixed near the CAP condition, and the column temperature is programed to change the separation mode from IC to SEC ( 31, 32). The column temperature is usually raised to promote desorption during the separation under the presumption that the adsorption of polymer is an exothermic process and the solvent strength increases with the temperature raise. But an inverse temperature dependence is also observed in a few polymer-eluent-column systems. For a successful TGIC separation of the polymers showing the inverse temperature dependency, the column temperature needs to be decreased during the elution to increase the solvent strength. A representative example is the separation of polyethylene oxide-aqueous organic solvents-C18 bonded silica columns ( 33). The inverse temperature dependence (retention increases as the column temperature increases) indicates that the adsorption process is endothermic, i.e. energetically unfavorable. Similar inverse temperature dependency was also observed in polystyrene-chloroform/n-hexane-bare silica column ( 34) and poly(methyl methacrylate)-1,4 dioxane/CH2Cl2-bare silica column ( 35). It shows that the adsorption of polymer chains to the stationary phase is not a simple enthalpic interaction between the polymer chains with the surface of the porous medium. Hydrophobic interaction was proposed to explain the inverse temperature dependence of polyethylene oxide with C18 bonded silica stationary phase ( 36).
While solvent gradient elution is a common HPLC technique to separate the samples of wide MWD and/or CCD, the composition change of the mobile phase limits the utility of the detectors sensitive to the composition change (e.g. refractive index, light scattering, and viscosity detectors) due to the large background signal drift. On the other hand, temperature gradient elution is an isocratic elution method that allows more freedom in choosing detectors with appropriate temperature control. However, the temperature change cannot vary the solvent strength of the eluent as much as the solvent composition variation, and TGIC is suitable for the analysis of polymer systems that need a fine control instead of a large change of the solvent strength. TGIC has been successfully applied for high resolution separation of homopolymers according to MW ((Figure 2)) ( 22, 23), separation according to chemical composition ( 37), separation of polymer mixtures ((Figure 3)) ( 38, 39), fractionation of individual blocks in block copolymers ( 40, 41), separation of branched polymers ( 42, 43), separation according to the stereoregularity ( 44), and separation according to the isotopic content ( 45, 46).

Figure 3

Figure 3. TGIC separation of a mixture of 10 polystyrene (a-k: 1.7k, 5.1k, 11.6k, 22.0k, 37.3k, 68.0k, 114k, 208k, 502k, 1090k, 2890k) and 5 poly(methyl methacrylate) (1-5: 1500k, 501k, 77.5k, 8.5k, 2.0k) standards. S is the injection solvent peak. The temperature program is also shown in the plot. Three columns (Nucleosil C18, 250 x 4.5 mm, 100Ǻ & 500 Ǻ & 1,000Ǻ) are used and the mobile phase is a mixture of CH2Cl2/CH3CN(54/46 (v/v)).
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From reference ( 38).
There are other LC techniques related to IC. One is the barrier method in which the separation mode is SEC and a narrow weak solvent plug (barrier) is injected prior to the sample injection ( 47, 48, 49). Since the polymer analytes are under SEC condition, they move faster than the barrier and catch up to the barrier in the separation column. Depending on the solvent strength of the barrier to the polymer species, some polymer species (for which the solvent strength of the plug is above the adsorption threshold) can pass the barrier while some cannot. The polymer species that cannot pass the barrier elute later with the barrier solvent plug. This method can be used effectively to separate polymer mixtures and multiple barriers of different solvent strength can be used to separate mixtures of more than two components ( 50). An evolution of the barrier method is the SEC-gradient elution. In this technique, instead of abrupt weak solvent plugs, a gradient of solvent strength (from strong to weak) is produced in the SEC column prior to the sample injection. The polymer species moves faster until it reaches the solvent composition of the adsorption threshold and then it moves together with the solvent. Polymer species can be separated depending on their adsorption threshold solvent composition ( 51, 52).

3 Critical Adsorption Point and Liquid Chromatography at Critical Condition

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Critical adsorption point (CAP) is an interesting phenomenon playing an important role in the LC separation of polymers. At the CAP, the steric repulsion of the polymer segments from a solid surface is compensated by the attractive interaction with the surface. When a porous medium is used in the LC separation of polymers, the size exclusion effect of the polymers from the pores is balanced by the attractive interaction of the polymers with the surface of the packing materials ( 15, 53, 54), and the distribution of the polymer chains in the pores and at the interstitial space becomes the same at the CAP. The CAP condition is usually found at a separation condition (solvent composition and temperature) between the SEC mode and the IC mode elution as shown in (Figure 1). A collection of the critical conditions for various polymers was reported ( 55).

Figure 4

Figure 4. LCCC chromatograms of cyclic PSs and corresponding linear precursors at the CAP of linear PS. Linear precursors elute at about the same retention time (5.4 min) independent of the MW while the retention of cyclic polymer increases with molecular weight. The small peaks appearing near tR = 5 min are the injection solvent peaks. The elution peak of cyclic polymers is completely separated from the linear precursors down to the baseline. The chromatograms of cyclic PS (black line) show that most of the samples contain contaminants, mostly the linear precursors.
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From reference ( 77).
A distinct feature observed at the CAP of a polymer species is the suppression of MW dependence in the LC retention, as the polymer elutes near the injection solvent peak independent of MW. This effect is sometimes called‘chromatographic invisibility’ and the ‘transparency’ of the polymer chain helps monitor the other molecular characteristics free from the MWD of the polymer under the critical condition. The LC technique utilizing this phenomenon is called LCCC and LCCC has been successfully employed for the separation and characterization of complex polymer systems such as the separation of individual components in polymer mixtures ( 56, 57, 58), the characterization of the individual blocks in block copolymers ( 59, 60, 61, 62, 63), and the separation of polymers according to the functionality ( 64, 65, 66, 67, 68, 69, 70, 71).
Another merit of LCCC is the ability to separate polymers by chain architecture. It was found that the polymers of different architecture show CAP at different temperatures ( 72, 73). This means that at the CAP of a linear polymer, branched polymers or cyclic polymers are retained differently and could be resolved from linear polymers. For a good example, LCCC can separate cyclic polymers from their linear precursors better than SEC or IC((Figure 4)). It was theoretically predicted ( 15, 74) and experimentally demonstrated that LCCC separation is the best available method for the purification of cyclic polymers from linear polymer byproducts present in samples synthesized by a ring-closure reaction of telechelic precursors ( 75, 76, 77, 78, 79). It was found that very small contamination of the linear chains changes the melt viscoelasticity of cyclic polymers dramatically ( 80). It was also found that the difference in the chain ends (the presence of different chemical groups) generated a small but noticeable effect on the CAP condition in addition to the effect of the chain architecture ( 72).

4 Two-Dimensional Liquid Chromatography (2D-LC)

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In multidimensional chromatography, more than one chromatography methods are combined to separate the analytes. In practice, two-dimensional analysis using two different LC methods (2D-LC) is most widely used ( 81, 82, 83, 84, 85). Cross developments in thin layer chromatography is a good example of 2D-LC ( 18). In a comprehensive 2D-LC of a column chromatography, the effluent of the first dimension (1st-D) LC is injected to the second dimension (2nd-D) LC separation without loss. The chromatogram of a comprehensive 2D-LC is an overlay of the 2nd-D LC chromatograms. Therefore, repetitive 2nd-D LC separations need to be done rapidly to synchronize with the flow rate of the 1st-D LC separation and to reduce the total analysis time. Nonetheless, shortening the analysis time (achievable by high flow rate and/or by using a shorter column) may deteriorate the resolution and the analysis time and the resolution needs to be compromised for an optimum result.
Another important consideration for a successful 2D-LC separation is the solvent compatibility between the two LC separations. Since two different LC methods are combined, the injection solvent (1st-D LC solvent) is usually different from the eluent in the 2nd-D LC; poor transfer of the polymer species from the injection solvent to the eluent can deteriorate the 2nd-D LC separation. The most frequently observed problem is a break-through phenomenon in which the polymer species elute in the injection solvent plug without further separation in the 2nd-D LC ( 86). This problem occurs often when the 2nd-D LC eluent is weaker than the injection solvent (the eluent of the 1st-D LC). The compatibility problem is far less serious if the 2nd-D LC eluent is a stronger solvent for the polymer species.

Figure 5

Figure 5. 2D-LC chromatograms recorded by a UV absorption detector (260 nm) showing polymer MW (SEC) vs. 1st-D LC retention time at different column temperatures; SEC (T = 63.0 °C), LCCC (T = 37.2 °C), IC (T = 28.0 °C). PS standards: 3.3k, 10k, 31k, 113k, 384k, 1800k. 1st-D IC (abscissa): Nucleosil C18 150 x 4.6 mm, 7 μm, 500 Å); Eluent: CH2Cl2/CH3CN = 57/43 (v/v); Flow rate: 0.05 mL/min. 2nd-D SEC (ordinate): PL PolyPore (250 × 4.6 mm); Eluent: THF; Flow rate: 1.7 mL/min; Column temperature: 110 °C.
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From the reference ( 92). This figure was reproduced with permission from Elsevier.
The most common configuration of 2D-LC for polymer analysis is a combination of IC and SEC (IC x SEC): IC is used as the 1st-D LC to separate the polymers in terms of molecular characteristics sensitive to the IC separation and SEC is used for the 2nd-D LC for a further separation according to the chain size. SEC is suitable for a 2nd-D LC separation since the SEC eluent is a strong solvent and the solvent compatibility problem is not serious. In addition, by virtue of being an isocratic/isothermal elution, SEC separation can be repeated rapidly and multiple detection is possible. Furthermore, the SEC elution volume is always smaller than the total void volume of a column (total permeation limit for the column set), which is good for rapid/repetitive runs of the 2nd-D LC separation. Size dependent SEC separation is often affected by molecular characteristics other than MW, but once homogeneity of the sample is improved after the 1st-D separation, SEC separation can be better correlated with MW ( 43, 87). Furthermore, with recent developments, a reasonable SEC separation can be completed in a few minutes ( 88, 89, 90, 91). (Figure 5) shows 2D-LC (IC x SEC) contour plots of PS standards demonstrating the three different chromatographic elution modes ( 92).

Figure 6

Figure 6. NP-TGIC × RPLC 2D-LC chromatogram of a low MW polystyrene-block-polyisoprene (1.7k-0.7k, Mw/Mn: 1.06) (1st-D NP-TGIC: Nucleosil Diol, 250 x 7.8 mm, 7 μm, 100 Å, Eluent: isooctane/THF=97/3 (v/v); Flow rate: 0.05 mL/min. 2nd-D RPLC: Kromasil C18, 150 x 4.6 mm, 5 μm, 100 Å, Eluent: CH2Cl2/CH3CN=53/47 (v/v), Flow rate: 1.1 mL/min, Trap column: Alltech C18, 3 μm, 100 Å, 33 × 70 mm).
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From reference ( 93).
Although the use of other LC methods as a 2nd-D LC is not as popular as SEC, IC x IC and IC x LCCC have been used for more efficient characterizations of complex polymers than IC x SEC. (Figure 6) shows the IC x IC 2D-LC separation of a low MW block copolymer in which a full resolution of invidual oligomers is achieved. IC as a 2nd-D LC is relatively rare since IC separation is usually not operated in an isocratic/isothermal elution mode, making it difficult for rapid/repetitive runs. Furthermore, IC eluents are usually weak solvents and the solvent compatibility problem is more serious. Therefore, extra measures are often needed to connect two ICs without solvent compatibility problems ( 46, 93). On the other hand, LCCC can be used more easily as a 2nd-D LC since it is operated in isocratic/isothermal elution mode. If the 1st-D IC elution is done near the CAP condition, as in most TGIC separations, the solvent compatibility problem is not serious since the 1st-D IC and the 2nd-D LCCC uses a common solvent ( 69, 94)-96.

5 Epilogue

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In this brief review, the discussion is restricted toseparation with respect to the molecular characteristics of polymers, however, identification of the polymer species after the separation is important as well. Multiple detection provides with much more information for a given separation. Various methods have been developed for the detection of the HPLC effluent beyond the common concentration detectors such as UV, RI and evaporative light scattering detectors. Light scattering and viscosity detectors are no longer new detection methods but their use is still largely limited to SEC. Other useful spectroscopic methods for structural identification are infrared and nuclear magnetic resonance spectroscopic detections.97-98 Mass spectrometry has made rapid progress in polymer analysis in recent years due to the development of soft ionization methods.99-100 It is a powerful tool to do both separation with respect to mass and structural identification of polymers but is still limited to relatively low MW range, and various discriminations in the ionization process need to be improved to be a general tool for polymer characterization. Current use of mass spectrometry is more or less limited to the identification of narrowly dispersed fractions obtained by an adequate separation method.
Although LC separation methods are widely used for the polymer characterization at the moment, other separation methods such as hydrodynamic chromatography101 and field flow fractionation102-103 have their own merits where the LC methods do not work satisfactorily, e.g. very high molecular weight polymers, strongly adsorbing polymers, nanoparticles, etc. Polymers are complex mixtures and a precise characterization of the multivariate distributions is an extremely difficult, if not impossible, task. In many cases, however, the information in need can be obtained by judiciously selecting right separation and detection methods.

References

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    This review presents recent developments in the anal. of various heterogeneities in synthetic polymers by a variety of liq. chromatog. sepn. as well as detection methods. Synthetic polymers are rarely homogeneous chem. species but have multivariate distributions in mol. wt., chem. compn., chain architecture, functionality, and so on. For a precise characterization of synthetic polymers, all the distributions need to be detd., which is a difficult task, if not impossible. Fortunately in most of the cases it is sufficient to analyze a limited no. of mol. characteristics in order to obtain the information required for a given purpose. Nonetheless, it is still nontrivial if there exists distributions for more than one mol. characteristic. There have been continuing efforts to solve the problem. One approach is to find chromatog. methods sensitive to one mol. characteristic only. In favorable cases, the effect of all but one mol. characteristic can be suppressed to a negligible level. Various interaction chromatog. techniques as well as size exclusion chromatog. are employed for the purpose. Also the multiple detection methods each sensitive to a specific mol. characteristic can provide addnl. information. Various detection methods developed recently such as FT-IR, FT-NMR, and mass spectrometry brought about significant progress in the characterization of complex polymers. This review presents the recent developments in the anal. of various heterogeneities in synthetic polymers by a variety of liq. chromatog. sepn. as well as detection methods.
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    Uliyanchenko E. van der Wal S. Schoenmakers P. J. Challenges in polymer analysis by liquid chromatography Polym. Chem. 2012 3 2313 2335
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    Challenges in polymer analysis by liquid chromatography
    Uliyanchenko, Elena; van der Wal, Sjoerd; Schoenmakers, Peter J.
    Polymer Chemistry (2012), 3 (9), 2313-2335CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
    A review. Synthetic polymers are very important in our daily life. Liq. chromatog. (LC) techniques are very commonly used for mol. characterization of polymers. LC anal. of macromols. is more challenging than anal. of low-mol.-wt. compds. The present review focuses on difficulties assocd. with LC anal. of synthetic polymers. The approaches that allow bringing poorly sol. polymers within the scope of LC are discussed. Different LC modes used for polymer sepns. are reviewed and assocd. practical challenges are identified. Aspects of optimization of sepns. in terms of resoln. (retention factors, selectivity and efficiency) and anal. time are discussed. Modern technologies that may pos. affect the trade-off between speed of anal. and efficiency are considered in this respect. Finally, the issue of detection in LC of polymers is addressed. The advantages and limitations of different detection techniques as well as hyphenated techniques are discussed.
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    Radke W. Polymer separations by liquid interaction chromatography: Principles - prospects - limitations J. Chromatogr. A 2014 1335 62 79
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    Polymer separations by liquid interaction chromatography: Principles - prospects - limitations
    Radke, Wolfgang
    Journal of Chromatography A (2014), 1335 (), 62-79CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
    A review. Most heterogeneities of polymers with respect to different structural features cannot be resolved by only size exclusion chromatog. (SEC), the most frequently applied mode of polymer chromatog. Instead, methods of interaction chromatog. became increasingly important. However, despite the increasing applications the principles and potential of polymer interaction chromatog. are still often unknown to a large no. of polymer scientists. The present review will explain the principles of the different modes of polymer chromatog. Based on selected examples it is shown which sepn. techniques can be successfully applied for sepns. with respect to the different structural features of polymers.
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    Chang T. Lee H. C. Lee W. Park S. Ko C. H. Polymer characterization by temperature gradient interaction chromatography Macromol. Chem. Phys. 1999 200 2188 2204
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    Polymer characterization by temperature gradient interaction chromatography
    Chang, Taihyun; Lee, Hee Cheong; Lee, Wonmok; Park, Soojin; Ko, Changhee
    Macromolecular Chemistry and Physics (1999), 200 (10), 2188-2204CODEN: MCHPES; ISSN:1022-1352. (Wiley-VCH Verlag GmbH)
    A review with 45 refs. on the authors' recent results. Thermodn. principles and some applications of the temp. gradient interaction chromatog. (TGIC) recently developed for the characterization of synthetic polymers are described. TGIC is a form of high performance liq. chromatog. (HPLC) that varies column temp. in a programmed manner to control the retention of polymeric species during isocratic elution. The retention of polymers strongly depends on their mol. wts., and the polymers are well sepd. by TGIC in terms of their mol. wts. TGIC is superior to size exclusion chromatog. (SEC) in resoln. and sample loading capacity, and has higher sensitivity to mol. wt. in the anal. of nonlinear polymers. TGIC has an advantage over solvent gradient HPLC because it permits the use of refractive index-sensitive detection method such as differential refractometry and light scattering due to the isocratic elution. In addn., temp. provides finer and more reproducible retention control than the solvent compn., which is important in detg. the mol. wt. distribution by secondary calibration methods. With TGIC anal., the authors found that the mol. wt. distribution of anionically polymd. polymers is much narrower than was generally accepted from SEC anal. The authors also found the TGIC sepn. conditions for polystyrene, polyisoprene, poly(Me methacrylate), poly(vinyl chloride), and poly(vinyl acetate) over wide mol. wt. range. Because of its sensitivity to the mol. wt. alone, TGIC was successfully applied to the characterization of star-shaped polystyrene, and the detailed linking kinetics between living polystyrene anions and a chlorosilane linking agent was investigated.
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    Gorbunov A. A. Skvortsov A. M. Statistical properties of confined macromolecules Adv. Colloid Interface Sci. 1995 62 31 108
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    Statistical properties of confined macromolecules
    Gorbunov, Alexei A.; Skvortsov, Alexander M.
    Advances in Colloid and Interface Science (1995), 62 (1), 31-108CODEN: ACISB9; ISSN:0001-8686. (Elsevier)
    A review, with 120 refs. The review presents in a consistent manner the results of a rigorous theory which describes the equil. behavior of an isolated macromol. in a porous medium. An exactly solvable model of a macromol. in a slit-like pore is used as the base model. Various behavioral regimes are analyzed for a macromol. in a pore, realizable at various mol.-to-pore size ratios, as also with varied adsorption interactions. The effect of polymer chain rigidity is discussed, and so is the specific behavior of a macromol. in different forms of pores. Presented also are the results of a rigorous theory for ideal cyclic macromols. in pores under conditions of varied adsorption interactions.Theory is compared with exptl. results on the partition coeffs. of macromols. at no adsorption and with adsorption interactions taking place. Comparing theory with expt. enables detn. of a correlation length of adsorption for various polymer-solvent-adsorbent systems.The basic results are discussed in terms of the sealing theories which account for the excluded vol. effects and for the effect of the thermodn. quality of the solvent upon the behavior of linear and cyclic macromols. in pores.Alongside the discussion on the properties of individual confined macromols., another situation is analyzed: that where a molten amorphous polymer is in contact with solid particles. Various approaches are examd. toward describing such systems. It is suggested and justified that the conformations of flexible-chain macromols. in an amorphous polymer amidst filler particles are identical to the conformations of an isolated chain at the crit. adsorption interaction energy.
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    Inagaki H. Matsuda H. Kamiyama F. Determination of compositional heterogeneity in copolymers by thin-layer chromatography. I. Preliminary results for styrene-acrylate copolymers Macromolecules 1968 1 520 5
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    Determination of compositional heterogeneity in copolymers by thin-layer chromatography. I. Preliminary results for styrene-acrylate copolymers
    Inagaki, Hiroshi; Matsuda, Hisayuki; Kamiyama, Fumio
    Macromolecules (1968), 1 (6), 520-5CODEN: MAMOBX; ISSN:0024-9297.
    The feasibility of detg. the compositional heterogeneity of copolymers by thin-layer chromatog. was demonstrated. Homopolymers and copolymers of styrene and Me acrylate prepd. at various monomer feed ratios were used as test samples. Seven solvents, chosen appropriately from the eluotropic series, were used to develop the chromatograms. No intermediate Rf value was observed, since some species remained immobile while others reached the solvent front. Similar unfavorable results were observed using solvent mixts. Good sepn. was achieved by developing in a concn. gradient, using the system CCl4-MeOAc. By this procedure, the compn. distribution curve of a high-conversion styrene-Me acrylate copolymer was detd. The results agreed well with a calcd. curve based on radical copolymn. kinetics. The limitations of the new technique are discussed briefly. Finally, preliminary data are presented indicating that, under suitable conditions, sepn. of copolymers with respect to differences in steric monomer arrangement is also possible.
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    Belenkii B. G. Gankina E. S. Thin-Layer Chromatography of Polymers Introductory Lecture J. Chromatogr. 1970 53 3 25
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    Belenkii B. G. Gankina E. S. Tennikov M. B. Vilenchik L. Z. Fundamental Aspects of Adsorption Chromatography of Polymers and their Experimental Verification by Thin-Layer Chromatography J. Chromatogr. 1978 147 99 110
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    Fundamental aspects of adsorption chromatography of polymers and their experimental verification by thin-layer chromatography
    Belen'kii, B. G.; Gankina, E. S.; Tennikov, M. B.; Vilenchik, L. Z.
    Journal of Chromatography (1978), 147 (), 99-110CODEN: JOCRAM; ISSN:0021-9673.
    Math. equations are derived to provide a basis for interpretation of the mechanism of the adsorption chromatog. of polymers; the equations describe the peculiarities of both adsorption chromatog. and mol.-sieve chromatog. The equations were verified exptl. by use of various polystyrene [9003-53-6] samples.
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    Teramachi S. Hasegawa A. Shima Y. Akatsuka M. Nakajima M. Separation of Styrene-Methyl Acrylate Copolymer According to Chemical Composition, Using High-Speed Liquid Chromatography Macromolecules 1979 12 992
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    Separation of styrene-methyl acrylate copolymer according to chemical composition, using high-speed liquid chromatography
    Teramachi, Shinya; Hasegawa, Akira; Shima, Yukio; Akatsuka, Makoto; Nakajima, Masahiko
    Macromolecules (1979), 12 (5), 992-6CODEN: MAMOBX; ISSN:0024-9297.
    High-speed liq. chromatog. of a mixt. of Me acrylate-styrene copolymers [25036-19-5] having sharp chem. compn. distributions and different chem. compns. on silica gel columns with micropore size <50 Å by gradient elution with CCl4-MeOAc gave chromatograms having discrete peaks corresponding to the original components. The apparent chem. compn. distribution of components was detd. from the chromatogram by using the resp. components as internal stds., and compared with that calcd. from copolymn. kinetics. The distribution obtained on a high-efficiency column was in fairly good agreement with the theor. distribution. The mol. sieve effect in the columns used was negligible.
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    Armstrong D. W. Bui K. H. Nonaqueous Reversed-Phase Liquid Chromatographic Fractionation of Polystyrene Anal. Chem. 1982 54 706 708
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    Nonaqueous reversed-phase liquid chromatographic fractionation of polystyrene
    Armstrong, Daniel W.; Bui, K. H.
    Analytical Chemistry (1982), 54 (4), 706-8CODEN: ANCHAM; ISSN:0003-2700.
    A binary solvent mobile phase (i.e., CH2Cl2 and MeOH) in conjunction with reversed-phase thin-layer chromatog. (TLC) or high-performance liq. chromatog. (HPLC) can be used to fractionate polystyrene [9003-53-6]. Sepn. times are ∼15 min and the resoln. is better than comparable mol. sieve or TLC methods. Sepn. of polymers with mol. wts. ≤107 posed no problems for this technique. The TLC fractionation of polystyrene occurs as a result of the change in mobile phase compn. along the length of the chromatogram. This is verified by gradient reversed-phase HPLC expts. and by direct anal. of the mobile phase impregnating the developed TLC plates.
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    Lee H. C. Chang T. Polymer Molecular Weight Characterization By Temperature Gradient High Performance Liquid Chromatography Polymer 1996 37 5747 5749
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    Polymer molecular weight characterization by temperature gradient high performance liquid chromatography
    Lee, Hee Cheong; Chang, Taihyun
    Polymer (1996), 37 (25), 5747-5749CODEN: POLMAG; ISSN:0032-3861. (Elsevier)
    We report a novel method of temp. gradient interaction HPLC for the characterization of mol. wt. distribution of macromols. A very fine and reproducible control of interaction between polymer chains and the packing material can be achieved by altering the column temp. A mixt. of 10 polystyrene samples (mol. wt. range: 1700-2,890,000) of narrow mol. wt. distribution are analyzed by this method. Near complete sepn. down to the baseline is achieved with the use of a single C18 bonded silica column. This method is thus proven to provide a much superior resoln. to the conventional size-exclusion chromatog.
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    Lee W. Lee H. Cha J. Chang T. Hanley K. J. Lodge T. P. Molecular weight distribution of polystyrene made by anionic polymerization Macromolecules 2000 33 5111 5115
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    Molecular weight distribution of polystyrene made by anionic polymerization
    Lee, Wonmok; Lee, Hyunjung; Cha, Junhoe; Chang, Taihyun; Hanley, Kenneth J.; Lodge, Timothy P.
    Macromolecules (2000), 33 (14), 5111-5115CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    A set of polystyrenes of varying mol. wts. was synthesized by anionic polymn. under identical conditions, and the mol. wt. distributions were critically examd. Polymn. of styrene was initiated with 2-butyllithium in cyclohexane at 45 °C. During the polymn., seven aliquots of the reaction mixt. were taken out at various reaction times using a cannula and terminated. The polymn. time varying mol. wts. and mol. wt. distributions of the polystyrenes were analyzed by temp. gradient interaction chromatog. (TGIC) as well as size exclusion chromatog. The mol. wt. distribution of the polystyrene approaches the Poisson distribution in the late stages of the polymn., in accordance with the early prediction of Flory. We also confirmed that the mol. wt. distribution of polystyrenes detd. by TGIC is close to the true value.
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    Chang T. Lee W. Lee H. C. Cho D. Park S. Polymer characterization by non-size exclusion chromatography: Temperature gradient interaction chromatography Am. Lab. 2002 34 39
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    Polymer characterization by non-size exclusion chromatography: temperature gradient interaction chromatography
    Chang, Taihyun; Lee, Wonmok; Lee, Hee Cheong; Cho, Donghyun; Park, Soojin
    American Laboratory (Shelton, CT, United States) (2002), 34 (14), 39-41CODEN: ALBYBL; ISSN:0044-7749. (International Scientific Communications, Inc.)
    Temp. gradient interaction chromatog. (TGIC) was used to characterize the mol. wt. distribution of various linear polystyrene (PS) stds. using a reversed-phase silica column. The temp. of the sepn. column is varied in a programmed way during elution to control the enthalpic interaction of polymeric solutes with the stationary phase. The app. for TGIC is a typical high performance liq. chromatog. instrument with modification to precisely control the temp. of the column and the mobile phase. Due to the high sensitivity to functional groups, two PS with identical MW except for a single hydroxyl end group difference were resolved. The MW sensitivity of TGIC also provides high resoln. in the anal. of branched polymers. TGIC also demonstrates a loading capacity much higher than SEC, which could be used to prep. extra high-quality primary and/or secondary std. polymers on a lab. scale.
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    Berek D. Liquid adsorption chromatography of copolymers: Molar mass (In)dependent retention Macromolecules 1999 32 3671 3673
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    Liquid Adsorption Chromatography of Copolymers: Molar Mass (In)dependent Retention
    Berek, D.
    Macromolecules (1999), 32 (11), 3671-3673CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Liq. adsorption chromatog. with a continuous solvent gradient elution has been shown by several authors to often sep. random and graft copolymers according to their chem. compn. whereas their molar masses do not play an important role. A tentative explanation of this finding is presented. It is assumed that the copolymer species travel along the column with a velocity which exactly corresponds with that of the eluent compn., exhibiting a displacing power just necessary to prevent a fast progress of the macromols. due to their exclusion. Under specific circumstances, retention of macromols. at this adsorption promoting "barrier" depends almost exclusively on the copolymer compn. and not on its molar mass. This hypothesis is based on the mechanism of the recently proposed and tested liq. chromatog. elution of homopolymers under limiting conditions of desorption and takes into account the simultaneous effect of adsorption and exclusion of macromols. onto/from the column packing.
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    Brun Y. The mechanism of copolymer retention in interactive polymer chromatography. I. Critical point of adsorption for statistical copolymers J. Liq. Chromatogr. Relat. Technol. 1999 22 3027 3065
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    The mechanism of copolymer retention in interactive polymer chromatography. I. Critical point of adsorption for statistical copolymers
    Brun, Y.
    Journal of Liquid Chromatography & Related Technologies (1999), 22 (20), 3027-3065CODEN: JLCTFC; ISSN:1082-6076. (Marcel Dekker, Inc.)
    A comprehensive anal. of interactive polymer chromatog. is presented. Isocratic liq. chromatog. of polymers at the crit. eluent compn. (the transition point where size-exclusion and adsorption interactions completely compensate each other) is currently used to sep. functional oligomers and block copolymers. We have extended the concept of this crit. elution chromatog. to the cases of statistical copolymers as well as porous stationary phases with heterogeneous surfaces (viz., surfaces with both inert and active groups). The theory provides the quant. condition for statistical copolymer chains to have a single adsorption-desorption transition point. The random copolymers with narrow chem. compn. distribution (CCD) always posses such a point. For non-random copolymers this condition includes the comparison between the mean length of chain segments connecting the attractive walls of the pore and the chem. correlation segment characterizing the randomness of the copolymer microstructure or the surface of this pore. If the crit. transition point exists, then the copolymer chains behave as hypothetical homopolymer chains with a single energy of interaction between the effective monomer units and the active groups at the surface. The relationship between this energy and the microstructure of copolymer chains has been also analyzed. If copolymer has a broad CCD, each compositionally homogeneous fraction has its own adsorption-desorption threshold. The partial transition points have been established for the copolymers with blocky or alternating microstructure. Only a portion of the copolymer chain effectively behaves as a homopolymer chain at these points. This property was used in the past for the sepn. of block copolymers according to the length of blocks comprised of the monomer units of a specific type.
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    Brun Y. The mechanism of copolymer retention in interactive polymer chromatography. II. Gradient separation J. Liq. Chromatogr. Relat. Technol. 1999 22 3067 3090
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    The mechanism of copolymer retention in interactive polymer chromatography. II. Gradient separation
    Brun, Y.
    Journal of Liquid Chromatography & Related Technologies (1999), 22 (20), 3067-3090CODEN: JLCTFC; ISSN:1082-6076. (Marcel Dekker, Inc.)
    The mol.-statistical theory of polymer solns. in confined media is applied to the conventional chromatog. theory of gradient elution. This approach leads to the prediction of the special mode of interactive polymer chromatog.: gradient elution at crit. point of adsorption. We demonstrate theor. and exptl. that under appropriate conditions elution of each compositionally homogeneous fraction of copolymer occurs at the crit. mobile phase compn. This crit. mobile phase compn. depends only on the local structure of the copolymer chain and is independent of its mol. wt. As a consequence, gradient elution produces the chem. compn. distribution of the copolymer. The theory provides the quant. conditions for statistical copolymer chains to have a single transition point. Equations describing relationships between the crit. eluent compn. and the chem. compn. and microstructure of macromols. are developed. The exptl. verification of the theory was performed by the normal phase isocratic and gradient elution of chlorinated polyethylene with various chem. compns. (chlorine content) and mol. wts. To the best of our knowledge, these expts., for the first time, demonstrate the existence of the adsorption-desorption transition point for statistical copolymers. The gradient sepn. at the crit. point of adsorption can be applied also to other complex polymers contg. various types of mol. heterogeneity.
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    Bashir M. A. Radke W. Predicting the chromatographic retention of polymers: Application of the polymer model to poly(styrene/ethylacrylate) copolymers J. Chromatogr. A 2012 1225 107 112
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    Predicting the chromatographic retention of polymers: Application of the polymer model to poly(styrene/ethylacrylate)copolymers
    Bashir, Mubasher A.; Radke, Wolfgang
    Journal of Chromatography A (2012), 1225 (), 107-112CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
    The retention behavior of a range of statistical poly(styrene/ethylacrylate) copolymers is investigated, in order to det. the possibility to predict retention vols. of these copolymers based on a suitable chromatog. retention model. It was found that the compn. of elution in gradient chromatog. of the copolymers is closely related to the eluent compn. at which, in isocratic chromatog., the transition from elution in adsorption to exclusion mode occurs. For homopolymers this transition takes place at a crit. eluent compn. at which the molar mass dependence of elution vol. vanishes. Thus, similar crit. eluent compns. can be defined for statistical copolymers. The existence of a crit. eluent compn. is further supported by the narrower peak width, indicating that the broad molar mass distribution of the samples does not contribute to the retention vol. It is shown that the existing retention model for homopolymers allows for correct quant. predictions of retention vols. based on only three appropriate initial expts. The selection of these initial expts. involves a gradient run and two isocratic expts., one at the compn. of elution calcd. from first gradient run and second at a slightly higher eluent strength.
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    Ryu J. Chang T. Thermodynamic prediction of polymer retention in temperature-programmed HPLC Anal. Chem. 2005 77 6347 6352
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    Thermodynamic Prediction of Polymer Retention in Temperature-Programmed HPLC
    Ryu, Jinsook; Chang, Taihyun
    Analytical Chemistry (2005), 77 (19), 6347-6352CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
    The polymer retention behavior in temp. gradient interaction chromatog. is investigated based on thermodn. consideration of the retention factor. The polymer retention predicted by the model calcn. is in good agreement with the exptl. results, and the model allows devising a temp. program for designed retention behaviors such as a linear dependence of retention vol. on log(mol. wt.) of polymers. In addn., the migration behavior of polymeric solute along the sepn. column can be simulated, which shows strong mol. wt. dependence. The migration behavior is also confirmed exptl. by employing different length columns or delayed injection.
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    Chang T. Polymer characterization by interaction chromatography J. Polym. Sci., Part B: Polym. Phys. 2005 43 1591 1607
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    Polymer characterization by interaction chromatography
    Chang, Taihyun
    Journal of Polymer Science, Part B: Polymer Physics (2005), 43 (13), 1591-1607CODEN: JPBPEM; ISSN:0887-6266. (John Wiley & Sons, Inc.)
    A review. Liq. chromatog. (LC) is a powerful tool for the characterization of synthetic polymers, that are inherently heterogeneous in mol. wt., chain architecture, chem. compn., and microstructure. Of different versions of the LC methods, size exclusion chromatog. (SEC) is most commonly used for the mol. wt. distribution anal. SEC separates the polymer mols. according to the size of a polymer chain, a well-defined function of mol. wt. for linear homopolymers. The same, however, cannot be said of nonlinear polymers or copolymers. Hence, SEC is ill suited for and inefficient in sepg. the mols. in terms of chem. heterogeneity, such as differences in chem. compn. of copolymers, tacticity, and functionality. For these purposes, another chromatog. method called interaction chromatog. (IC) is found as a better tool because its sepn. mechanism is sensitive to the chem. nature of the mols. The IC sepn. utilizes the enthalpic interactions to vary adsorption or partition of solute mols. to the stationary phase. Thus, it is used to sep. polymers in terms of their chem. compn. distribution or functionality. Further, the IC method has been shown to give rise to much higher resoln. over SEC in sepg. polymers by mol. wt. We present here our recent progress in polymer characterization with this method.
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    Lochmüller C. H. Moebus M. A. Liu Q. C. Jiang C. Elomaa M. Temperature Effect On Retention and Separation of Poly(Ethylene Glycol)S in Reversed-Phase Liquid Chromatography J. Chromatogr. Sci. 1996 34 69 76
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    Teramachi S. Matsumoto H. Kawai T. Direction of temperature gradient for normal-phase temperature gradient interaction chromatography in polystyrene fractionation J. Chromatogr. A 2005 1100 40 44
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    Direction of temperature gradient for normal-phase temperature gradient interaction chromatography in polystyrene fractionation
    Teramachi, Shinya; Matsumoto, Hiroshi; Kawai, Tadatomo
    Journal of Chromatography A (2005), 1100 (1), 40-44CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
    Temp. gradient interaction chromatog. (TGIC) is a powerful technique for mol. wt. fractionation of polymers, in which the interaction strength is controlled by varying the column temp. In the present paper, the effects of the sign of the temp. dependence of the retention and the direction of the temp. gradient (raising or lowering) on TGIC in the normal-phase mode were studied for the mol. wt. fractionation of polystyrene samples in org. mobile phases. It was found that a pos. temp. gradient was effective in the system consisting of amino-modified silica (NH2) column and the eluent mixt. of THF and n-hexane where retention decreased with increasing temp. A neg. temp. gradient was effective for the systems consisting of a bare-silica column//chloroform/n-hexane and NH2-column//chloroform/n-hexane, where retention increased with increasing temp. Increasing retention with increasing temp. has been found, so far, only for a water-sol. polymer (PEO) in an aq. mobile phase in RP-TGIC.
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    Matsumoto H. Kawai T. Teramachi S. Direction of temperature gradient and retention mechanism in normal-phase temperature gradient interaction chromatography for poly(methyl methacrylate) fractionation Polym. J. 2007 39 458 463
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    Direction of temperature gradient and retention mechanism in normal-phase temperature gradient interaction chromatography for poly(methyl methacrylate) fractionation
    Matsumoto, Hiroshi; Kawai, Tadatomo; Teramachi, Shinya
    Polymer Journal (Tokyo, Japan) (2007), 39 (5), 458-463CODEN: POLJB8; ISSN:0032-3896. (Society of Polymer Science, Japan)
    Temp. gradient interaction chromatog. (TGIC) is a powerful technique for mol. characterization of polymers, in which the interaction strength is controlled by varying the column temp. In the present paper, the direction of temp. gradient for normal-phase mode TGIC in poly(Me methacrylate) (PMMA) fractionation was studied by using System I (column: cyano-modified silica // eluent: 1,4-dioxane/n-hexane) and System II (bare silica // 1,4-dioxane/CH2Cl2), resp. It was found that PMMA samples were sepd. by pos. and neg. temp. gradients using the resp. systems. The results were also discussed theor.
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    Cho D. Park S. Hong J. Chang T. Retention mechanism of poly(ethylene oxide) in reversed-phase and normal-phase liquid chromatography J. Chromatogr. A 2003 986 191 198
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    Retention mechanism of poly(ethylene oxide) in reversed-phase and normal-phase liquid chromatography
    Cho, Donghyun; Park, Soojin; Hong, Jeongmin; Chang, Taihyun
    Journal of Chromatography, A (2003), 986 (2), 191-198CODEN: JCRAEY; ISSN:0021-9673. (Elsevier Science B.V.)
    The retention behavior of low- and high-mol.-mass poly(ethylene oxide) (PEO) in reversed-phase (RP) and normal-phase (NP) liq. chromatog. was investigated. In RPLC using a C18 bonded silica stationary phase and an acetonitrile-water mixt. mobile phase, the sorption process of PEO to the stationary phase showed ΔH°>0 and ΔS°>0. Therefore, PEO retention in RPLC sepn. is an energetically unfavorable, entropy-driven process, which results in an increase of PEO retention as the temp. increases. In addn., at the enthalpy-entropy compensation point the elution vol. of PEO was very different from the column void vol. These observations are quite different from the RPLC retention behavior of many org. polymers. The peculiar retention behavior of PEO in RPLC sepn. can be understood in terms of the hydrophobic interaction of this class of typical amphiphilic compds. with the non-polar stationary phase, on the one hand, and with the aq. mobile phase, on the other. The entropy gain due to the release of the solvated water mols. from the PEO chain and the stationary phase is believed to be responsible for the entropy-driven sepn. process. On the other hand, in NPLC using an amino-bonded silica stationary phase and an acetonitrile-water mixt. mobile phase, PEO showed normal enthalpy-driven retention behavior: ΔH°<0 and ΔS°<0, with the retention decreasing with increasing temp. and PEO eluting near the column void vol. at the enthalpy-entropy compensation point. Therefore, high-resoln. temp. gradient NPLC sepn. of high-mol.-mass PEO samples can be achieved with relative ease. The mol. mass distribution of high-mol.-mass PEO was found to be much narrower than that measured by size-exclusion chromatog.
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    Cong R. J. deGroot W. Parrott A. Yau W. Hazlitt L. Brown R. Miller M. Zhou Z. A New Technique for Characterizing Comonomer Distribution in Polyolefins: High-Temperature Thermal Gradient Interaction Chromatography (HT-TGIC) Macromolecules 2011 44 3062 3072
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    A new technique for characterizing comonomer distribution in polyolefins: high-temperature thermal gradient interaction chromatography (HT-TGIC)
    Cong, Rongjuan; de Groot, Willem; Parrott, Al; Yau, Wallace; Hazlitt, Lonnie; Brown, Ray; Miller, Matt; Zhou, Zhe
    Macromolecules (Washington, DC, United States) (2011), 44 (8), 3062-3072CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    This paper documents a new polyolefin characterization technique, high-temp. thermal gradient interaction chromatog. (HT-TGIC or TGIC), to quantify comonomer distribution. A set of homogeneous ethylene-octene homopolymers are used with a com. available column having a graphitic substrate (HYPERCARB) to demonstrate this technique's applicability to fractionating polyolefins. The sepn. mechanism appears to be based on the interaction of the polyolefin chains with the graphite surface upon a temp. change in an isocratic solvent. The TGIC technique overcomes the key issues encountered in crystn. based techniques and in high-temp. liq. chromatog. with a solvent gradient (HT-LC). Crystn. based techniques cover only a narrow anal. range of 0-9 mol % comonomer content and suffer from potential error in the anal. caused by cocrystn. effects. HT-LC is limited in its capability because of the limited choice in detectors available. Conversely, TGIC, because of the simplicity in solvent compn., has many com. available detectors, such as IR detectors (IR), light scattering detectors (LS), and viscometer detectors. For example, a triple detector TGIC with online IR, LS, and viscometer not only is capable of providing comonomer content and distribution from its TGIC retention temp. profile but also can provide a comprehensive microstructure mapping of mol. wt. (MW) and intrinsic viscosity (IV) across the comonomer distribution. Under the exptl. conditions used in this study, all these features can be obtained in a short anal. time of less than 1 h, for a comonomer content range of from 0 to 50 mol %. Addnl., TGIC is not subject to the cocrystn. problems that traditional polyolefins comonomer distribution characterization techniques have.
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    Lee H. C. Chang T. Characterization of Binary Polymer Mixtures by Simultaneous Size-Exclusion Chromatography and Interaction Chromatography Macromolecules 1996 29 7294 7296
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    Characterization of Binary Polymer Mixtures by Simultaneous Size Exclusion Chromatography and Interaction Chromatography
    Lee, Hee Cheong; Chang, Taihyun
    Macromolecules (1996), 29 (22), 7294-7296CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    We report a novel method to characterize binary polymer mixts. In this method, one component of a polymer mixt. is sepd. by a size exclusion mechanism and the other by an interactive mechanism simultaneously under single isocratic elution. For the effective sepn. by an interactive mechanism, the interaction strength between polymer chains and the packing material is controlled by programming the column temp. Using a series of three C18 bonded silica columns with different pore size and CH2Cl2/CH3CN mixt. as the mobile phase, we can sep. 10 polystyrene and 5 poly(Me methacrylate) stds. simultaneously in the interaction and the size exclusion region, resp. Resoln. of the method is found to be satisfactory.
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    Park S. Park I. Chang T. Ryu C. Y. Interaction-controlled HPLC for block copolymer analysis and separation J. Amer. Chem. Soc. 2004 126 8906 8907
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    Interaction-Controlled HPLC for Block Copolymer Analysis and Separation
    Park, Soojin; Park, Insun; Chang, Taihyun; Ryu, Chang Y.
    Journal of the American Chemical Society (2004), 126 (29), 8906-8907CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    An interaction-controlled HPLC technique was developed to analyze homopolymer precursors in block copolymer systems that are not easily identified by size exclusion chromatog. (SEC) and to obtain block copolymers that are homopolymer-free and compositionally narrower than the as-synthesized ones. We demonstrate that a "single peak" in SEC does not necessarily mean that the block copolymers are free of homopolymers (due to limitations in the SEC anal. of block copolymers) and propose to employ the interaction-controlled HPLC strategy for rigorous anal. and purifn. of block copolymers in terms of their chem. heterogeneity.
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    Park S. Cho D. Ryu J. Kwon K. Lee W. Chang T. Fractionation of block copolymers prepared by anionic polymerization into fractions exhibiting three different morphologies Macromolecules 2002 35 5974 5979
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    Fractionation of Individual Blocks of Block Copolymers Prepared by Anionic Polymerization into Fractions Exhibiting Three Different Morphologies
    Park, Soojin; Cho, Donghyun; Ryu, Jinsook; Kwon, Kyoon; Lee, Wonmok; Chang, Taihyun
    Macromolecules (2002), 35 (15), 5974-5979CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    In this study we fractionated a polystyrene-block-polyisoprene diblock copolymers (PS-b-PI) prepd. by anionic polymn. into fractions which have a narrower distribution in mol. wt. and in chem. compn. The strategy was to use two-dimensional HPLC: reversed phase HPLC to fractionate PI block and normal phase HPLC to fractionate PS block with a minimal effect of the other block. The working principle of the sepn. method was confirmed for a low mol. wt. PS-b-PI (2.4 kg/mol). With the aid of matrix assisted laser desorption/ionization mass spectrometry, we found that the sepn. method could resolve each mer of the PS-b-PI. We extended the application to a high mol. wt. diblock copolymer (24 kg/mol) and established the method as a promising tool to further fractionate block copolymers into mol. species better defined in mol. wt. and in compn. We obsd. a significant variation in av. mol. wt. and in compn. of the fractionated samples. These variations were large enough to show different morphologies for the fractions taken from the same mother block copolymer.
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    Chung B. H. Park S. Chang T. HPLC fractionation and surface micellization behavior of polystyrene-b-poly(methyl methacrylate) Macromolecules 2005 38 6122 6127
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    HPLC Fractionation and Surface Micellization Behavior of Polystyrene-b-poly(methyl methacrylate)
    Chung, Bonghoon; Park, Soojin; Chang, Taihyun
    Macromolecules (2005), 38 (14), 6122-6127CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    A polystyrene-block-poly(Me methacrylate) (PS-b-PMMA) was fractionated by HPLC, and the morphol. of surface micelles formed at the air/water interface was studied. Individual PS and PMMA blocks were fractionated by normal-phase and reversed-phase HPLC, resp., into three fractions each to obtain nine fractions of narrower distribution in mol. wt. and in compn. Although the mother PS-b-PMMA was prepd. by anionic polymn. and had a narrow mol. wt. distribution as characterized by size exclusion chromatog. (mol. wt. = 72.8 kg/mol, mol. wt./Mn = 1.08, PS% = 73.7%), the nine fractionated samples showed significant variations in mol. wt. (Mw = 63.1-79.5 kg/mol) and in compn. (PS% = 66.5-76.3%). The fractionated block copolymers formed more uniform surface micelles than the unfractionated mother PS-b-PMMA and exhibited a large variation with respect to the compn. The PS-b-PMMA fraction of the lowest PS content (66.5%) showed spherical micelles only. Rod-shaped micelles started to appear with a slight increase in the PS content, but circular and rod-shaped micelles coexist over ca. 10% concn. range and no sharp phase boundary appears to exist. The rod-shaped micelles formed at low PS contents exhibit a structure of linearly connected circular micelles.
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    Lee H. C. Lee W. Chang T. Yoon J. S. Frater D. J. Mays J. W. Linking-reaction kinetics of star shaped polystyrene by temperature gradient interaction chromatography Macromolecules 1998 31 4114 4119
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    Linking Reaction Kinetics of Star Shaped Polystyrene by Temperature Gradient Interaction Chromatography
    Lee, Hee Cheong; Lee, Wonmok; Chang, Taihyun; Yoon, Jin San; Frater, Donna J.; Mays, Jimmy W.
    Macromolecules (1998), 31 (13), 4114-4119CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    The linking reaction kinetics of a chlorosilane-linked polystyrene six-arm star was investigated by temp. gradient interaction chromatog. using a light scattering detector. The precursor arm material (Mw = 83,000) was made by anionic polymn. and end capped with isoprene, and 1,2-bis(trichlorosilyl)ethane was used as the linking agent. All the reaction intermediates, from unlinked arm to six-arm star, were successfully resolved from the aliquots taken from the reactor at various linking reaction times. From the time-varying relative abundance of the star mols. with different nos. of arms, linking reaction rate consts. were detd. The linking reaction rate becomes progressively slower as the no. of attached arms increases. We were able to ext. the quant. ratio of the linking rate consts., k5/k4 = 0.097 and k6/k5 = 0.30, where ki stands for the rate const. of the reaction incorporating the ith arm to an (i - 1)-arm star to form an i arm star. The larger value of k6/k5 than k5/k4 can be interpreted from the mol. structures of the linking agent and polymeric anions.
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    Ahn S. Lee H. Lee S. Chang T. Characterization of Branched Polymers by Comprehensive Two-Dimensional Liquid Chromatography with Triple Detection Macromolecules 2012 45 3550 3556
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    Characterization of Branched Polymers by Comprehensive Two-Dimensional Liquid Chromatography with Triple Detection
    Ahn, Seonyoung; Lee, Hyojoon; Lee, Sekyung; Chang, Taihyun
    Macromolecules (Washington, DC, United States) (2012), 45 (8), 3550-3556CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    In the branching anal. by size exclusion chromatog. (SEC)/triple detection (concn., light scattering, and viscosity detectors) method, the branch no. is calcd. from the extent of chain size contraction due to chain branching relative to the linear polymer of the same mol. wt. (MW). A problem can arise from the fact that polymer chain size depends on both MW and chain branching. Since SEC separates polymers according to the chain size, an SEC fraction of randomly branched polymers may contain polymer species heterogeneous in both MW and chain architecture in general. As a soln. of the problem, we propose a sepn. of polymers by interaction chromatog. according to MW first and then measure the chain size distribution of polymers in the homogeneous MW fraction by SEC/triple detection. The anal. scheme is successfully established by online two-dimensional liq. chromatog. combining temp. gradient interaction chromatog. and SEC/triple detection.
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    Cho D. Park S. Chang T. Ute K. Fukuda I. Kitayama T. Temperature gradient interaction chromatography and MALDI-TOF mass spectrometry analysis of stereoregular poly(ethyl methacrylate)s Anal. Chem. 2002 74 1928 1931
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    Temperature gradient interaction chromatography and MALDI-TOF mass spectrometry analysis of stereoregular poly(ethyl methacrylate)s
    Cho, Donghyun; Park, Soojin; Chang, Taihyun; Ute, Koichi; Fukuda, Iichiro; Kitayama, Tatsuki
    Analytical Chemistry (2002), 74 (8), 1928-1931CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
    Temp. gradient interaction chromatog. (TGIC) was applied for the sepn. of stereoregular poly(Et methacrylate) (PEMA) according to the tacticity. Three PEMA samples with differing tacticity (rr triad content: 0, 53, and 91%) prepd. by anionic polymn. were used. C18 bonded silica and a mixt. of CH2Cl2 and MeCN (30/70, vol./vol.) were used as stationary and mobile phase, resp. TGIC was able to sep. the PEMA samples, showing the increasing retention in the order of decreasing rr triad contents; however TGIC elution peaks of the three PEMAs were not fully resolved but, rather, were partially overlapped. To isolate the tacticity effect from the mol. wt. effect on the TGIC retention, the PEMA samples were fractionated by TGIC, and the accurate mol. wt. of the fractions was detd. by MALDI-TOF mass spectrometry. The fractions showed a much narrower mol. wt. distribution than the mother PEMAs. The TGIC fractions of similar mol. wt. but with different tacticity were fully resolved by TGIC, but mother PEMAs were not. These results indicate that the retention in TGIC is affected by both tacticity and mol. wt.
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    Perny S. Allgaier J. Cho D. Lee W. Chang T. Synthesis and Structural Analysis of an H-Shaped Polybutadiene Macromolecules 2001 34 5408 5415
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    Synthesis and Structural Analysis of an H-Shaped Polybutadiene
    Perny, Sebastien; Allgaier, Juergen; Cho, Donghyun; Lee, Wonmok; Chang, Taihyun
    Macromolecules (2001), 34 (16), 5408-5415CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    The synthesis of an H-shaped polybutadiene homopolymer as well as its detailed structural characterization is investigated. Anionic polymn. techniques together with chlorosilane linking agents were used for the prodn. of the material. After each reaction step samples were taken and analyzed by size exclusion chromatog. (SEC), membrane osmometry (MO), NMR, and temp. gradient interaction chromatog. (TGIC). According to the characterization by SEC, MO, and NMR, the H-polymer showed a high degree of structural uniformity after purifn. by fractionation, and no significant amts. of differently branched byproducts could be detected. The TGIC anal. however revealed the presence of large amts. of structures, mainly with lower branching degree. We also found that a significant isotope effect exists in the TGIC retention between deuterated and hydrogenous polymers. In our case, where the H-polymer is partially deuterated, the TGIC anal. enabled us to resolve all the side products. Comparison of the different anal. methods indicates that the precise structural anal. of branched model polymers such as the H-polymer requires more sophisticated methods than used in the past.
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    Ahn S. Im K. Chang T. Chambon P. Fernyhough C. M. 2D-LC Characterization of Comb-Shaped Polymers Using Isotope Effect Anal. Chem. 2011 83 4237 4242
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    2D-LC Characterization of Comb-Shaped Polymers Using Isotope Effect
    Ahn, Seonyoung; Im, Kyuhyun; Chang, Taihyun; Chambon, Pierre; Fernyhough, Christine M.
    Analytical Chemistry (Washington, DC, United States) (2011), 83 (11), 4237-4242CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
    A rigorous mol. characterization of comb-shaped polystyrene (PS) was carried out taking advantage of its mol. structure, a normal hydrogenous backbone, and deuterated side chains. Normal phase LC (NPLC) can sep. the comb PS species well according to their mol. wt. Nonetheless, it cannot distinguish the backbone from the side chains and the differently structured polymers having a similar mol. wt., e.g, a single backbone comb and a coupled backbone comb with fewer side chains. In contrast to NPLC, the hydrogenous polymer is retained longer than the deuterated counterpart in reversed phase LC (RPLC). When the isotope sensitivity of RPLC is taken advantage of, the comb PS is cross fractionated by NPLC and RPLC, and a two-dimensional mapping with respect to the backbone chain length and the no. of branches is fully established.
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    Berek D. Liquid chromatography of macromolecules under limiting conditions of desorption. 1. Principles of the method Macromolecules 1998 31 8517 8521
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    Liquid Chromatography of Macromolecules under Limiting Conditions of Desorption. 1. Principles of the Method
    Berek, D.
    Macromolecules (1998), 31 (24), 8517-8521CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    The liq. chromatog. of macromols. under limiting conditions of desorption (LC LCD) is based on a combination of exclusion and adsorption sepn. mechanisms. Eluent promotes desorption of macromols. that are dissolved in an adsorption-promoting liq. and injected into a liq. chromatog. (LC) column packed with porous adsorptive packing. The zone of sample solvent forms an "adsorption promoting barrier". Under properly chosen, "limiting", conditions the transport of adsorbing polymer species along the column is slowed since they cannot pass the above adsorption-promoting barrier. As result, macromols. of various sizes and molar masses leave LC column in the form of a rather narrow band immediately behind the zone of their initial solvent. At the same time, other kinds of polymer chains which exhibit lower affinity toward column packing and less adsorption surmount the zone of their original solvent. They are eluted in the size exclusion chromatog. mode. In this way macromols. with different chem. structures can be discriminated. The LC LCD idea has been tested with a model system comprising poly(Me methacrylate) probes, silica gel column packing, toluene (adsorbing liq.), and THF (desorbing liq.). Some applications of this novel LC procedure have been proposed. Include sepn. of two-component and multicomponent blends, various kinds of copolymers, and oligomers.
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    Rollet M. Pelletier B. Berek D. Maria S. Phan T. N. T. Gigmes D. Separation of parent homopolymers from polystyrene and poly(ethylene oxide) based block copolymers by liquid chromatography under limiting conditions of desorption-3. Study of barrier efficiency according to block copolymers’ chemical composition J. Chromatogr. A 2016 1462 63 72
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    Separation of parent homopolymers from polystyrene and poly(ethylene oxide) based block copolymers by Liquid Chromatography under Limiting Conditions of Desorption-3. Study of barrier efficiency according to block copolymers' chemical composition
    Rollet, Marion; Pelletier, Berengere; Berek, Dusan; Maria, Sebastien; Phan, Trang N. T.; Gigmes, Didier
    Journal of Chromatography A (2016), 1462 (), 63-72CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
    Liq. Chromatog. under Limiting Conditions of Desorption (LC LCD) is a powerful sepn. tool for multicomponent polymer systems. This technique is based on a barrier effect of an appropriate solvent, which is injected in front of the sample, and which decelerates the elution of selected macromols. In this study, the barrier effects have been evaluated for triblock copolymers polystyrene-b-poly(ethylene oxide)-b-polystyrene (PS-b-PEO-b-PS) according to the content of polystyrene (wt% PS) and PEO-block molar mass. PS-b-PEO-b-PS samples were prepd. by Atom Transfer Radical Polymn. (ATRP). The presence of resp. parent homopolymers was investigated by applying optimized LC LCD conditions. It was found that the barrier compn. largely affects the efficiency of sepn. and it ought to be adjusted for particular compn. range of block copolymers.
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    Chatterjee T. Rickard M. A. Pearce E. Pangburn T. O. Li Y. F. Lyons J. W. Cong R. J. deGroot A. W. Meunier D. M. Separating effective high density polyethylene segments from olefin block copolymers using high temperature liquid chromatography with a preloaded discrete adsorption promoting solvent barrier J. Chromatogr. A 2016 1465 107 116
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    Separating effective high density polyethylene segments from olefin block copolymers using high temperature liquid chromatography with a preloaded discrete adsorption promoting solvent barrier
    Chatterjee, Tirtha; Rickard, Mark A.; Pearce, Eric; Pangburn, Todd O.; Li, Yongfu; Lyons, John W.; Cong, Rongjuan; deGroot, A. Willem; Meunier, David M.
    Journal of Chromatography A (2016), 1465 (), 107-116CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
    Recent advances in catalyst technol. have enabled the synthesis of olefin block copolymers (OBC). One type is a "hard-soft" OBC with a high d. polyethylene (HDPE) block and a relatively low d. polyethylene (VLDPE) block targeted as thermoplastic elastomers. Presently, one of the major challenges is to fractionate HDPE segments from the other components in an exptl. OBC sample (block copolymers and VLDPE segments). Interactive high temp. liq. chromatog. (HTLC) is ineffective for OBC sepn. as the HDPE segments and block copolymer chains experience nearly identical enthalpic interactions with the stationary phase and co-elute. In this work we have overcome this challenge by using liq. chromatog. under the limiting conditions of desorption (LC LCD). A solvent plug (discrete barrier) is introduced in front of the sample which specifically promotes the adsorption of HDPE segments on the stationary phase (porous graphitic carbon). Under selected thermodn. conditions, VLDPE segments and block copolymer chains crossed the barrier while HDPE segments followed the pore-included barrier solvent and thus enabled sepn. The barrier solvent compn. was optimized and the chem. compn. of fractionated polymer chains was investigated as a function of barrier solvent strength using an online Fourier-transform IR (FTIR) detector. Our study revealed that both the HDPE segments as well as asym. block copolymer chains (HDPE block length » VLDPE block length) are retained in the sepn. and the barrier strength can be tailored to retain a particular compn. At the optimum barrier solvent compn., this method can be applied to sep. effective HDPE segments from the other components, which has been demonstrated using an exptl. OBC sample.
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    Liquid chromatography under limiting conditions of desorption 6: Separation of a four-component polymer blend
    Berek, Dusan; Macova, Eva
    Journal of Separation Science (2015), 38 (4), 543-549CODEN: JSSCCJ; ISSN:1615-9314. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Baseline sepn. was achieved of a model four-component polymer blend of polystyrene-poly(Me methacrylate)-poly(ethylene oxide)-poly(2-vinyl pyridine) in a single chromatog. run with help of the unconventional method of liq. chromatog. under limiting conditions of desorption. Narrow barriers of liqs. were employed, which selectively decelerated elution of particular kinds of macromols. Bare silica gel was the column packing, and the eluent was a mixt. of dimethylformamide/tetrahydrofuran/toluene 30:50:20 wt./wt./w. Barrier compns. were neat toluene, B#1, neat THF, B#2, and dimethylformamide/tetrahydrofuran/toluene 15:55:30, B#3. Minor blend constituents (∼1%) could be identified, as well. The result represents a step toward the sepn. and mol. characterization of triblock-copolymers, many of which are expected to contain besides both parent homopolymers also the diblock chains and thus they are in fact four-component polymer blends.
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    SEC-Gradients, an alternative approach to polymer gradient chromatography: 1. Proof of the concept
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    Polymer (2011), 52 (15), 3259-3262CODEN: POLMAG; ISSN:0032-3861. (Elsevier Ltd.)
    A new approach to gradient chromatog. of polymers is presented, in which the sample is introduced at the end of the gradient and elutes within the elution vol. range typical for size exclusion chromatog. (SEC). Due to the gradient the samples are retarded and elute nearly independent of molar mass at the adsorption threshold. The concept was proven for a series of narrowly distributed poly(Me methacrylate)s (PMMA) in a chloroform-tetrahydrofuran (THF) SEC-gradient. The application of the SEC-gradient to a blend of PMMA and polystyrene stds. of similar molar masses, which could not be sepd. by SEC due to their similar hydrodynamic sizes, resulted in a clear sepn. according to chem. compn. Since SEC-gradients allow dissolving the sample in strong eluents, which might result in breakthrough peaks in conventional gradients, the new approach is a valuable alternative to conventional gradient chromatog.
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    Maier H. Malz F. Reinhold G. Radke W. SEC Gradients: An Alternative Approach to Polymer Gradient Chromatography. Separation of Poly(methyl methacrylate-stat-methacrylic acid) by Chemical Composition Macromolecules 2013 46 1119 1123
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    SEC Gradients: An Alternative Approach to Polymer Gradient Chromatography. Separation of Poly(methyl methacrylate-stat-methacrylic acid) by Chemical Composition
    Maier, Helena; Malz, Frank; Reinhold, Guenter; Radke, Wolfgang
    Macromolecules (Washington, DC, United States) (2013), 46 (3), 1119-1123CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    The development of a chromatog. method capable to sep. poly(Me methacrylate-stat-methacrylic acid) samples with methacrylic acid contents of up to 50% by chem. compn. is described. For this purpose a gradient ranging from chloroform to dimethylacetamide on a PSS PROTEEMA column was applied. The application of a conventional gradient resulted in severe breakthrough peaks. Therefore, the recently developed concept of SEC gradients was used. No breakthrough peaks were obsd., and the peaks corresponding to samples of different content of methacrylic acid were well resolved. A nearly linear relationship between elution vol. and methacrylic acid content was obsd. The developed method allows detn. of the chem. compn. distribution of the above-mentioned class of polymers.
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    An equil. theory of polymer chromatog. was developed by using the model of a gaussian chain in a slitlike pore at arbitrary energies of interaction between the chain unit and the adsorbent and at any ratio of the chain size, R, to the pore width, D. Five specific regions existed in the chromatog. behavior of macromols., corresponding to different R and D values and different adsorption energies. Anal. expressions for the distribution coeff., K, were obtained for each region. The exptl. dependences of K on R were discussed.
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    A review. With the advance of polymer synthesis, polymers that possess unique architectures such as stars or cyclic chains, and unique chem. compn. distributions such as block copolymers or statistical copolymers have become frequently encountered. Characterization of these complex polymer systems drives the development of interactive chromatog. where the adsorption of polymers on the porous substrate in chromatog. columns is finely tuned. Liq. Chromatog. at the Crit. Condition (LCCC) in particular makes use of the existence of the Crit. Adsorption Point (CAP) of polymers on solid surfaces and has been successfully applied to characterization of complex polymer systems. Interpretation and understanding of chromatog. behavior of complex polymers in interactive chromatog. motivates theor./computational studies on the CAP of polymers and partitioning of these complex polymers near the CAP. This review article covers the theor. questions encountered in chromatog. studies of complex polymers.
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    Liquid chromatography under critical and limiting conditions: a survey of experimental systems for synthetic polymers
    Macko, Tibor; Hunkeler, David
    Advances in Polymer Science (2003), 163 (Liquid Chromatography FTIR Microspectroscopy Microwave Assisted Synthesis), 61-136CODEN: APSIDK; ISSN:0065-3195. (Springer-Verlag)
    A review on the sepn. of polymers by liq. chromatog. At the interface between the entropic size exclusion sepn. and the enthalpy-dominated liq. adsorption chromatog. it is possible, exptl., to identify conditions where polymer samples elute independent of their molar mass. These "crit. conditions" function according to theory by compensating the entropy and enthalpy of the sepn. For a series of common and specialty polymers, the mobile phase compns. and temp. which provide the molar mass independent elution behavior, for a given stationary phase, have been extd. from literature and summarized. This collection may help to select, or forecast, suitable LC systems, when an application of liq. chromatog. under crit. conditions for a polymer is required. Correlations between properties of solvents, sorbents and polymers, such as soly. parameters, eluotropic strength and Mark-Houwink consts. have been extd. from the collected data. Specifically, soly. parameters of crit. mobile phases corresponding to a pair polymer-sorbent are in a majority of cases very similar. The elution strength of the first component of a crit. binary eluent correlates linearly with the vol. percent of the second component, esp., when an identical packing gel is applied. However, the crit. conditions are independent of the thermodn. quality of the solvent. Under limiting conditions, the mobile phase may be even a precipitant or a strong adsorption promoting liq. for an injected polymer. Possibilities for increase of the upper molar mass sepn. limit are outlined and influence of sample solvent on elution behavior is described. Applications of liq. chromatog. under conditions of enthalpy-entropy compensation for sepn. of homo- and copolymers are also, briefly, summarized.
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    Chromatographic investigations of macromolecules in the critical range of liquid chromatography. 3. Analysis of polymer blends
    Pasch, H.
    Polymer (1993), 34 (19), 4095-9CODEN: POLMAG; ISSN:0032-3861.
    Polymer blends of various compns. were analyzed by liq. chromatog. at the crit. point of adsorption. By operating at the crit. point of one blend component, it is possible to sep. the blend regardless of the chem. structure and the molar mass of the second blend component. In addn., the molar mass and the molar-mass distribution of the second blend component may be detd. via a conventional size exclusion chromatog. procedure. It is shown that, in addn. to homopolymer blends, blends comprising a copolymer as one component may be sepd.
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    Pasch H. Rode K. Chaumien N. Chromatographic Investigations of Macromolecules in the Critical Range of Liquid Chromatography .9. Separation of Methacrylate-Based Polymer Blends Polymer 1996 37 4079 4083
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    Chromatographic investigations of macromolecules in the critical range of liquid chromatography. 9. Separation of methacrylate-based polymer blends
    Pasch, H.; Rode, K.; Chaumien, N.
    Polymer (1996), 37 (18), 4079-4083CODEN: POLMAG; ISSN:0032-3861. (Elsevier)
    Binary polymer blends of polymethacrylates were sepd. by liq. chromatog. at the crit. point of adsorption. The polymers were: poly(Me methacrylate) (PMMA), poly(t-Bu methacrylate) (PtBMA), poly(Bu methacrylate) (PnBMA), and poly(decyl methacrylate) (PDMA) and the mobile phase was methyl-Et ketone (MEK) and MEK-cyclohexane. By operating at chromatog. conditions corresponding to the crit. point of one blend component, the blends were sepd. regardless of the molar-mass distributions of the components. Depending on the polarity of the components, polar or non-polar stationary phases must be used. Operating at the crit. point of PMMA, less polar methacrylates can be analyzed using silica gel as the stationary phase and MEK-cyclohexane as the eluent. For the anal. of polar polymethacrylates at the crit. point of PDMA, a reversed stationary phase and tetrahydrofuran-acetonitrile are a useful combination.
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    Predicting the chromatographic retention of polymers: Poly(methyl methacrylate)s and polyacrylate blends
    Bashir, Mubasher A.; Radke, Wolfgang
    Journal of Chromatography A (2007), 1163 (1-2), 86-95CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
    The suitability of a retention model esp. designed for polymers is investigated to describe and predict the chromatog. retention behavior of poly(Me methacrylate)s as a function of mobile phase compn. and gradient steepness. It is found that three simple yet rationally chosen chromatog. expts. suffice to ext. the analyte specific model parameters necessary to calc. the retention vols. This allows predicting accurate retention vols. based on a min. no. of initial expts. Therefore, methods for polymer sepns. can be developed in relatively short time. The suitability of the virtual chromatog. approach to predict the sepn. of polymer blend is demonstrated for the first time using a blend of different polyacrylates.
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    Analysis of block copolymers by high-performance liquid chromatography under critical conditions
    Zimina, T. M.; Kever, J. J.; Melenevskaya, E. Yu.; Fell, A. F.
    Journal of Chromatography (1992), 593 (1-2), 233-41CODEN: JOCRAM; ISSN:0021-9673.
    The exptl. validity of the concept of so-called chromatog. "invisibility" in the complete chromatog. characterization of block copolymers (mol. wt. vs. chem. compn.), predicted theor. by Gorbunov and Skvortsov (1988) on the basis of the phenomenon of crit. conditions in liq. chromatog., was examd. The theor. approach predicts the possibility of 1 component of an A-B block copolymer being eluted under gel permeation chromatog. conditions, whereas the size of the alternate "invisible" component exerts no effect on the overall elution profile of the block copolymer. This applies only when special thermodn. conditions, i.e, eluent compn. and temp., are fulfilled, where the distribution coeff. is unity, regardless of mol. wt. Me methacrylate-styrene (I) block copolymers and I-tert-Bu methacrylate copolymer were used as examples with binary and ternary mixts. of acetonitrile-CH2Cl2, MeOH-CHCl3, THF-CH2Cl2, and THF-CH2Cl2-hexane as eluents for chromatog. under crit. conditions on wide-pore silica gel in narrow-bore columns.
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    Pasch H. Brinkmann C. Much H. Just U. Chromatographic investigations of macromolecules in the “critical range” of liquid chromatography II. Two-dimensional separations of poly(ethylene oxide-block-propylene oxide) J. Chromatogr. 1992 623 315
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    Pasch, H.; Brinkmann, C.; Much, H.; Just, U.
    Journal of Chromatography (1992), 623 (2), 315-22CODEN: JOCRAM; ISSN:0021-9673.
    An ethylene oxide-propylene oxide block copolymer (I) was characterized with respect to molar mass distribution and block length of the individual blocks using 2-dimensional chromatog. techniques. In the first dimension I was sepd. according to the length of the poly(propylene oxide) (II) block by liq. chromatog. at the crit. point of adsorption. The resulting II uniform fractions were subjected to supercrit. fluid chromatog. or size-exclusion chromatog. and the av. length and molar mass of the poly(ethylene oxide) blocks were detd. for every fraction.
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    Falkenhagen J. Much H. Stauf W. Muller A. H. E. Characterization of block copolymers by liquid adsorption chromatography at critical conditions. 1. Diblock copolymers Macromolecules 2000 33 3687 3693
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    Macromolecules (2000), 33 (10), 3687-3693CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Liq. adsorption chromatog. at crit. conditions (LACCC) in normal and in reversed-phase modes provides independent information on the molar mass distributions of both blocks of poly(Me methacrylate)-block-poly(tert-Bu methacrylate), even if no information about the precursor is available. In addn., the amt. of unreacted precursor can be detd., even if its molar mass is comparable to that of the total block copolymer. The reversal of elution order by changing of stationary and mobile phases makes it possible to independently characterize each block in the SEC mode of the LACCC system. Thus, complete structural information is obtained even without using two-dimensional chromatog. techniques.
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    Macromolecules (2001), 34 (7), 2353-2358CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    In the chromatog. sepn. of macromols. with a porous stationary phase, the retention is detd. by both size exclusion and interaction mechanisms. At the chromatog. crit. condition, the effects due to the 2 sepn. mechanisms compensate each other, and the retention of homopolymer mols. becomes independent of mol. wt. Liq. chromatog. at the crit. condition has attracted much interest for the characterization of block copolymers since it might permit the characterization of individual blocks of a block copolymer by making one block chromatog. invisible. This method is examd. using 2 sets of styrene-isoprene block copolymers designed to have one block length const. while varying the other block length. For these block copolymer systems, a block cannot be made completely invisible at the crit. condition of its homopolymer, and the retention of block copolymers is affected to some extent by the length of the invisible block under its chromatog. crit. condition.
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    Chromatographic investigations of macromolecules in the "critical range" of liquid chromatography. I. Functionality type and composition distribution in polyethylene oxide and polypropylene oxide copolymers
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    Polyoxyalkylenes obtained from ethylene oxide (I) and propylene oxide (II) and corresponding copolyethers were analyzed by liq. chromatog. under crit. conditions (near the crit. point of polymer adsorption) to obtain information on the functionality type distribution and structural inhomogeneity of copolymers. Homopolyether species were sepd. according to the no. and type of their end groups. Copolymers of I and II (random and block) were split into groups depending on chem. compn., block length, and the character of order in the monomer distribution.
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    The fractionation of functional polystyrene (PS) and poly(ethylene oxide) (PEOs) as well as their block copolymers, by liq. chromatog. at the exclusion adsorption transition point, also called crit. conditions mode, is reported. In this specific elution mode, the fractionation is only governed by the nature and the no. of functions attached to the polymer backbone, independent of the molar mass distribution of the whole sample. Functionally-terminated PS can be readily sepd. from non-functional PS under various chromatog. conditions. The technique also allows the fractionation of PEO and PS-PEO block copolymers. In the latter cases, moderately polar columns and water-based polar eluents were required to attain satisfactory fractionation.
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    Jiang X. L. Schoenmakers P. J. Lou X. W. Lima V. van Dongen J. L. J. Brokken-Zijp J. Separation and characterization of functional poly(n-butyl acrylate) by critical liquid chromatography J. Chromatogr. A 2004 1055 123 133
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    Journal of Chromatography A (2004), 1055 (1-2), 123-133CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
    The sepn. of functional poly(Bu acrylate) (PnBA) polymers based on the no. of end-groups under crit. liq. chromatog. (LC) conditions has been studied using a bare-silica column. The (near-) crit. solvent compns. for non-, mono-, and difunctional (telechelic) carboxyl-PnBAs were detd. in normal-phase LC, using mixts. of acetonitrile, acetic (or formic) acid, and dichloromethane of varying compn. Some formic or acetic acid had to be added to the mobile phase to elute PnBA polymers with carboxyl end-groups. The crit. solvent compns. obtained were not exactly the same for non-, mono-, and difunctional PnBA polymers. These were unusual exptl. observation, but they were in agreement with theoretic predictions. Nevertheless, low-mol.-mass PnBA samples were successfully sepd. according to the carboxyl functionality at (near-) crit. conditions. With the aid of mass spectrometry (MS), the (near-) crit. sepn. of low-mol.-wt. PnBA polymers was confirmed to be mainly based on the carboxyl functionality. Calibration curves for evaporative light-scattering detection (ELSD) were used for quant. anal. of carboxyl-functional PnBA polymers. The results proved that nearly ideal functionalities (av. no. of carboxyl end-groups per mol. up to 1.99) were achieved for telechelic PnBAs prepd. by one-step reversible addn.-fragmentation chain-transfer (RAFT) polymn. of PnBA.
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    Separation of branched polystyrene by comprehensive two-dimensional liquid chromatography
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    Journal of Chromatography A (2006), 1103 (2), 235-242CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
    Branched polystyrenes (PS) featuring a bivariate distribution in the mol. wt. and in the no. of branches were characterized by comprehensive two-dimensional liq. chromatog. (2D-LC). The branched PS were prepd. by anionic polymn. using BuLi as an initiator and a subsequent linking reaction with p-(chlorodimethylsilyl)styrene (CDMSS). The BuLi initiator yields polystyryl anions with broad mol. wt. distribution (MWD) and the linking reaction with CDMSS yields branched PS with different no. of branches. For the first dimension (1st-D) sepn., reversed-phase temp. gradient interaction chromatog. (RP-TGIC) was employed to sep. the branched polymer according to mainly the mol. wt. In the second dimension (2nd-D) sepn., the effluents from the RP-TGIC sepn. are subjected to liq. chromatog. at chromatog. crit. conditions (LCCC), in which the sepn. was carried out at the crit. condition of linear homo-PS to sep. the branched PS in terms of the no. of branches. The 2D-LC resoln. of RP-TGIC × LCCC combination worked better than the common LCCC × size-exclusion chromatog. (SEC) configuration due to the higher resoln. of RP-TGIC in mol. wt. than SEC. Furthermore, by virtue of using the same eluent in RP-TGIC and LCCC (only the column temp. is different), RP-TGIC × LCCC sepn. is free from possible 'break through' and large system peak problems. This type of 2D-LC sepn. could be utilized efficiently for the anal. of branched polymers with branching units distinguishable by LC sepn.
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    Petit C. Luneau B. Beaudoin E. Gigmes D. Bertin D. Liquid chromatography at the critical conditions in pure eluent: An efficient tool for the characterization of functional polystyrenes J. Chromatogr. A 2007 1163 128 137
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    Liquid chromatography at the critical conditions in pure eluent: An efficient tool for the characterization of functional polystyrenes
    Petit, Christelle; Luneau, Benoit; Beaudoin, Emmanuel; Gigmes, Didier; Bertin, Denis
    Journal of Chromatography A (2007), 1163 (1-2), 128-137CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
    Functional polymers are usually sepd. by liq. chromatog. at crit. conditions (LC-CC) using a desorli/adsorli mixt. as eluent. In this paper, we describe LC-CC using DMF as pure eluent at 72° and its application to the anal. of functional polystyrenes. The crit. adsorption point is reached by tuning the temp. so that the lack of repeatability is no longer a problem. We analyzed several batches of polystyrenes, exhibiting different mol. wts. and functionalities. We were able to differentiate di-, mono- and non-functional polystyrenes, bearing carboxylic acid, hydroxyl or nitroxide moieties. The behavior of these polystyrenes expressed by the exptl. results was compared with their behavior described by the LC-CC theory through the calcn. of the effective interaction parameter of each end group. The technique also makes it possible to quantify the fractions of different functional polymers in a blend.
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    Oh J. Kuk J. Lee T. Ye J. Paik H. J. Lee H. W. Chang T. Molecular Weight Distribution of Living Chains in Polystyrene Prepared by Atom Transfer Radical Polymerization ACS Macro Lett. 2017 6 758 761
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    Molecular Weight Distribution of Living Chains in Polystyrene Prepared by Atom Transfer Radical Polymerization
    Oh, Joongsuk; Kuk, Jiae; Lee, Taeheon; Ye, Jihwa; Paik, Hyun-jong; Lee, Hyo Won; Chang, Taihyun
    ACS Macro Letters (2017), 6 (7), 758-761CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
    Living and dead chains of a polystyrene synthesized by atom transfer radical polymn. were sepd. and characterized by high performance liq. chromatog. (HPLC), size exclusion chromatog. (SEC), NMR, and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The bromine end group in the living chain was quant. converted to a hydroxyl end group via first azidation and subsequent copper-catalyzed azide-alkyne cycloaddn. (CuAAC) click reaction with propargyl alc. The living chains bearing a polar end group are fully resolved from the unmodified dead chains by HPLC sepn. using a bare silica stationary phase. Mol. wt. distributions (MWD) of the living and dead chain are characterized by SEC and MALDI-MS. The MWD of the living chains is close to a Poisson distribution. Interestingly, the elution peak of the living chains in the HPLC sepn. split into two. The peak split is attributed to the diastereomeric structure of the chain end by NMR and MALDI-MS analyses.
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    Ahn J. Chang T. Wang X. Limpouchova Z. Prochazka K. Influence of the Chain Architecture and the Presence of End-Groups or Branching Units Chemically Different from Repeating Structural Units on the Critical Adsorption Point in Liquid Chromatography Macromolecules 2017 50 8720 8730
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    Influence of the Chain Architecture and the Presence of End-Groups or Branching Units Chemically Different from Repeating Structural Units on the Critical Adsorption Point in Liquid Chromatography
    Ahn, Junyoung; Chang, Taihyun; Wang, Xiu; Limpouchova, Zuzana; Prochazka, Karel
    Macromolecules (Washington, DC, United States) (2017), 50 (21), 8720-8730CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    The crit. adsorption point (CAP) of linear and star-shaped polymers was studied by normal phase and reversed phase liq. chromatog. (NPLC and RPLC) and computer simulation. Three sets of polystyrenes (PS) differing in chain architecture and chem. distinct groups were prepd.: linear PS (sec-Bu and hydrogen end group), 2-arm PS (linear, two sec-Bu end groups and one silyl group in the middle of the chain) and 4-arm star-shaped PS (four sec-Bu end groups and one silyl group in the center of the star). The column temp. at CAP, TCAP (linear PS) = TCAP (2-arm PS) > TCAP (4-arm PS) in both RPLC and NPLC which can be attributed to the variation in chain architecture. However, the elution times at CAP of three polymers are all different: In NPLC, tE,CAP (linear) > tE,CAP (2-arm PS) > tE,CAP (4-arm PS) while in RPLC, tE,CAP (4-arm PS) > tE,CAP (2-arm PS) > tE,CAP (linear). The variation of tE,CAP can be explained by the contribution of the chem. distinct groups. The computer simulation results are in good agreement with the chromatog. expts. results and support the interpretation of exptl. data.
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    Analysis of Macrocyclic Polystyrenes. 1. Liquid Chromatographic Investigations
    Pasch, Harald; Deffieux, Alain; Henze, Inka; Schappacher, Michel; Rique-Lurbet, Laurence
    Macromolecules (1996), 29 (27), 8776-8782CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Macrocyclic polystyrenes prepd. by a single-step, pseudo-unimol. cyclization of a linear α-(diethoxyethyl)-ω-styrenylpolystyrene can effectively be analyzed by liq. chromatog. at the crit. point of adsorption. Using silica gel as the stationary phase and THF-hexane as the eluent, the macrocyclic oligomers are sepd. from their linear precursors and other nonfunctional linear oligomers. The quant. detn. of the cyclization yield can be carried out via appropriate detector calibration for the linears and cyclics. Addnl. information on the chem. structure of the linears and cyclics is obtained by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. In conclusion, a possible cyclization mechanism is given including an interpretation of the MALDI behavior of the samples.
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    Lepoittevin B. Dourges M. A. Masure M. Hemery P. Baran K. Cramail H. Synthesis and characterization of ring-shaped polystyrenes Macromolecules 2000 33 8218 8224
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    Synthesis and Characterization of Ring-Shaped Polystyrenes
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    Macromolecules (2000), 33 (22), 8218-8224CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Macrocyclic polystyrenes were prepd. by coupling a two-ended living precursor dianions with 1,3-bis(1-phenylvinyl)benzene (DDPE). Expts. were performed in a dry box app., and macrocycles were obtained with a yield ranged between 40 and 55%. Simultaneously, besides the expected cyclic polymer, polycondensates (linear and cyclic) were formed. Thus, macrocyclic products were sepd. from the residual linear precursor and linear polycondensates byproducts by preparative high performance liq. chromatog. at the exclusion-adsorption transition point. Isolation of highly pure cyclic polystyrenes (of different sizes) was carried out. Information on the chem. structure of the linear and cyclic polystyrenes were obtained by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, showing a good agreement with the expected structures. In addn., viscometry measurements by SEC (viscometry detector) showed that the ratio g' = [η]C/[η]L is equal to 0.67 in a good solvent and confirmed the high efficiency of the preparative liq. chromatog. sepn.
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    Lee H. C. Lee H. Lee W. Chang T. Roovers J. Fractionation of cyclic polystyrene from linear precursor by HPLC at the chromatographic critical condition Macromolecules 2000 33 8119 8121
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    Fractionation of Cyclic Polystyrene from Linear Precursor by HPLC at the Chromatographic Critical Condition
    Lee, Hee Cheong; Lee, Hyunjung; Lee, Wonmok; Chang, Taihyun; Roovers, Jacques
    Macromolecules (2000), 33 (22), 8119-8121CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    The fractionation of cyclic polystyrene from linear contaminants by HPLC at the crit. condition is reported.
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    Lee W. Lee H. Lee H. C. Cho D. Chang T. Gorbunov A. A. Roovers J. Retention Behavior of linear and ring polystyrene at the chromatographic critical condition Macromolecules 2002 35 529 538
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    Retention Behavior of Linear and Ring Polystyrene at the Chromatographic Critical Condition
    Lee, Wonmok; Lee, Hyunjung; Lee, Hee Cheong; Cho, Donghyun; Chang, Taihyun; Gorbunov, Alexei A.; Roovers, Jacques
    Macromolecules (2002), 35 (2), 529-538CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Chromatog. retention of linear and ring polystyrene was studied near the chromatog. crit. condition. Reversed phase silica columns of four different pore sizes were employed to examine the pore size dependence. Adjusting the column temp., the crit. condition for linear polystyrene was searched for each column with a mixed mobile phase of CH2Cl2/CH3CN (57/43 vol./vol.). It was practically impossible to establish an unambiguous crit. condition with a single pore size column for a wide mol. wt. range of polystyrenes, in particular with narrow pore size columns. At the best available condition, retentions of nine different mol. wt. ring polystyrenes were measured relative to their linear precursors for each pore-sized column. As predicted theor., the partition coeff. (K) of ring polymers vs. the size ratio of polymer chain to pore (R/d) shows a good linear relation in the large pore regime (R/d « 1). This linearity is universal for all the pore sizes, which is consistent with the theor. prediction. However, the K vs. R/d dependency at the large pore regime did not follow the theor. prediction quant. In the narrow-pore regime (R/d » 1) the exptl. results did not follow the theory for ideal-chain ring macromols. even qual. To explain the obsd. chromatog. behavior at R/d » 1, the scaling theory accounting for the polymer excluded vol. was used, and the definition of the crit. condition was revised. This anal. gave some keys for understanding the results at R/d » 1 and revealed the possible nonequivalence of the conditions for theory and expt. as the most probable reason for obsd. discrepancies.
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    Takano A. Kushida Y. Aoki K. Masuoka K. Hayashida K. Cho D. Kawaguchi D. Matsushita Y. HPLC Characterization of Cyclization Reaction Product Obtained by End-to-End Ring Closure Reaction of a Telechelic Polystyrene Macromolecules 2007 40 679 681
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    HPLC Characterization of Cyclization Reaction Product Obtained by End-to-End Ring Closure Reaction of a Telechelic Polystyrene
    Takano, Atsushi; Kushida, Yuuki; Aoki, Kayoko; Masuoka, Keisuke; Hayashida, Kenichi; Cho, Donghyun; Kawaguchi, Daisuke; Matsushita, Yushu
    Macromolecules (2007), 40 (3), 679-681CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Cyclization reaction product synthesized by the end-to-end ring closure reaction of a telechelic polystyrene with mol. wt. of 38K in extremely dil. conditions was carefully characterized by using two kinds of HPLC techniques, i.e., liq. chromatog. at the crit. condition (LCCC) and size exclusion chromatog. (SEC). First, the cyclization reaction product was coarsely sepd. into linear species and cyclic ones by LCCC; second, each fraction was further sepd. by high-resoln. SEC. It was found from the HPLC analyses that the cyclization reaction product contains both linear and cyclic condensation products. Furthermore, dimeric, trimeric, and more multimeric cyclic mols. with reasonable abundance were identified as well as the monomeric cyclic mol. with high yield, as much as 50%, in the cyclic products.
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    Kapnistos M. Lang M. Vlassopoulos D. Pyckhout-Hintzen W. Richter D. Cho D. Chang T. Rubinstein M. Unexpected power-law stress relaxation of entangled ring polymers Nat. Mater. 2008 7 997 1002
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    Unexpected power-law stress relaxation of entangled ring polymers
    Kapnistos, M.; Lang, M.; Vlassopoulos, D.; Pyckhout-Hintzen, W.; Richter, D.; Cho, D.; Chang, T.; Rubinstein, M.
    Nature Materials (2008), 7 (12), 997-1002CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
    Long linear and branched polymers have a characteristic entanglement plateau and stress relaxation proceeds by chain reptation or branch retraction. In both mechanisms, the presence of chain ends is essential. Properly purified high-mol. wt. ring polystyrene, exhibits self-similar dynamics, yielding a power-law stress relaxation. However, trace amts. of linear polymer chains at a concn. almost two decades below the overlap caused an enhanced mech. response. An entanglement plateau was recovered at higher concns. of linear chains. The results are useful as a tool for manipulation of properties of polymers and for tuning the rheol. of entangled polymers.
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    Analysis of complex polymers by multidimensional techniques. Invited Lecture
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    Physical Chemistry Chemical Physics (1999), 1 (17), 3879-3890CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    A review with 53 refs. Complex polymers are distributed in more than one way in terms of mol. heterogeneity. In addn. to the molar mass distribution, they are frequently distributed with respect to chem. compn., functionality, mol. architecture. For the characterization of the different types of mol. heterogeneity it is necessary to use a wide range of anal. techniques. Preferably, these techniques should be selective towards a specific type of heterogeneity. The combination of 2 selective anal. techniques is assumed to yield 2-dimensional information on the mol. heterogeneity. The principles of combining different anal. techniques in multidimensional anal. schemes are discussed. The most promising protocols for coupled techniques are the combination of 2 different chromatog. methods and the combination of chromatog. and spectroscopy. The basic principles of 2-dimensional chromatog. are considered, combining interaction chromatog. and size exclusion chromatog. In the use of liq. chromatog. with selective detectors, the coupling of different chromatog. techniques with Fourier-transform IR and NMR spectroscopies and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry is highlighted.
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    Kilz P. Two-dimensional chromatography as an essential means for understanding macromolecular structure Chromatographia 2004 59 3 14
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    Two-dimensional chromatography as an essential means for understanding macromolecular structure
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    Chromatographia (2004), 59 (1/2), 3-14CODEN: CHRGB7; ISSN:0009-5893. (Vieweg Verlag/GWV Fachverlage GmbH)
    A review. Current liq. chromatog. techniques allow to det. distributions of various properties for macromols. The polydisperse nature of macromols. regulates the structure-property relationship and is responsible for the vast degree of fine-tuning of application properties. The understanding of macromol. structure is fundamental for the use of polymers in increasingly specific applications. The coexistence of property distributions requires multi-dimensional (combined) chromatog. methodologies. The use and implementation of two-dimensional (2D) sepn. methods and their benefits are described in this paper for synthetic polymers. Similar approaches were used successfully for mapping complex natural and bio-polymers.
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    Berek D. Two-dimensional liquid chromatography of synthetic polymers Anal. Bioanal. Chem. 2010 396 421 441
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    Two-dimensional liquid chromatography of synthetic polymers
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    Analytical and Bioanalytical Chemistry (2010), 396 (1), 421-441CODEN: ABCNBP; ISSN:1618-2642. (Springer)
    A review. Two-dimensional liq. chromatog., 2D-LC of synthetic polymers is critically assessed. Similarities and differences of 2D-LC of low-mol.-mass and polymeric substances are reviewed. The rationale of application of 2D-LC to macromol. substances is discussed. Basic information on retention mechanisms in liq. chromatog. of synthetic polymers is furnished. The principles, reasons, and significance of coupling of retention mechanisms are explained. The resulting sepn. processes are elucidated, and the tech. concepts of the corresponding exptl. arrangements are described. The benefits of 2D-LC are demonstrated together with numerous problems and shortcomings of the method. Figure Schematic diagram of contour plot of the results of 2D-LC sepn. A complex polymer system contains three constituents, each with both compn. and molar mass distribution. Sample concn. is visualized by use of color, with concn. increasing from blue to yellow.
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    Baumgaertel A. Altuntaş E. Schubert U. S. Recent developments in the detailed characterization of polymers by multidimensional chromatography J. Chromatogr. A 2012 1240 1 20
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    Recent developments in the detailed characterization of polymers by multidimensional chromatography
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    Journal of Chromatography A (2012), 1240 (), 1-20CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
    A review. Synthetic polymers as well as biopolymers reveal complex structures, such as variations in functionality, chain length and architecture. Therefore, combinations of different chromatog. techniques are a prerequisite for a detailed characterization. One possible approach is the combination of high performance liq. chromatog. at crit. conditions (LCCC) and size-exclusion chromatog., also named as two-dimensional chromatog., which allows the sepn. of the polymers according to different properties, like molar mass, chem. compn. or functionality. In addn., LCCC hyphenated with different mass spectrometry techniques, e.g. MALDI-TOF or ESI-TOF, leads to addnl. information about mol. details of the polymeric structure. We summarize in this article the recent developments in two-dimensional chromatog. of synthetic polymers and biopolymers since 2005.
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    Multi-Dimensional Separations of Polymers
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    Analytical Chemistry (Washington, DC, United States) (2014), 86 (13), 6172-6179CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
    Synthetic polymers and comprehensive two-dimensional liq. chromatog. (LC×LC) are a synergistic combination. LC×LC provides unique insights in mutually dependent mol. distributions. Synthetic polymers offer clear demonstrations of the value of LC×LC.
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    Jiang X. L. van der Horst A. Schoenmakers P. J. Breakthrough of polymers in interactive liquid chromatography J. Chromatogr. A 2002 982 55 68
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    Breakthrough of polymers in interactive liquid chromatography
    Jiang, Xulin; van der Horst, Aschwin; Schoenmakers, Peter J.
    Journal of Chromatography A (2002), 982 (1), 55-68CODEN: JCRAEY; ISSN:0021-9673. (Elsevier Science B.V.)
    Two sep. peaks are obsd. for narrow polymer stds. in both isocratic and gradient HPLC. One peak appears around the solvent front (the solvent-plug peak or breakthrough peak), whereas the 2nd peak is retained significantly-or even highly. Although the effect was obsd. many times before, it has never been rigorously explained. The authors provide a detailed explanation for the breakthrough peak. The two completely sep. peaks are demonstrated not to represent to different fractions of the sample (e.g., the low- and high-mol.-mass parts of the distribution). Both peaks are representative of the entire polymeric sample for narrow polymer std. Because the amt. of the polymer in the breakthrough peak may vary, the quant. anal. of the polymers by LC is jeopardized. The effects of the sample solvent, the (initial) mobile phase compn., the injection vol., the injected sample concn., the column temp., and the analyte structure and mol. mass on the breakthrough peak were studied in LC expts. involving stds. of polystyrene and poly(Me methacrylate). Three necessary and sufficient conditions are suggested for the breakthrough phenomenon to be obsd. Recommendations to avoid the breakthrough phenomenon are given, culminating in a structured method for selecting the best possible sample solvents.
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    Gerber J. Radke W. Separation of linear and star-shaped polystyrenes by two-dimensional chromatography E-Polymers 2005
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    Pasch H. Kilz P. Fast liquid chromatography for high-throughput screening of polymers Macromol. Rapid Commun. 2003 24 104 108
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    Fast liquid chromatography for high-throughput screening of polymers
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    Macromolecular Rapid Communications (2003), 24 (1), 104-108CODEN: MRCOE3; ISSN:1022-1336. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Liq. chromatog. of polymers is traditionally a slow technique with anal. times of typically 30 min per sample. For the application of liq. chromatog. techniques to combinatorial materials research the anal. time per sample must be reduced considerably. Anal. time in SEC can be reduced to about 2 min per sample when high-throughput columns are used. For HPLC small columns with improved sepn. efficiencies can be used. As compared to conventional technol., time savings of more than 80% are achieved.
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    Popovici S. T. Schoenmakers P. J. Fast size-exclusion chromatography - Theoretical and practical considerations J. Chromatogr. A 2005 1099 92 102
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    Fast size-exclusion chromatography-Theoretical and practical considerations
    Popovici, Simona T.; Schoenmakers, Peter J.
    Journal of Chromatography A (2005), 1099 (1-2), 92-102CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
    Fast SEC is a very interesting modification of conventional SEC. The need for it emerges from combinatorial chem. and high-throughput experimentation, where high-speed analyses are required. The different approaches to change the speed of anal. are extensively described. Special attention is paid to the trade-off between anal. time and resoln. and to the selection of optimal column lengths and flow rates. Simulations were used to design and to understand expts. Integrity plots are constructed to judge the quality of various SEC systems. Fast sepns. in size-exclusion chromatog. are more favorable than suggested by conventional theory. The results are based on exptl. data obtained for polystyrene using THF as mobile phase.
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    High temperature size exclusion chromatography
    Cho, Heesook; Park, Soojin; Ree, Moonhor; Chang, Taihyun; Jung, Jin Chul; Zin, Wang Cheol
    Macromolecular Research (2006), 14 (3), 383-386CODEN: MRAECT; ISSN:1598-5032. (Polymer Society of Korea)
    High-temp. size exclusion chromatog. (SEC) was used widely for the characterization of cryst. polymers, for which high temp. operation above the polymer melting temp. is required to dissolve the polymers. However, this high temp. operation has many advantages in SEC sepn. in addn. to merely increasing polymer soly. At high temp. the eluent viscosity decreases, which in turn decreases the column back-pressure and increases the diffusivity of the analytes. Therefore, many reports on the high temp. operation of HPLC have focused on shortening the anal. time and enhancing the resoln. However, the application of high temp. SEC anal. to exploit the merits of high temp. operation is scarce. Therefore, it is reported on a new app. design for high temp. SEC.
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    Fast and efficient size-based separations of polymers using ultra-high-pressure liquid chromatography
    Uliyanchenko, Elena; Schoenmakers, Peter J.; van der Wal, Sjoerd
    Journal of Chromatography A (2011), 1218 (11), 1509-1518CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
    Ultra-high-pressure liq. chromatog. (UHPLC) has great potential for the sepns. of both small mols. and polymers. However, the implementation of UHPLC for the anal. of macromols. invokes several problems. First, to provide information on the mol.-wt. distribution of a polymer, size-exclusion (SEC) columns with specific pore sizes are needed. Development of packing materials with large pore diams. and pore vols. which are mech. stable at ultra-high-pressures is a technol. challenge. Addnl., narrow-bore columns are typically used in UHPLC to minimize the problem of heat dissipation. Such columns pose stringent requirements on the extra-column dispersion, esp. for large (slowly diffusing) mols. Finally, UHPLC conditions generate high shear rates, which may affect polymer chains. The possibilities and limitations of UHPLC for size-based sepns. of polymers are addressed in the present study. We demonstrate the feasibility of conducting efficient and very fast size-based sepns. of polymers using conventional and wide-bore (4.6 mm I.D.) UHPLC columns. The wider columns allow minimization of the extra-column contribution to the obsd. peak widths down to an insignificant level. Reliable SEC sepns. of polymers with mol. wts. up to ca. 50 kDa are achieved within less than 1 min at pressures of about 66 MPa. Due to the small particles used in UHPLC it is possible to sep. high-mol.-wt. polymers (50 kDa ≤ M r ≤ 1-3 MDa, upper limit depends on the flow rate) in the hydrodynamic-chromatog. (HDC) mode. Very fast and efficient HDC sepns. are presented. For very large polymer mols. (typically larger than several MDa, depending on the flow rate) two chromatog. peaks are obsd. This is attributed to the onset of mol. deformation at high shear rates and the simultaneous actions of hydrodynamic and slalom chromatog.
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    Journal of Chromatography A (2009), 1216 (21), 4606-4610CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
    In recent years, two-dimensional liq. chromatog. (2D-LC) was used increasingly for the anal. of synthetic polymers. A 2D-LC anal. provides richer information than a single chromatog. anal. at the cost of longer anal. time. The time required for a comprehensive 2D-LC anal. is essentially proportional to the anal. time of the second dimension sepn. Many of 2D-LC analyses of synthetic polymers have employed size exclusion chromatog. (SEC) for the second-dimension anal. due to the relatively short anal. time in addn. to the wide use in the polymer anal. Nonetheless, short SEC columns are often used for 2D-LC analyses to reduce the sepn. time, which inevitably deteriorates the resoln. In this study, we demonstrated that high temp. SEC can be employed as an efficient second-LC in the 2D-LC sepn. of synthetic polymers. By virtue of high temp. operation (low solvent viscosity and high diffusivity of the polymer mols.), a normal length SEC column can be used at high flow rate with little loss in resoln.
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    Comprehensive Two-Dimensional Liquid Chromatography Analysis of a Block Copolymer
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    Analytical Chemistry (2007), 79 (3), 1067-1072CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
    A two-dimensional liq. chromatog. (2D-LC) method, normal phase liq. chromatog. (NPLC) for one dimension and reversed phase liq. chromatog. (RPLC) for the other dimension, was employed to map the mol. wt. distribution (MWD) of the individual blocks of a polystyrene-block-polyisoprene (PS-b-PI) diblock copolymer. The first-dimension (1st-D) NPLC separates PS-b-PI according to the PS block length while the second-dimension (2nd-D) RPLC separates PS-b-PI according to the PI block length. For the first-dimension NPLC sepn., the column temp. was controlled to improve the resoln. while the 2nd-D RPLC was run isothermally to reduce the sepn. time. The MWD information of individual blocks provides equiv. information to MWD and chem. compn. distribution of a block copolymer. In this anal., the effluent from the 1st-D LC sepn. is concd. before the injection to the 2nd-D LC by use of a trap column, which allows an efficient interface between the two LC sepns. Over 200 different block copolymer species could be identified from the 2D-LC chromatogram.
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    One- and Two-Dimensional Chromatographic Analysis of Alcohol Ethoxylates
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    Analytical Chemistry (1998), 70 (20), 4353-4360CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
    Two-dimensional liq. chromatog. (2DLC) is an increasingly popular technique which has the potential to provide a far more detailed sepn. and characterization of alc. ethoxylates (AE) than was shown by previously used sepn. techniques. The AE are unique in that these mols. have distributions in both alkyl and ethylene oxide chain lengths. The single-column techniques of open-tubular SFC, normal- and reversed-phase HPLC, and the multiple column technique of 2DLC are compared in terms of the efficacy of sepn. and characterization of the alkyl and ethoxylate distributions in a select group of AE. The combination of normal- and reversed-phase HPLC in a 2DLC system accomplishes the simultaneous alkyl and ethylene oxide distribution anal. The advantage of using 2DLC over one-dimensional chromatog. techniques is clearly demonstrated in the increased selectivity resulting in the ability to produce the ethylene oxide distributions of each alkyl component in an AE. In addn., 2DLC chromatograms are easier to interpret due to ordering of the chromatograms.
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  • Figure 1

    Figure 1. Chromatograms of six polystyrene standards (Mw: (1) 2.5k, (2) 12k, (3) 29k, (4) 165k, (5) 502k, (6) 1,800k). Single column (Nucleosil C18; 250 x 4.6 mm, 5 μm particle, 100 Å pore) was used and the flow rate was 0.5 mL/min. (Left) Solvent composition effect at a fixed column temperature of 30.5°C with the mixed eluents of CH2Cl2/CH3CN at different compositions as labeled in the plot. (Right) Temperature effect at a fixed eluent composition of 57/43 (v/v). The isothermal chromatograms were obtained at different column temperatures as labeled in the plot. The CAP condition is established at the composition of CH2Cl2/CH3CN = 57/43 (v/v) and the column temperature of 30.5°C. The vertical dashed lines indicate the elution time of the injection solvent peak.
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    From reference ( 14). This figure was reproduced with permission of Wiley and Sons.

    Figure 2

    Figure 2. Temperature Gradient Interaction Chromatography (TGIC) separation of 14 standard polystyrenes showing the high resolution separation of IC. The column temperature program is shown in the plot. Mobile phase was a mixture of CH2Cl2/CH3CN (57/43, v/v). Single C18 bonded silica column (Nucleosil C18, 250 x 2.1 mm, 5 μm, 100 Å) was used and the flow rate was 0.1 mL/min. TGIC shows much lower Mw/Mn values than SEC indicating higher resolution of IC than SEC.
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    From reference ( 24). This figure was reproduced with permission from American Laboratory.

    Figure 3

    Figure 3. TGIC separation of a mixture of 10 polystyrene (a-k: 1.7k, 5.1k, 11.6k, 22.0k, 37.3k, 68.0k, 114k, 208k, 502k, 1090k, 2890k) and 5 poly(methyl methacrylate) (1-5: 1500k, 501k, 77.5k, 8.5k, 2.0k) standards. S is the injection solvent peak. The temperature program is also shown in the plot. Three columns (Nucleosil C18, 250 x 4.5 mm, 100Ǻ & 500 Ǻ & 1,000Ǻ) are used and the mobile phase is a mixture of CH2Cl2/CH3CN(54/46 (v/v)).
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    From reference ( 38).

    Figure 4

    Figure 4. LCCC chromatograms of cyclic PSs and corresponding linear precursors at the CAP of linear PS. Linear precursors elute at about the same retention time (5.4 min) independent of the MW while the retention of cyclic polymer increases with molecular weight. The small peaks appearing near tR = 5 min are the injection solvent peaks. The elution peak of cyclic polymers is completely separated from the linear precursors down to the baseline. The chromatograms of cyclic PS (black line) show that most of the samples contain contaminants, mostly the linear precursors.
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    From reference ( 77).

    Figure 5

    Figure 5. 2D-LC chromatograms recorded by a UV absorption detector (260 nm) showing polymer MW (SEC) vs. 1st-D LC retention time at different column temperatures; SEC (T = 63.0 °C), LCCC (T = 37.2 °C), IC (T = 28.0 °C). PS standards: 3.3k, 10k, 31k, 113k, 384k, 1800k. 1st-D IC (abscissa): Nucleosil C18 150 x 4.6 mm, 7 μm, 500 Å); Eluent: CH2Cl2/CH3CN = 57/43 (v/v); Flow rate: 0.05 mL/min. 2nd-D SEC (ordinate): PL PolyPore (250 × 4.6 mm); Eluent: THF; Flow rate: 1.7 mL/min; Column temperature: 110 °C.
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    From the reference ( 92). This figure was reproduced with permission from Elsevier.

    Figure 6

    Figure 6. NP-TGIC × RPLC 2D-LC chromatogram of a low MW polystyrene-block-polyisoprene (1.7k-0.7k, Mw/Mn: 1.06) (1st-D NP-TGIC: Nucleosil Diol, 250 x 7.8 mm, 7 μm, 100 Å, Eluent: isooctane/THF=97/3 (v/v); Flow rate: 0.05 mL/min. 2nd-D RPLC: Kromasil C18, 150 x 4.6 mm, 5 μm, 100 Å, Eluent: CH2Cl2/CH3CN=53/47 (v/v), Flow rate: 1.1 mL/min, Trap column: Alltech C18, 3 μm, 100 Å, 33 × 70 mm).
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    From reference ( 93).

  • References

    CHAPTER SECTIONS
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    This chapter references 94 other publications.

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      Striegel, A. M.; Yau, W. W.; Kirkland, J. J.; Bly, D. D. Modern Size-Exclusion Chromatography, Practice of Gel Permeation Chromatography and Gel Filtration Chromatography; Wiley: Hoboken, 2009.
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      A review. Size exclusion chromatog., SEC is one of the most popular methods for the sepn. of different kinds of macromols. This crit. review gives concise information about macromols. and their behavior in soln., basic understanding about principles, instrumentation, and application possibilities of SEC, and more in detail discusses drawbacks and pitfalls of the method with the emphasis on synthetic polymers. Selected practical advices are included to help enhance the quality of SEC results.
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      The title subject is discussed, with the use of math. models, to det. why gel permeation chromatog. sep. macromols. on the basis of size. The distribution coeff. for mols. in soln. and in voids (spherical, cyclindrical, and rectangular) is detd. math. and agrees with data for permeation of porous glass by polystyrenes in a 2-component θ solvent.
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      Grubisic Z. Rempp P. Benoit H. A Universal Calibration for Gel Permeation Chromatography Polym. Lett. 1967 5 753 759
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      Tung L. H. Method of Calculating Molecular Weight Distribution Function from Gel Permeation Chromatograms J. Appl. Polym. Phys. 1966 10 375 385
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      Method of calculating molecular-weight-distribution functions from gel-permeation chromatograms
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      An integral equation taking into account the limited resolution of chromatographic columns is given to relate the gel-permeation chromatogram and the true mol-wt.-distribution function. Three approaches to solve the integral equations are described. The first approach provides a special soln. for the log-normal mol.-wt.-distribution function; the other 2 approaches give 2 numerical solns. for general distribution functions. The use of these solns. in the treatment of gel-permeation-chromatography data is discussed. The present calcns. have the advantage of yielding the true mol.-wt. distribution with relatively few arbitrary assumptions or approxns. A chromatogram of low resolution can be analyzed with equal efficiency. Accurate results are possible with shorter columns and reduced elution time.
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      Gröckner, G. Gradient HPLC of Copolymers and Chromatographic Cross-Fractionation; Springer -Verlag: Berlin, 1992.
      There is no corresponding record for this reference.
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      Pasch H. Analysis of complex polymers by interaction chromatography Adv. Polym. Sci. 1997 128 1 45
      9
      Analysis of complex polymers by interaction chromatography
      Pasch, Harald
      Advances in Polymer Science (1997), 128 (), 1-45CODEN: APSIDK; ISSN:0065-3195. (Springer)
      A review with 101 refs. on the use of interaction chromatog. for analyzing different heterogeneities in complex polymers.
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      Berek D. Coupled liquid chromatographic techniques for the separation of complex polymers Prog. Polym. Sci. 2000 25 873 908
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      Coupled liquid chromatographic techniques for the separation of complex polymers
      Berek, D.
      Progress in Polymer Science (2000), 25 (7), 873-908CODEN: PRPSB8; ISSN:0079-6700. (Elsevier Science Ltd.)
      A review with 108 refs. Size exclusion chromatog. (SEC) dominates the area of mol. characterization of synthetic polymers. Unfortunately, this excellent method can only exceptionally produce simultaneous data on more than one single mol. characteristic of complex polymer systems such as copolymers, polymer blends, or functional polymers, which as rule exhibit a distribution in molar mass, chem. structure, and/or phys. architecture. Further, even single molar mass avs. and distributions detd. by SEC can be considered only semiquant. for complex polymer systems also possessing chem. structure distribution and/or phys. architecture distribution. This is due to the fact that sizes of macromols. in soln. depend on all the above-mentioned mol. characteristics. To solve this problem, alternative liq. chromatog. (LC) procedures must be applied in which (i) the effects of all but one mol. characteristic are suppressed and macromols. are sepd. exclusively according to the remaining characteristic and (ii) the effect of one characteristic is strongly enhanced so that the effects of remaining characteristics can be neglected. In the next stage(s), macromols. can be sepd. according to second (third, etc.) characteristics and we arrive at the two- (three-, or multi-)dimensional liq. chromatog. of complex polymers. Both suppression (i) or enhancement (ii) of LC sepn. selectivity can be reached by a controlled combination of selected sepn. mechanisms such as exclusion, adsorption, partition, soly. (phase sepn.), or ion-effects within one single LC column. The present review describes recent progress in such couplings of sepn. mechanisms.
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      Chang T. Recent Advances in Liquid Chromatography Analysis of Synthetic Polymers Adv. Polym. Sci. 2003 163 1 60
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      Recent advances in liquid chromatography analysis of synthetic polymers
      Chang, Taihyun
      Advances in Polymer Science (2003), 163 (Liquid Chromatography FTIR Microspectroscopy Microwave Assisted Synthesis), 1-60CODEN: APSIDK; ISSN:0065-3195. (Springer-Verlag)
      This review presents recent developments in the anal. of various heterogeneities in synthetic polymers by a variety of liq. chromatog. sepn. as well as detection methods. Synthetic polymers are rarely homogeneous chem. species but have multivariate distributions in mol. wt., chem. compn., chain architecture, functionality, and so on. For a precise characterization of synthetic polymers, all the distributions need to be detd., which is a difficult task, if not impossible. Fortunately in most of the cases it is sufficient to analyze a limited no. of mol. characteristics in order to obtain the information required for a given purpose. Nonetheless, it is still nontrivial if there exists distributions for more than one mol. characteristic. There have been continuing efforts to solve the problem. One approach is to find chromatog. methods sensitive to one mol. characteristic only. In favorable cases, the effect of all but one mol. characteristic can be suppressed to a negligible level. Various interaction chromatog. techniques as well as size exclusion chromatog. are employed for the purpose. Also the multiple detection methods each sensitive to a specific mol. characteristic can provide addnl. information. Various detection methods developed recently such as FT-IR, FT-NMR, and mass spectrometry brought about significant progress in the characterization of complex polymers. This review presents the recent developments in the anal. of various heterogeneities in synthetic polymers by a variety of liq. chromatog. sepn. as well as detection methods.
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      Uliyanchenko E. van der Wal S. Schoenmakers P. J. Challenges in polymer analysis by liquid chromatography Polym. Chem. 2012 3 2313 2335
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      Challenges in polymer analysis by liquid chromatography
      Uliyanchenko, Elena; van der Wal, Sjoerd; Schoenmakers, Peter J.
      Polymer Chemistry (2012), 3 (9), 2313-2335CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
      A review. Synthetic polymers are very important in our daily life. Liq. chromatog. (LC) techniques are very commonly used for mol. characterization of polymers. LC anal. of macromols. is more challenging than anal. of low-mol.-wt. compds. The present review focuses on difficulties assocd. with LC anal. of synthetic polymers. The approaches that allow bringing poorly sol. polymers within the scope of LC are discussed. Different LC modes used for polymer sepns. are reviewed and assocd. practical challenges are identified. Aspects of optimization of sepns. in terms of resoln. (retention factors, selectivity and efficiency) and anal. time are discussed. Modern technologies that may pos. affect the trade-off between speed of anal. and efficiency are considered in this respect. Finally, the issue of detection in LC of polymers is addressed. The advantages and limitations of different detection techniques as well as hyphenated techniques are discussed.
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      Radke W. Polymer separations by liquid interaction chromatography: Principles - prospects - limitations J. Chromatogr. A 2014 1335 62 79
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      Polymer separations by liquid interaction chromatography: Principles - prospects - limitations
      Radke, Wolfgang
      Journal of Chromatography A (2014), 1335 (), 62-79CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
      A review. Most heterogeneities of polymers with respect to different structural features cannot be resolved by only size exclusion chromatog. (SEC), the most frequently applied mode of polymer chromatog. Instead, methods of interaction chromatog. became increasingly important. However, despite the increasing applications the principles and potential of polymer interaction chromatog. are still often unknown to a large no. of polymer scientists. The present review will explain the principles of the different modes of polymer chromatog. Based on selected examples it is shown which sepn. techniques can be successfully applied for sepns. with respect to the different structural features of polymers.
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      Chang T. Lee H. C. Lee W. Park S. Ko C. H. Polymer characterization by temperature gradient interaction chromatography Macromol. Chem. Phys. 1999 200 2188 2204
      14
      Polymer characterization by temperature gradient interaction chromatography
      Chang, Taihyun; Lee, Hee Cheong; Lee, Wonmok; Park, Soojin; Ko, Changhee
      Macromolecular Chemistry and Physics (1999), 200 (10), 2188-2204CODEN: MCHPES; ISSN:1022-1352. (Wiley-VCH Verlag GmbH)
      A review with 45 refs. on the authors' recent results. Thermodn. principles and some applications of the temp. gradient interaction chromatog. (TGIC) recently developed for the characterization of synthetic polymers are described. TGIC is a form of high performance liq. chromatog. (HPLC) that varies column temp. in a programmed manner to control the retention of polymeric species during isocratic elution. The retention of polymers strongly depends on their mol. wts., and the polymers are well sepd. by TGIC in terms of their mol. wts. TGIC is superior to size exclusion chromatog. (SEC) in resoln. and sample loading capacity, and has higher sensitivity to mol. wt. in the anal. of nonlinear polymers. TGIC has an advantage over solvent gradient HPLC because it permits the use of refractive index-sensitive detection method such as differential refractometry and light scattering due to the isocratic elution. In addn., temp. provides finer and more reproducible retention control than the solvent compn., which is important in detg. the mol. wt. distribution by secondary calibration methods. With TGIC anal., the authors found that the mol. wt. distribution of anionically polymd. polymers is much narrower than was generally accepted from SEC anal. The authors also found the TGIC sepn. conditions for polystyrene, polyisoprene, poly(Me methacrylate), poly(vinyl chloride), and poly(vinyl acetate) over wide mol. wt. range. Because of its sensitivity to the mol. wt. alone, TGIC was successfully applied to the characterization of star-shaped polystyrene, and the detailed linking kinetics between living polystyrene anions and a chlorosilane linking agent was investigated.
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      Gorbunov A. A. Skvortsov A. M. Statistical properties of confined macromolecules Adv. Colloid Interface Sci. 1995 62 31 108
      15
      Statistical properties of confined macromolecules
      Gorbunov, Alexei A.; Skvortsov, Alexander M.
      Advances in Colloid and Interface Science (1995), 62 (1), 31-108CODEN: ACISB9; ISSN:0001-8686. (Elsevier)
      A review, with 120 refs. The review presents in a consistent manner the results of a rigorous theory which describes the equil. behavior of an isolated macromol. in a porous medium. An exactly solvable model of a macromol. in a slit-like pore is used as the base model. Various behavioral regimes are analyzed for a macromol. in a pore, realizable at various mol.-to-pore size ratios, as also with varied adsorption interactions. The effect of polymer chain rigidity is discussed, and so is the specific behavior of a macromol. in different forms of pores. Presented also are the results of a rigorous theory for ideal cyclic macromols. in pores under conditions of varied adsorption interactions.Theory is compared with exptl. results on the partition coeffs. of macromols. at no adsorption and with adsorption interactions taking place. Comparing theory with expt. enables detn. of a correlation length of adsorption for various polymer-solvent-adsorbent systems.The basic results are discussed in terms of the sealing theories which account for the excluded vol. effects and for the effect of the thermodn. quality of the solvent upon the behavior of linear and cyclic macromols. in pores.Alongside the discussion on the properties of individual confined macromols., another situation is analyzed: that where a molten amorphous polymer is in contact with solid particles. Various approaches are examd. toward describing such systems. It is suggested and justified that the conformations of flexible-chain macromols. in an amorphous polymer amidst filler particles are identical to the conformations of an isolated chain at the crit. adsorption interaction energy.
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    16. 16
      Skvortsov A. M. Gorbunov A. A. Phase transitions in liquid chromatography of polymers Polym. Sci. U.S.S.R. 1989 31 1307 1313
      There is no corresponding record for this reference.
    17. 17
      Inagaki H. Matsuda H. Kamiyama F. Determination of compositional heterogeneity in copolymers by thin-layer chromatography. I. Preliminary results for styrene-acrylate copolymers Macromolecules 1968 1 520 5
      17
      Determination of compositional heterogeneity in copolymers by thin-layer chromatography. I. Preliminary results for styrene-acrylate copolymers
      Inagaki, Hiroshi; Matsuda, Hisayuki; Kamiyama, Fumio
      Macromolecules (1968), 1 (6), 520-5CODEN: MAMOBX; ISSN:0024-9297.
      The feasibility of detg. the compositional heterogeneity of copolymers by thin-layer chromatog. was demonstrated. Homopolymers and copolymers of styrene and Me acrylate prepd. at various monomer feed ratios were used as test samples. Seven solvents, chosen appropriately from the eluotropic series, were used to develop the chromatograms. No intermediate Rf value was observed, since some species remained immobile while others reached the solvent front. Similar unfavorable results were observed using solvent mixts. Good sepn. was achieved by developing in a concn. gradient, using the system CCl4-MeOAc. By this procedure, the compn. distribution curve of a high-conversion styrene-Me acrylate copolymer was detd. The results agreed well with a calcd. curve based on radical copolymn. kinetics. The limitations of the new technique are discussed briefly. Finally, preliminary data are presented indicating that, under suitable conditions, sepn. of copolymers with respect to differences in steric monomer arrangement is also possible.
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    18. 18
      Belenkii B. G. Gankina E. S. Thin-Layer Chromatography of Polymers Introductory Lecture J. Chromatogr. 1970 53 3 25
      There is no corresponding record for this reference.
    19. 19
      Belenkii B. G. Gankina E. S. Tennikov M. B. Vilenchik L. Z. Fundamental Aspects of Adsorption Chromatography of Polymers and their Experimental Verification by Thin-Layer Chromatography J. Chromatogr. 1978 147 99 110
      19
      Fundamental aspects of adsorption chromatography of polymers and their experimental verification by thin-layer chromatography
      Belen'kii, B. G.; Gankina, E. S.; Tennikov, M. B.; Vilenchik, L. Z.
      Journal of Chromatography (1978), 147 (), 99-110CODEN: JOCRAM; ISSN:0021-9673.
      Math. equations are derived to provide a basis for interpretation of the mechanism of the adsorption chromatog. of polymers; the equations describe the peculiarities of both adsorption chromatog. and mol.-sieve chromatog. The equations were verified exptl. by use of various polystyrene [9003-53-6] samples.
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    20. 20
      Teramachi S. Hasegawa A. Shima Y. Akatsuka M. Nakajima M. Separation of Styrene-Methyl Acrylate Copolymer According to Chemical Composition, Using High-Speed Liquid Chromatography Macromolecules 1979 12 992
      20
      Separation of styrene-methyl acrylate copolymer according to chemical composition, using high-speed liquid chromatography
      Teramachi, Shinya; Hasegawa, Akira; Shima, Yukio; Akatsuka, Makoto; Nakajima, Masahiko
      Macromolecules (1979), 12 (5), 992-6CODEN: MAMOBX; ISSN:0024-9297.
      High-speed liq. chromatog. of a mixt. of Me acrylate-styrene copolymers [25036-19-5] having sharp chem. compn. distributions and different chem. compns. on silica gel columns with micropore size <50 Å by gradient elution with CCl4-MeOAc gave chromatograms having discrete peaks corresponding to the original components. The apparent chem. compn. distribution of components was detd. from the chromatogram by using the resp. components as internal stds., and compared with that calcd. from copolymn. kinetics. The distribution obtained on a high-efficiency column was in fairly good agreement with the theor. distribution. The mol. sieve effect in the columns used was negligible.
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    21. 21
      Armstrong D. W. Bui K. H. Nonaqueous Reversed-Phase Liquid Chromatographic Fractionation of Polystyrene Anal. Chem. 1982 54 706 708
      21
      Nonaqueous reversed-phase liquid chromatographic fractionation of polystyrene
      Armstrong, Daniel W.; Bui, K. H.
      Analytical Chemistry (1982), 54 (4), 706-8CODEN: ANCHAM; ISSN:0003-2700.
      A binary solvent mobile phase (i.e., CH2Cl2 and MeOH) in conjunction with reversed-phase thin-layer chromatog. (TLC) or high-performance liq. chromatog. (HPLC) can be used to fractionate polystyrene [9003-53-6]. Sepn. times are ∼15 min and the resoln. is better than comparable mol. sieve or TLC methods. Sepn. of polymers with mol. wts. ≤107 posed no problems for this technique. The TLC fractionation of polystyrene occurs as a result of the change in mobile phase compn. along the length of the chromatogram. This is verified by gradient reversed-phase HPLC expts. and by direct anal. of the mobile phase impregnating the developed TLC plates.
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    22. 22
      Lee H. C. Chang T. Polymer Molecular Weight Characterization By Temperature Gradient High Performance Liquid Chromatography Polymer 1996 37 5747 5749
      22
      Polymer molecular weight characterization by temperature gradient high performance liquid chromatography
      Lee, Hee Cheong; Chang, Taihyun
      Polymer (1996), 37 (25), 5747-5749CODEN: POLMAG; ISSN:0032-3861. (Elsevier)
      We report a novel method of temp. gradient interaction HPLC for the characterization of mol. wt. distribution of macromols. A very fine and reproducible control of interaction between polymer chains and the packing material can be achieved by altering the column temp. A mixt. of 10 polystyrene samples (mol. wt. range: 1700-2,890,000) of narrow mol. wt. distribution are analyzed by this method. Near complete sepn. down to the baseline is achieved with the use of a single C18 bonded silica column. This method is thus proven to provide a much superior resoln. to the conventional size-exclusion chromatog.
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    23. 23
      Lee W. Lee H. Cha J. Chang T. Hanley K. J. Lodge T. P. Molecular weight distribution of polystyrene made by anionic polymerization Macromolecules 2000 33 5111 5115
      23
      Molecular weight distribution of polystyrene made by anionic polymerization
      Lee, Wonmok; Lee, Hyunjung; Cha, Junhoe; Chang, Taihyun; Hanley, Kenneth J.; Lodge, Timothy P.
      Macromolecules (2000), 33 (14), 5111-5115CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      A set of polystyrenes of varying mol. wts. was synthesized by anionic polymn. under identical conditions, and the mol. wt. distributions were critically examd. Polymn. of styrene was initiated with 2-butyllithium in cyclohexane at 45 °C. During the polymn., seven aliquots of the reaction mixt. were taken out at various reaction times using a cannula and terminated. The polymn. time varying mol. wts. and mol. wt. distributions of the polystyrenes were analyzed by temp. gradient interaction chromatog. (TGIC) as well as size exclusion chromatog. The mol. wt. distribution of the polystyrene approaches the Poisson distribution in the late stages of the polymn., in accordance with the early prediction of Flory. We also confirmed that the mol. wt. distribution of polystyrenes detd. by TGIC is close to the true value.
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    24. 24
      Chang T. Lee W. Lee H. C. Cho D. Park S. Polymer characterization by non-size exclusion chromatography: Temperature gradient interaction chromatography Am. Lab. 2002 34 39
      24
      Polymer characterization by non-size exclusion chromatography: temperature gradient interaction chromatography
      Chang, Taihyun; Lee, Wonmok; Lee, Hee Cheong; Cho, Donghyun; Park, Soojin
      American Laboratory (Shelton, CT, United States) (2002), 34 (14), 39-41CODEN: ALBYBL; ISSN:0044-7749. (International Scientific Communications, Inc.)
      Temp. gradient interaction chromatog. (TGIC) was used to characterize the mol. wt. distribution of various linear polystyrene (PS) stds. using a reversed-phase silica column. The temp. of the sepn. column is varied in a programmed way during elution to control the enthalpic interaction of polymeric solutes with the stationary phase. The app. for TGIC is a typical high performance liq. chromatog. instrument with modification to precisely control the temp. of the column and the mobile phase. Due to the high sensitivity to functional groups, two PS with identical MW except for a single hydroxyl end group difference were resolved. The MW sensitivity of TGIC also provides high resoln. in the anal. of branched polymers. TGIC also demonstrates a loading capacity much higher than SEC, which could be used to prep. extra high-quality primary and/or secondary std. polymers on a lab. scale.
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    25. 25
      Martin A. J. P. Biochim. Soc. Symp. 1949 3 4
      There is no corresponding record for this reference.
    26. 26
      Klumperman B. Cools P. Philipsen H. Staal W. A qualitative study to the influence of molar mass on retention in gradient polymer elution chromatography Macromol. Symp. 1996 110 1 13
      There is no corresponding record for this reference.
    27. 27
      Berek D. Liquid adsorption chromatography of copolymers: Molar mass (In)dependent retention Macromolecules 1999 32 3671 3673
      27
      Liquid Adsorption Chromatography of Copolymers: Molar Mass (In)dependent Retention
      Berek, D.
      Macromolecules (1999), 32 (11), 3671-3673CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Liq. adsorption chromatog. with a continuous solvent gradient elution has been shown by several authors to often sep. random and graft copolymers according to their chem. compn. whereas their molar masses do not play an important role. A tentative explanation of this finding is presented. It is assumed that the copolymer species travel along the column with a velocity which exactly corresponds with that of the eluent compn., exhibiting a displacing power just necessary to prevent a fast progress of the macromols. due to their exclusion. Under specific circumstances, retention of macromols. at this adsorption promoting "barrier" depends almost exclusively on the copolymer compn. and not on its molar mass. This hypothesis is based on the mechanism of the recently proposed and tested liq. chromatog. elution of homopolymers under limiting conditions of desorption and takes into account the simultaneous effect of adsorption and exclusion of macromols. onto/from the column packing.
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    28. 28
      Brun Y. The mechanism of copolymer retention in interactive polymer chromatography. I. Critical point of adsorption for statistical copolymers J. Liq. Chromatogr. Relat. Technol. 1999 22 3027 3065
      28
      The mechanism of copolymer retention in interactive polymer chromatography. I. Critical point of adsorption for statistical copolymers
      Brun, Y.
      Journal of Liquid Chromatography & Related Technologies (1999), 22 (20), 3027-3065CODEN: JLCTFC; ISSN:1082-6076. (Marcel Dekker, Inc.)
      A comprehensive anal. of interactive polymer chromatog. is presented. Isocratic liq. chromatog. of polymers at the crit. eluent compn. (the transition point where size-exclusion and adsorption interactions completely compensate each other) is currently used to sep. functional oligomers and block copolymers. We have extended the concept of this crit. elution chromatog. to the cases of statistical copolymers as well as porous stationary phases with heterogeneous surfaces (viz., surfaces with both inert and active groups). The theory provides the quant. condition for statistical copolymer chains to have a single adsorption-desorption transition point. The random copolymers with narrow chem. compn. distribution (CCD) always posses such a point. For non-random copolymers this condition includes the comparison between the mean length of chain segments connecting the attractive walls of the pore and the chem. correlation segment characterizing the randomness of the copolymer microstructure or the surface of this pore. If the crit. transition point exists, then the copolymer chains behave as hypothetical homopolymer chains with a single energy of interaction between the effective monomer units and the active groups at the surface. The relationship between this energy and the microstructure of copolymer chains has been also analyzed. If copolymer has a broad CCD, each compositionally homogeneous fraction has its own adsorption-desorption threshold. The partial transition points have been established for the copolymers with blocky or alternating microstructure. Only a portion of the copolymer chain effectively behaves as a homopolymer chain at these points. This property was used in the past for the sepn. of block copolymers according to the length of blocks comprised of the monomer units of a specific type.
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    29. 29
      Brun Y. The mechanism of copolymer retention in interactive polymer chromatography. II. Gradient separation J. Liq. Chromatogr. Relat. Technol. 1999 22 3067 3090
      29
      The mechanism of copolymer retention in interactive polymer chromatography. II. Gradient separation
      Brun, Y.
      Journal of Liquid Chromatography & Related Technologies (1999), 22 (20), 3067-3090CODEN: JLCTFC; ISSN:1082-6076. (Marcel Dekker, Inc.)
      The mol.-statistical theory of polymer solns. in confined media is applied to the conventional chromatog. theory of gradient elution. This approach leads to the prediction of the special mode of interactive polymer chromatog.: gradient elution at crit. point of adsorption. We demonstrate theor. and exptl. that under appropriate conditions elution of each compositionally homogeneous fraction of copolymer occurs at the crit. mobile phase compn. This crit. mobile phase compn. depends only on the local structure of the copolymer chain and is independent of its mol. wt. As a consequence, gradient elution produces the chem. compn. distribution of the copolymer. The theory provides the quant. conditions for statistical copolymer chains to have a single transition point. Equations describing relationships between the crit. eluent compn. and the chem. compn. and microstructure of macromols. are developed. The exptl. verification of the theory was performed by the normal phase isocratic and gradient elution of chlorinated polyethylene with various chem. compns. (chlorine content) and mol. wts. To the best of our knowledge, these expts., for the first time, demonstrate the existence of the adsorption-desorption transition point for statistical copolymers. The gradient sepn. at the crit. point of adsorption can be applied also to other complex polymers contg. various types of mol. heterogeneity.
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    30. 30
      Bashir M. A. Radke W. Predicting the chromatographic retention of polymers: Application of the polymer model to poly(styrene/ethylacrylate) copolymers J. Chromatogr. A 2012 1225 107 112
      30
      Predicting the chromatographic retention of polymers: Application of the polymer model to poly(styrene/ethylacrylate)copolymers
      Bashir, Mubasher A.; Radke, Wolfgang
      Journal of Chromatography A (2012), 1225 (), 107-112CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
      The retention behavior of a range of statistical poly(styrene/ethylacrylate) copolymers is investigated, in order to det. the possibility to predict retention vols. of these copolymers based on a suitable chromatog. retention model. It was found that the compn. of elution in gradient chromatog. of the copolymers is closely related to the eluent compn. at which, in isocratic chromatog., the transition from elution in adsorption to exclusion mode occurs. For homopolymers this transition takes place at a crit. eluent compn. at which the molar mass dependence of elution vol. vanishes. Thus, similar crit. eluent compns. can be defined for statistical copolymers. The existence of a crit. eluent compn. is further supported by the narrower peak width, indicating that the broad molar mass distribution of the samples does not contribute to the retention vol. It is shown that the existing retention model for homopolymers allows for correct quant. predictions of retention vols. based on only three appropriate initial expts. The selection of these initial expts. involves a gradient run and two isocratic expts., one at the compn. of elution calcd. from first gradient run and second at a slightly higher eluent strength.
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    31. 31
      Ryu J. Chang T. Thermodynamic prediction of polymer retention in temperature-programmed HPLC Anal. Chem. 2005 77 6347 6352
      31
      Thermodynamic Prediction of Polymer Retention in Temperature-Programmed HPLC
      Ryu, Jinsook; Chang, Taihyun
      Analytical Chemistry (2005), 77 (19), 6347-6352CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
      The polymer retention behavior in temp. gradient interaction chromatog. is investigated based on thermodn. consideration of the retention factor. The polymer retention predicted by the model calcn. is in good agreement with the exptl. results, and the model allows devising a temp. program for designed retention behaviors such as a linear dependence of retention vol. on log(mol. wt.) of polymers. In addn., the migration behavior of polymeric solute along the sepn. column can be simulated, which shows strong mol. wt. dependence. The migration behavior is also confirmed exptl. by employing different length columns or delayed injection.
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    32. 32
      Chang T. Polymer characterization by interaction chromatography J. Polym. Sci., Part B: Polym. Phys. 2005 43 1591 1607
      32
      Polymer characterization by interaction chromatography
      Chang, Taihyun
      Journal of Polymer Science, Part B: Polymer Physics (2005), 43 (13), 1591-1607CODEN: JPBPEM; ISSN:0887-6266. (John Wiley & Sons, Inc.)
      A review. Liq. chromatog. (LC) is a powerful tool for the characterization of synthetic polymers, that are inherently heterogeneous in mol. wt., chain architecture, chem. compn., and microstructure. Of different versions of the LC methods, size exclusion chromatog. (SEC) is most commonly used for the mol. wt. distribution anal. SEC separates the polymer mols. according to the size of a polymer chain, a well-defined function of mol. wt. for linear homopolymers. The same, however, cannot be said of nonlinear polymers or copolymers. Hence, SEC is ill suited for and inefficient in sepg. the mols. in terms of chem. heterogeneity, such as differences in chem. compn. of copolymers, tacticity, and functionality. For these purposes, another chromatog. method called interaction chromatog. (IC) is found as a better tool because its sepn. mechanism is sensitive to the chem. nature of the mols. The IC sepn. utilizes the enthalpic interactions to vary adsorption or partition of solute mols. to the stationary phase. Thus, it is used to sep. polymers in terms of their chem. compn. distribution or functionality. Further, the IC method has been shown to give rise to much higher resoln. over SEC in sepg. polymers by mol. wt. We present here our recent progress in polymer characterization with this method.
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    33. 33
      Lochmüller C. H. Moebus M. A. Liu Q. C. Jiang C. Elomaa M. Temperature Effect On Retention and Separation of Poly(Ethylene Glycol)S in Reversed-Phase Liquid Chromatography J. Chromatogr. Sci. 1996 34 69 76
      There is no corresponding record for this reference.
    34. 34
      Teramachi S. Matsumoto H. Kawai T. Direction of temperature gradient for normal-phase temperature gradient interaction chromatography in polystyrene fractionation J. Chromatogr. A 2005 1100 40 44
      34
      Direction of temperature gradient for normal-phase temperature gradient interaction chromatography in polystyrene fractionation
      Teramachi, Shinya; Matsumoto, Hiroshi; Kawai, Tadatomo
      Journal of Chromatography A (2005), 1100 (1), 40-44CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
      Temp. gradient interaction chromatog. (TGIC) is a powerful technique for mol. wt. fractionation of polymers, in which the interaction strength is controlled by varying the column temp. In the present paper, the effects of the sign of the temp. dependence of the retention and the direction of the temp. gradient (raising or lowering) on TGIC in the normal-phase mode were studied for the mol. wt. fractionation of polystyrene samples in org. mobile phases. It was found that a pos. temp. gradient was effective in the system consisting of amino-modified silica (NH2) column and the eluent mixt. of THF and n-hexane where retention decreased with increasing temp. A neg. temp. gradient was effective for the systems consisting of a bare-silica column//chloroform/n-hexane and NH2-column//chloroform/n-hexane, where retention increased with increasing temp. Increasing retention with increasing temp. has been found, so far, only for a water-sol. polymer (PEO) in an aq. mobile phase in RP-TGIC.
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    35. 35
      Matsumoto H. Kawai T. Teramachi S. Direction of temperature gradient and retention mechanism in normal-phase temperature gradient interaction chromatography for poly(methyl methacrylate) fractionation Polym. J. 2007 39 458 463
      35
      Direction of temperature gradient and retention mechanism in normal-phase temperature gradient interaction chromatography for poly(methyl methacrylate) fractionation
      Matsumoto, Hiroshi; Kawai, Tadatomo; Teramachi, Shinya
      Polymer Journal (Tokyo, Japan) (2007), 39 (5), 458-463CODEN: POLJB8; ISSN:0032-3896. (Society of Polymer Science, Japan)
      Temp. gradient interaction chromatog. (TGIC) is a powerful technique for mol. characterization of polymers, in which the interaction strength is controlled by varying the column temp. In the present paper, the direction of temp. gradient for normal-phase mode TGIC in poly(Me methacrylate) (PMMA) fractionation was studied by using System I (column: cyano-modified silica // eluent: 1,4-dioxane/n-hexane) and System II (bare silica // 1,4-dioxane/CH2Cl2), resp. It was found that PMMA samples were sepd. by pos. and neg. temp. gradients using the resp. systems. The results were also discussed theor.
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    36. 36
      Cho D. Park S. Hong J. Chang T. Retention mechanism of poly(ethylene oxide) in reversed-phase and normal-phase liquid chromatography J. Chromatogr. A 2003 986 191 198
      36
      Retention mechanism of poly(ethylene oxide) in reversed-phase and normal-phase liquid chromatography
      Cho, Donghyun; Park, Soojin; Hong, Jeongmin; Chang, Taihyun
      Journal of Chromatography, A (2003), 986 (2), 191-198CODEN: JCRAEY; ISSN:0021-9673. (Elsevier Science B.V.)
      The retention behavior of low- and high-mol.-mass poly(ethylene oxide) (PEO) in reversed-phase (RP) and normal-phase (NP) liq. chromatog. was investigated. In RPLC using a C18 bonded silica stationary phase and an acetonitrile-water mixt. mobile phase, the sorption process of PEO to the stationary phase showed ΔH°>0 and ΔS°>0. Therefore, PEO retention in RPLC sepn. is an energetically unfavorable, entropy-driven process, which results in an increase of PEO retention as the temp. increases. In addn., at the enthalpy-entropy compensation point the elution vol. of PEO was very different from the column void vol. These observations are quite different from the RPLC retention behavior of many org. polymers. The peculiar retention behavior of PEO in RPLC sepn. can be understood in terms of the hydrophobic interaction of this class of typical amphiphilic compds. with the non-polar stationary phase, on the one hand, and with the aq. mobile phase, on the other. The entropy gain due to the release of the solvated water mols. from the PEO chain and the stationary phase is believed to be responsible for the entropy-driven sepn. process. On the other hand, in NPLC using an amino-bonded silica stationary phase and an acetonitrile-water mixt. mobile phase, PEO showed normal enthalpy-driven retention behavior: ΔH°<0 and ΔS°<0, with the retention decreasing with increasing temp. and PEO eluting near the column void vol. at the enthalpy-entropy compensation point. Therefore, high-resoln. temp. gradient NPLC sepn. of high-mol.-mass PEO samples can be achieved with relative ease. The mol. mass distribution of high-mol.-mass PEO was found to be much narrower than that measured by size-exclusion chromatog.
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    37. 37
      Cong R. J. deGroot W. Parrott A. Yau W. Hazlitt L. Brown R. Miller M. Zhou Z. A New Technique for Characterizing Comonomer Distribution in Polyolefins: High-Temperature Thermal Gradient Interaction Chromatography (HT-TGIC) Macromolecules 2011 44 3062 3072
      37
      A new technique for characterizing comonomer distribution in polyolefins: high-temperature thermal gradient interaction chromatography (HT-TGIC)
      Cong, Rongjuan; de Groot, Willem; Parrott, Al; Yau, Wallace; Hazlitt, Lonnie; Brown, Ray; Miller, Matt; Zhou, Zhe
      Macromolecules (Washington, DC, United States) (2011), 44 (8), 3062-3072CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      This paper documents a new polyolefin characterization technique, high-temp. thermal gradient interaction chromatog. (HT-TGIC or TGIC), to quantify comonomer distribution. A set of homogeneous ethylene-octene homopolymers are used with a com. available column having a graphitic substrate (HYPERCARB) to demonstrate this technique's applicability to fractionating polyolefins. The sepn. mechanism appears to be based on the interaction of the polyolefin chains with the graphite surface upon a temp. change in an isocratic solvent. The TGIC technique overcomes the key issues encountered in crystn. based techniques and in high-temp. liq. chromatog. with a solvent gradient (HT-LC). Crystn. based techniques cover only a narrow anal. range of 0-9 mol % comonomer content and suffer from potential error in the anal. caused by cocrystn. effects. HT-LC is limited in its capability because of the limited choice in detectors available. Conversely, TGIC, because of the simplicity in solvent compn., has many com. available detectors, such as IR detectors (IR), light scattering detectors (LS), and viscometer detectors. For example, a triple detector TGIC with online IR, LS, and viscometer not only is capable of providing comonomer content and distribution from its TGIC retention temp. profile but also can provide a comprehensive microstructure mapping of mol. wt. (MW) and intrinsic viscosity (IV) across the comonomer distribution. Under the exptl. conditions used in this study, all these features can be obtained in a short anal. time of less than 1 h, for a comonomer content range of from 0 to 50 mol %. Addnl., TGIC is not subject to the cocrystn. problems that traditional polyolefins comonomer distribution characterization techniques have.
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    38. 38
      Lee H. C. Chang T. Characterization of Binary Polymer Mixtures by Simultaneous Size-Exclusion Chromatography and Interaction Chromatography Macromolecules 1996 29 7294 7296
      38
      Characterization of Binary Polymer Mixtures by Simultaneous Size Exclusion Chromatography and Interaction Chromatography
      Lee, Hee Cheong; Chang, Taihyun
      Macromolecules (1996), 29 (22), 7294-7296CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      We report a novel method to characterize binary polymer mixts. In this method, one component of a polymer mixt. is sepd. by a size exclusion mechanism and the other by an interactive mechanism simultaneously under single isocratic elution. For the effective sepn. by an interactive mechanism, the interaction strength between polymer chains and the packing material is controlled by programming the column temp. Using a series of three C18 bonded silica columns with different pore size and CH2Cl2/CH3CN mixt. as the mobile phase, we can sep. 10 polystyrene and 5 poly(Me methacrylate) stds. simultaneously in the interaction and the size exclusion region, resp. Resoln. of the method is found to be satisfactory.
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    39. 39
      Park S. Park I. Chang T. Ryu C. Y. Interaction-controlled HPLC for block copolymer analysis and separation J. Amer. Chem. Soc. 2004 126 8906 8907
      39
      Interaction-Controlled HPLC for Block Copolymer Analysis and Separation
      Park, Soojin; Park, Insun; Chang, Taihyun; Ryu, Chang Y.
      Journal of the American Chemical Society (2004), 126 (29), 8906-8907CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      An interaction-controlled HPLC technique was developed to analyze homopolymer precursors in block copolymer systems that are not easily identified by size exclusion chromatog. (SEC) and to obtain block copolymers that are homopolymer-free and compositionally narrower than the as-synthesized ones. We demonstrate that a "single peak" in SEC does not necessarily mean that the block copolymers are free of homopolymers (due to limitations in the SEC anal. of block copolymers) and propose to employ the interaction-controlled HPLC strategy for rigorous anal. and purifn. of block copolymers in terms of their chem. heterogeneity.
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    40. 40
      Park S. Cho D. Ryu J. Kwon K. Lee W. Chang T. Fractionation of block copolymers prepared by anionic polymerization into fractions exhibiting three different morphologies Macromolecules 2002 35 5974 5979
      40
      Fractionation of Individual Blocks of Block Copolymers Prepared by Anionic Polymerization into Fractions Exhibiting Three Different Morphologies
      Park, Soojin; Cho, Donghyun; Ryu, Jinsook; Kwon, Kyoon; Lee, Wonmok; Chang, Taihyun
      Macromolecules (2002), 35 (15), 5974-5979CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      In this study we fractionated a polystyrene-block-polyisoprene diblock copolymers (PS-b-PI) prepd. by anionic polymn. into fractions which have a narrower distribution in mol. wt. and in chem. compn. The strategy was to use two-dimensional HPLC: reversed phase HPLC to fractionate PI block and normal phase HPLC to fractionate PS block with a minimal effect of the other block. The working principle of the sepn. method was confirmed for a low mol. wt. PS-b-PI (2.4 kg/mol). With the aid of matrix assisted laser desorption/ionization mass spectrometry, we found that the sepn. method could resolve each mer of the PS-b-PI. We extended the application to a high mol. wt. diblock copolymer (24 kg/mol) and established the method as a promising tool to further fractionate block copolymers into mol. species better defined in mol. wt. and in compn. We obsd. a significant variation in av. mol. wt. and in compn. of the fractionated samples. These variations were large enough to show different morphologies for the fractions taken from the same mother block copolymer.
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    41. 41
      Chung B. H. Park S. Chang T. HPLC fractionation and surface micellization behavior of polystyrene-b-poly(methyl methacrylate) Macromolecules 2005 38 6122 6127
      41
      HPLC Fractionation and Surface Micellization Behavior of Polystyrene-b-poly(methyl methacrylate)
      Chung, Bonghoon; Park, Soojin; Chang, Taihyun
      Macromolecules (2005), 38 (14), 6122-6127CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      A polystyrene-block-poly(Me methacrylate) (PS-b-PMMA) was fractionated by HPLC, and the morphol. of surface micelles formed at the air/water interface was studied. Individual PS and PMMA blocks were fractionated by normal-phase and reversed-phase HPLC, resp., into three fractions each to obtain nine fractions of narrower distribution in mol. wt. and in compn. Although the mother PS-b-PMMA was prepd. by anionic polymn. and had a narrow mol. wt. distribution as characterized by size exclusion chromatog. (mol. wt. = 72.8 kg/mol, mol. wt./Mn = 1.08, PS% = 73.7%), the nine fractionated samples showed significant variations in mol. wt. (Mw = 63.1-79.5 kg/mol) and in compn. (PS% = 66.5-76.3%). The fractionated block copolymers formed more uniform surface micelles than the unfractionated mother PS-b-PMMA and exhibited a large variation with respect to the compn. The PS-b-PMMA fraction of the lowest PS content (66.5%) showed spherical micelles only. Rod-shaped micelles started to appear with a slight increase in the PS content, but circular and rod-shaped micelles coexist over ca. 10% concn. range and no sharp phase boundary appears to exist. The rod-shaped micelles formed at low PS contents exhibit a structure of linearly connected circular micelles.
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    42. 42
      Lee H. C. Lee W. Chang T. Yoon J. S. Frater D. J. Mays J. W. Linking-reaction kinetics of star shaped polystyrene by temperature gradient interaction chromatography Macromolecules 1998 31 4114 4119
      42
      Linking Reaction Kinetics of Star Shaped Polystyrene by Temperature Gradient Interaction Chromatography
      Lee, Hee Cheong; Lee, Wonmok; Chang, Taihyun; Yoon, Jin San; Frater, Donna J.; Mays, Jimmy W.
      Macromolecules (1998), 31 (13), 4114-4119CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      The linking reaction kinetics of a chlorosilane-linked polystyrene six-arm star was investigated by temp. gradient interaction chromatog. using a light scattering detector. The precursor arm material (Mw = 83,000) was made by anionic polymn. and end capped with isoprene, and 1,2-bis(trichlorosilyl)ethane was used as the linking agent. All the reaction intermediates, from unlinked arm to six-arm star, were successfully resolved from the aliquots taken from the reactor at various linking reaction times. From the time-varying relative abundance of the star mols. with different nos. of arms, linking reaction rate consts. were detd. The linking reaction rate becomes progressively slower as the no. of attached arms increases. We were able to ext. the quant. ratio of the linking rate consts., k5/k4 = 0.097 and k6/k5 = 0.30, where ki stands for the rate const. of the reaction incorporating the ith arm to an (i - 1)-arm star to form an i arm star. The larger value of k6/k5 than k5/k4 can be interpreted from the mol. structures of the linking agent and polymeric anions.
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    43. 43
      Ahn S. Lee H. Lee S. Chang T. Characterization of Branched Polymers by Comprehensive Two-Dimensional Liquid Chromatography with Triple Detection Macromolecules 2012 45 3550 3556
      43
      Characterization of Branched Polymers by Comprehensive Two-Dimensional Liquid Chromatography with Triple Detection
      Ahn, Seonyoung; Lee, Hyojoon; Lee, Sekyung; Chang, Taihyun
      Macromolecules (Washington, DC, United States) (2012), 45 (8), 3550-3556CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      In the branching anal. by size exclusion chromatog. (SEC)/triple detection (concn., light scattering, and viscosity detectors) method, the branch no. is calcd. from the extent of chain size contraction due to chain branching relative to the linear polymer of the same mol. wt. (MW). A problem can arise from the fact that polymer chain size depends on both MW and chain branching. Since SEC separates polymers according to the chain size, an SEC fraction of randomly branched polymers may contain polymer species heterogeneous in both MW and chain architecture in general. As a soln. of the problem, we propose a sepn. of polymers by interaction chromatog. according to MW first and then measure the chain size distribution of polymers in the homogeneous MW fraction by SEC/triple detection. The anal. scheme is successfully established by online two-dimensional liq. chromatog. combining temp. gradient interaction chromatog. and SEC/triple detection.
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    44. 44
      Cho D. Park S. Chang T. Ute K. Fukuda I. Kitayama T. Temperature gradient interaction chromatography and MALDI-TOF mass spectrometry analysis of stereoregular poly(ethyl methacrylate)s Anal. Chem. 2002 74 1928 1931
      44
      Temperature gradient interaction chromatography and MALDI-TOF mass spectrometry analysis of stereoregular poly(ethyl methacrylate)s
      Cho, Donghyun; Park, Soojin; Chang, Taihyun; Ute, Koichi; Fukuda, Iichiro; Kitayama, Tatsuki
      Analytical Chemistry (2002), 74 (8), 1928-1931CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
      Temp. gradient interaction chromatog. (TGIC) was applied for the sepn. of stereoregular poly(Et methacrylate) (PEMA) according to the tacticity. Three PEMA samples with differing tacticity (rr triad content: 0, 53, and 91%) prepd. by anionic polymn. were used. C18 bonded silica and a mixt. of CH2Cl2 and MeCN (30/70, vol./vol.) were used as stationary and mobile phase, resp. TGIC was able to sep. the PEMA samples, showing the increasing retention in the order of decreasing rr triad contents; however TGIC elution peaks of the three PEMAs were not fully resolved but, rather, were partially overlapped. To isolate the tacticity effect from the mol. wt. effect on the TGIC retention, the PEMA samples were fractionated by TGIC, and the accurate mol. wt. of the fractions was detd. by MALDI-TOF mass spectrometry. The fractions showed a much narrower mol. wt. distribution than the mother PEMAs. The TGIC fractions of similar mol. wt. but with different tacticity were fully resolved by TGIC, but mother PEMAs were not. These results indicate that the retention in TGIC is affected by both tacticity and mol. wt.
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    45. 45
      Perny S. Allgaier J. Cho D. Lee W. Chang T. Synthesis and Structural Analysis of an H-Shaped Polybutadiene Macromolecules 2001 34 5408 5415
      45
      Synthesis and Structural Analysis of an H-Shaped Polybutadiene
      Perny, Sebastien; Allgaier, Juergen; Cho, Donghyun; Lee, Wonmok; Chang, Taihyun
      Macromolecules (2001), 34 (16), 5408-5415CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      The synthesis of an H-shaped polybutadiene homopolymer as well as its detailed structural characterization is investigated. Anionic polymn. techniques together with chlorosilane linking agents were used for the prodn. of the material. After each reaction step samples were taken and analyzed by size exclusion chromatog. (SEC), membrane osmometry (MO), NMR, and temp. gradient interaction chromatog. (TGIC). According to the characterization by SEC, MO, and NMR, the H-polymer showed a high degree of structural uniformity after purifn. by fractionation, and no significant amts. of differently branched byproducts could be detected. The TGIC anal. however revealed the presence of large amts. of structures, mainly with lower branching degree. We also found that a significant isotope effect exists in the TGIC retention between deuterated and hydrogenous polymers. In our case, where the H-polymer is partially deuterated, the TGIC anal. enabled us to resolve all the side products. Comparison of the different anal. methods indicates that the precise structural anal. of branched model polymers such as the H-polymer requires more sophisticated methods than used in the past.
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    46. 46
      Ahn S. Im K. Chang T. Chambon P. Fernyhough C. M. 2D-LC Characterization of Comb-Shaped Polymers Using Isotope Effect Anal. Chem. 2011 83 4237 4242
      46
      2D-LC Characterization of Comb-Shaped Polymers Using Isotope Effect
      Ahn, Seonyoung; Im, Kyuhyun; Chang, Taihyun; Chambon, Pierre; Fernyhough, Christine M.
      Analytical Chemistry (Washington, DC, United States) (2011), 83 (11), 4237-4242CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
      A rigorous mol. characterization of comb-shaped polystyrene (PS) was carried out taking advantage of its mol. structure, a normal hydrogenous backbone, and deuterated side chains. Normal phase LC (NPLC) can sep. the comb PS species well according to their mol. wt. Nonetheless, it cannot distinguish the backbone from the side chains and the differently structured polymers having a similar mol. wt., e.g, a single backbone comb and a coupled backbone comb with fewer side chains. In contrast to NPLC, the hydrogenous polymer is retained longer than the deuterated counterpart in reversed phase LC (RPLC). When the isotope sensitivity of RPLC is taken advantage of, the comb PS is cross fractionated by NPLC and RPLC, and a two-dimensional mapping with respect to the backbone chain length and the no. of branches is fully established.
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    47. 47
      Berek D. Liquid chromatography of macromolecules under limiting conditions of desorption. 1. Principles of the method Macromolecules 1998 31 8517 8521
      47
      Liquid Chromatography of Macromolecules under Limiting Conditions of Desorption. 1. Principles of the Method
      Berek, D.
      Macromolecules (1998), 31 (24), 8517-8521CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      The liq. chromatog. of macromols. under limiting conditions of desorption (LC LCD) is based on a combination of exclusion and adsorption sepn. mechanisms. Eluent promotes desorption of macromols. that are dissolved in an adsorption-promoting liq. and injected into a liq. chromatog. (LC) column packed with porous adsorptive packing. The zone of sample solvent forms an "adsorption promoting barrier". Under properly chosen, "limiting", conditions the transport of adsorbing polymer species along the column is slowed since they cannot pass the above adsorption-promoting barrier. As result, macromols. of various sizes and molar masses leave LC column in the form of a rather narrow band immediately behind the zone of their initial solvent. At the same time, other kinds of polymer chains which exhibit lower affinity toward column packing and less adsorption surmount the zone of their original solvent. They are eluted in the size exclusion chromatog. mode. In this way macromols. with different chem. structures can be discriminated. The LC LCD idea has been tested with a model system comprising poly(Me methacrylate) probes, silica gel column packing, toluene (adsorbing liq.), and THF (desorbing liq.). Some applications of this novel LC procedure have been proposed. Include sepn. of two-component and multicomponent blends, various kinds of copolymers, and oligomers.
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    48. 48
      Rollet M. Pelletier B. Berek D. Maria S. Phan T. N. T. Gigmes D. Separation of parent homopolymers from polystyrene and poly(ethylene oxide) based block copolymers by liquid chromatography under limiting conditions of desorption-3. Study of barrier efficiency according to block copolymers’ chemical composition J. Chromatogr. A 2016 1462 63 72
      48
      Separation of parent homopolymers from polystyrene and poly(ethylene oxide) based block copolymers by Liquid Chromatography under Limiting Conditions of Desorption-3. Study of barrier efficiency according to block copolymers' chemical composition
      Rollet, Marion; Pelletier, Berengere; Berek, Dusan; Maria, Sebastien; Phan, Trang N. T.; Gigmes, Didier
      Journal of Chromatography A (2016), 1462 (), 63-72CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
      Liq. Chromatog. under Limiting Conditions of Desorption (LC LCD) is a powerful sepn. tool for multicomponent polymer systems. This technique is based on a barrier effect of an appropriate solvent, which is injected in front of the sample, and which decelerates the elution of selected macromols. In this study, the barrier effects have been evaluated for triblock copolymers polystyrene-b-poly(ethylene oxide)-b-polystyrene (PS-b-PEO-b-PS) according to the content of polystyrene (wt% PS) and PEO-block molar mass. PS-b-PEO-b-PS samples were prepd. by Atom Transfer Radical Polymn. (ATRP). The presence of resp. parent homopolymers was investigated by applying optimized LC LCD conditions. It was found that the barrier compn. largely affects the efficiency of sepn. and it ought to be adjusted for particular compn. range of block copolymers.
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    49. 49
      Chatterjee T. Rickard M. A. Pearce E. Pangburn T. O. Li Y. F. Lyons J. W. Cong R. J. deGroot A. W. Meunier D. M. Separating effective high density polyethylene segments from olefin block copolymers using high temperature liquid chromatography with a preloaded discrete adsorption promoting solvent barrier J. Chromatogr. A 2016 1465 107 116
      49
      Separating effective high density polyethylene segments from olefin block copolymers using high temperature liquid chromatography with a preloaded discrete adsorption promoting solvent barrier
      Chatterjee, Tirtha; Rickard, Mark A.; Pearce, Eric; Pangburn, Todd O.; Li, Yongfu; Lyons, John W.; Cong, Rongjuan; deGroot, A. Willem; Meunier, David M.
      Journal of Chromatography A (2016), 1465 (), 107-116CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
      Recent advances in catalyst technol. have enabled the synthesis of olefin block copolymers (OBC). One type is a "hard-soft" OBC with a high d. polyethylene (HDPE) block and a relatively low d. polyethylene (VLDPE) block targeted as thermoplastic elastomers. Presently, one of the major challenges is to fractionate HDPE segments from the other components in an exptl. OBC sample (block copolymers and VLDPE segments). Interactive high temp. liq. chromatog. (HTLC) is ineffective for OBC sepn. as the HDPE segments and block copolymer chains experience nearly identical enthalpic interactions with the stationary phase and co-elute. In this work we have overcome this challenge by using liq. chromatog. under the limiting conditions of desorption (LC LCD). A solvent plug (discrete barrier) is introduced in front of the sample which specifically promotes the adsorption of HDPE segments on the stationary phase (porous graphitic carbon). Under selected thermodn. conditions, VLDPE segments and block copolymer chains crossed the barrier while HDPE segments followed the pore-included barrier solvent and thus enabled sepn. The barrier solvent compn. was optimized and the chem. compn. of fractionated polymer chains was investigated as a function of barrier solvent strength using an online Fourier-transform IR (FTIR) detector. Our study revealed that both the HDPE segments as well as asym. block copolymer chains (HDPE block length » VLDPE block length) are retained in the sepn. and the barrier strength can be tailored to retain a particular compn. At the optimum barrier solvent compn., this method can be applied to sep. effective HDPE segments from the other components, which has been demonstrated using an exptl. OBC sample.
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    50. 50
      Berek D. Macova E. Liquid chromatography under limiting conditions of desorption 6: Separation of a four-component polymer blend J. Sep. Sci. 2015 38 543 549
      50
      Liquid chromatography under limiting conditions of desorption 6: Separation of a four-component polymer blend
      Berek, Dusan; Macova, Eva
      Journal of Separation Science (2015), 38 (4), 543-549CODEN: JSSCCJ; ISSN:1615-9314. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Baseline sepn. was achieved of a model four-component polymer blend of polystyrene-poly(Me methacrylate)-poly(ethylene oxide)-poly(2-vinyl pyridine) in a single chromatog. run with help of the unconventional method of liq. chromatog. under limiting conditions of desorption. Narrow barriers of liqs. were employed, which selectively decelerated elution of particular kinds of macromols. Bare silica gel was the column packing, and the eluent was a mixt. of dimethylformamide/tetrahydrofuran/toluene 30:50:20 wt./wt./w. Barrier compns. were neat toluene, B#1, neat THF, B#2, and dimethylformamide/tetrahydrofuran/toluene 15:55:30, B#3. Minor blend constituents (∼1%) could be identified, as well. The result represents a step toward the sepn. and mol. characterization of triblock-copolymers, many of which are expected to contain besides both parent homopolymers also the diblock chains and thus they are in fact four-component polymer blends.
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    51. 51
      Schollenberger M. Radke W. SEC-Gradients, an alternative approach to polymer gradient chromatography: 1. Proof of the concept Polymer 2011 52 3259 3262
      51
      SEC-Gradients, an alternative approach to polymer gradient chromatography: 1. Proof of the concept
      Schollenberger, Martin; Radke, Wolfgang
      Polymer (2011), 52 (15), 3259-3262CODEN: POLMAG; ISSN:0032-3861. (Elsevier Ltd.)
      A new approach to gradient chromatog. of polymers is presented, in which the sample is introduced at the end of the gradient and elutes within the elution vol. range typical for size exclusion chromatog. (SEC). Due to the gradient the samples are retarded and elute nearly independent of molar mass at the adsorption threshold. The concept was proven for a series of narrowly distributed poly(Me methacrylate)s (PMMA) in a chloroform-tetrahydrofuran (THF) SEC-gradient. The application of the SEC-gradient to a blend of PMMA and polystyrene stds. of similar molar masses, which could not be sepd. by SEC due to their similar hydrodynamic sizes, resulted in a clear sepn. according to chem. compn. Since SEC-gradients allow dissolving the sample in strong eluents, which might result in breakthrough peaks in conventional gradients, the new approach is a valuable alternative to conventional gradient chromatog.
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    52. 52
      Maier H. Malz F. Reinhold G. Radke W. SEC Gradients: An Alternative Approach to Polymer Gradient Chromatography. Separation of Poly(methyl methacrylate-stat-methacrylic acid) by Chemical Composition Macromolecules 2013 46 1119 1123
      52
      SEC Gradients: An Alternative Approach to Polymer Gradient Chromatography. Separation of Poly(methyl methacrylate-stat-methacrylic acid) by Chemical Composition
      Maier, Helena; Malz, Frank; Reinhold, Guenter; Radke, Wolfgang
      Macromolecules (Washington, DC, United States) (2013), 46 (3), 1119-1123CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      The development of a chromatog. method capable to sep. poly(Me methacrylate-stat-methacrylic acid) samples with methacrylic acid contents of up to 50% by chem. compn. is described. For this purpose a gradient ranging from chloroform to dimethylacetamide on a PSS PROTEEMA column was applied. The application of a conventional gradient resulted in severe breakthrough peaks. Therefore, the recently developed concept of SEC gradients was used. No breakthrough peaks were obsd., and the peaks corresponding to samples of different content of methacrylic acid were well resolved. A nearly linear relationship between elution vol. and methacrylic acid content was obsd. The developed method allows detn. of the chem. compn. distribution of the above-mentioned class of polymers.
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    53. 53
      Skvortsov A. M. Gorbunov A. A. Adsorption Effects in the Chromatogrpahy of Polymers J. Chromatogr. 1986 358 77 83
      53
      Adsorption effects in the chromatography of polymers
      Skvortsov, A. M.; Gorbunov, A. A.
      Journal of Chromatography (1986), 358 (1), 77-83CODEN: JOCRAM; ISSN:0021-9673.
      An equil. theory of polymer chromatog. was developed by using the model of a gaussian chain in a slitlike pore at arbitrary energies of interaction between the chain unit and the adsorbent and at any ratio of the chain size, R, to the pore width, D. Five specific regions existed in the chromatog. behavior of macromols., corresponding to different R and D values and different adsorption energies. Anal. expressions for the distribution coeff., K, were obtained for each region. The exptl. dependences of K on R were discussed.
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    54. 54
      Ziebarth J. D. Wang Y. M. Interactions of complex polymers with nanoporous substrate Soft Matter 2016 12 5245 5256
      54
      Interactions of complex polymers with nanoporous substrate
      Ziebarth, Jesse D.; Wang, Yongmei
      Soft Matter (2016), 12 (24), 5245-5256CODEN: SMOABF; ISSN:1744-683X. (Royal Society of Chemistry)
      A review. With the advance of polymer synthesis, polymers that possess unique architectures such as stars or cyclic chains, and unique chem. compn. distributions such as block copolymers or statistical copolymers have become frequently encountered. Characterization of these complex polymer systems drives the development of interactive chromatog. where the adsorption of polymers on the porous substrate in chromatog. columns is finely tuned. Liq. Chromatog. at the Crit. Condition (LCCC) in particular makes use of the existence of the Crit. Adsorption Point (CAP) of polymers on solid surfaces and has been successfully applied to characterization of complex polymer systems. Interpretation and understanding of chromatog. behavior of complex polymers in interactive chromatog. motivates theor./computational studies on the CAP of polymers and partitioning of these complex polymers near the CAP. This review article covers the theor. questions encountered in chromatog. studies of complex polymers.
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    55. 55
      Macko T. Hunkeler D. Liquid chromatography under critical and limiting conditions: A survey of experimental systems for synthetic polymers Adv. Polym. Sci. 2003 163 61 136
      55
      Liquid chromatography under critical and limiting conditions: a survey of experimental systems for synthetic polymers
      Macko, Tibor; Hunkeler, David
      Advances in Polymer Science (2003), 163 (Liquid Chromatography FTIR Microspectroscopy Microwave Assisted Synthesis), 61-136CODEN: APSIDK; ISSN:0065-3195. (Springer-Verlag)
      A review on the sepn. of polymers by liq. chromatog. At the interface between the entropic size exclusion sepn. and the enthalpy-dominated liq. adsorption chromatog. it is possible, exptl., to identify conditions where polymer samples elute independent of their molar mass. These "crit. conditions" function according to theory by compensating the entropy and enthalpy of the sepn. For a series of common and specialty polymers, the mobile phase compns. and temp. which provide the molar mass independent elution behavior, for a given stationary phase, have been extd. from literature and summarized. This collection may help to select, or forecast, suitable LC systems, when an application of liq. chromatog. under crit. conditions for a polymer is required. Correlations between properties of solvents, sorbents and polymers, such as soly. parameters, eluotropic strength and Mark-Houwink consts. have been extd. from the collected data. Specifically, soly. parameters of crit. mobile phases corresponding to a pair polymer-sorbent are in a majority of cases very similar. The elution strength of the first component of a crit. binary eluent correlates linearly with the vol. percent of the second component, esp., when an identical packing gel is applied. However, the crit. conditions are independent of the thermodn. quality of the solvent. Under limiting conditions, the mobile phase may be even a precipitant or a strong adsorption promoting liq. for an injected polymer. Possibilities for increase of the upper molar mass sepn. limit are outlined and influence of sample solvent on elution behavior is described. Applications of liq. chromatog. under conditions of enthalpy-entropy compensation for sepn. of homo- and copolymers are also, briefly, summarized.
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    56. 56
      Pasch H. Chromatographic investigations of macromolecules in the critical range of liquid chromatography: 3. Analysis of polymer blends Polymer 1993 34 4095 4099
      56
      Chromatographic investigations of macromolecules in the critical range of liquid chromatography. 3. Analysis of polymer blends
      Pasch, H.
      Polymer (1993), 34 (19), 4095-9CODEN: POLMAG; ISSN:0032-3861.
      Polymer blends of various compns. were analyzed by liq. chromatog. at the crit. point of adsorption. By operating at the crit. point of one blend component, it is possible to sep. the blend regardless of the chem. structure and the molar mass of the second blend component. In addn., the molar mass and the molar-mass distribution of the second blend component may be detd. via a conventional size exclusion chromatog. procedure. It is shown that, in addn. to homopolymer blends, blends comprising a copolymer as one component may be sepd.
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    57. 57
      Pasch H. Rode K. Chaumien N. Chromatographic Investigations of Macromolecules in the Critical Range of Liquid Chromatography .9. Separation of Methacrylate-Based Polymer Blends Polymer 1996 37 4079 4083
      57
      Chromatographic investigations of macromolecules in the critical range of liquid chromatography. 9. Separation of methacrylate-based polymer blends
      Pasch, H.; Rode, K.; Chaumien, N.
      Polymer (1996), 37 (18), 4079-4083CODEN: POLMAG; ISSN:0032-3861. (Elsevier)
      Binary polymer blends of polymethacrylates were sepd. by liq. chromatog. at the crit. point of adsorption. The polymers were: poly(Me methacrylate) (PMMA), poly(t-Bu methacrylate) (PtBMA), poly(Bu methacrylate) (PnBMA), and poly(decyl methacrylate) (PDMA) and the mobile phase was methyl-Et ketone (MEK) and MEK-cyclohexane. By operating at chromatog. conditions corresponding to the crit. point of one blend component, the blends were sepd. regardless of the molar-mass distributions of the components. Depending on the polarity of the components, polar or non-polar stationary phases must be used. Operating at the crit. point of PMMA, less polar methacrylates can be analyzed using silica gel as the stationary phase and MEK-cyclohexane as the eluent. For the anal. of polar polymethacrylates at the crit. point of PDMA, a reversed stationary phase and tetrahydrofuran-acetonitrile are a useful combination.
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    58. 58
      Bashir M. A. Radke W. Predicting the chromatographic retention of polymers: Poly(methyl methacrylate)s and polyacryate blends J. Chromatogr. A 2007 1163 86 95
      58
      Predicting the chromatographic retention of polymers: Poly(methyl methacrylate)s and polyacrylate blends
      Bashir, Mubasher A.; Radke, Wolfgang
      Journal of Chromatography A (2007), 1163 (1-2), 86-95CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
      The suitability of a retention model esp. designed for polymers is investigated to describe and predict the chromatog. retention behavior of poly(Me methacrylate)s as a function of mobile phase compn. and gradient steepness. It is found that three simple yet rationally chosen chromatog. expts. suffice to ext. the analyte specific model parameters necessary to calc. the retention vols. This allows predicting accurate retention vols. based on a min. no. of initial expts. Therefore, methods for polymer sepns. can be developed in relatively short time. The suitability of the virtual chromatog. approach to predict the sepn. of polymer blend is demonstrated for the first time using a blend of different polyacrylates.
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    59. 59
      Zimina T. M. Kever J. J. Melenevskaya E. Y. Fell A. F. Analysis of Block Copolymers by High-Performance Liquid Chromatography under Critical Condition J. Chromatogr. 1992 593 233 241
      59
      Analysis of block copolymers by high-performance liquid chromatography under critical conditions
      Zimina, T. M.; Kever, J. J.; Melenevskaya, E. Yu.; Fell, A. F.
      Journal of Chromatography (1992), 593 (1-2), 233-41CODEN: JOCRAM; ISSN:0021-9673.
      The exptl. validity of the concept of so-called chromatog. "invisibility" in the complete chromatog. characterization of block copolymers (mol. wt. vs. chem. compn.), predicted theor. by Gorbunov and Skvortsov (1988) on the basis of the phenomenon of crit. conditions in liq. chromatog., was examd. The theor. approach predicts the possibility of 1 component of an A-B block copolymer being eluted under gel permeation chromatog. conditions, whereas the size of the alternate "invisible" component exerts no effect on the overall elution profile of the block copolymer. This applies only when special thermodn. conditions, i.e, eluent compn. and temp., are fulfilled, where the distribution coeff. is unity, regardless of mol. wt. Me methacrylate-styrene (I) block copolymers and I-tert-Bu methacrylate copolymer were used as examples with binary and ternary mixts. of acetonitrile-CH2Cl2, MeOH-CHCl3, THF-CH2Cl2, and THF-CH2Cl2-hexane as eluents for chromatog. under crit. conditions on wide-pore silica gel in narrow-bore columns.
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    60. 60
      Pasch H. Brinkmann C. Much H. Just U. Chromatographic investigations of macromolecules in the “critical range” of liquid chromatography II. Two-dimensional separations of poly(ethylene oxide-block-propylene oxide) J. Chromatogr. 1992 623 315
      60
      Chromatographic investigations of macromolecules in the "critical range" of liquid chromatography II. Two-dimensional separations of poly(ethylene oxide-block-propylene oxide)
      Pasch, H.; Brinkmann, C.; Much, H.; Just, U.
      Journal of Chromatography (1992), 623 (2), 315-22CODEN: JOCRAM; ISSN:0021-9673.
      An ethylene oxide-propylene oxide block copolymer (I) was characterized with respect to molar mass distribution and block length of the individual blocks using 2-dimensional chromatog. techniques. In the first dimension I was sepd. according to the length of the poly(propylene oxide) (II) block by liq. chromatog. at the crit. point of adsorption. The resulting II uniform fractions were subjected to supercrit. fluid chromatog. or size-exclusion chromatog. and the av. length and molar mass of the poly(ethylene oxide) blocks were detd. for every fraction.
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    61. 61
      Pasch, H.; Trathnigg, B. HPLC of Polymers; Springer-Verlag: Berlin, 1997.
      There is no corresponding record for this reference.
    62. 62
      Falkenhagen J. Much H. Stauf W. Muller A. H. E. Characterization of block copolymers by liquid adsorption chromatography at critical conditions. 1. Diblock copolymers Macromolecules 2000 33 3687 3693
      62
      Characterization of Block Copolymers by Liquid Adsorption Chromatography at Critical Conditions. 1. Diblock Copolymers
      Falkenhagen, Jana; Much, Helmut; Stauf, Wolfgang; Mueller, Axel H. E.
      Macromolecules (2000), 33 (10), 3687-3693CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Liq. adsorption chromatog. at crit. conditions (LACCC) in normal and in reversed-phase modes provides independent information on the molar mass distributions of both blocks of poly(Me methacrylate)-block-poly(tert-Bu methacrylate), even if no information about the precursor is available. In addn., the amt. of unreacted precursor can be detd., even if its molar mass is comparable to that of the total block copolymer. The reversal of elution order by changing of stationary and mobile phases makes it possible to independently characterize each block in the SEC mode of the LACCC system. Thus, complete structural information is obtained even without using two-dimensional chromatog. techniques.
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    63. 63
      Lee W. Cho D. Chang T. Hanley K. J. Lodge T. P. (LCCC)Characterization of polystyrene-b-polyisoprene diblock copolymers by liquid chromatography at the chromatographic critical condition Macromolecules 2001 34 2353 2358
      63
      Characterization of Polystyrene-b-polyisoprene Diblock Copolymers by Liquid Chromatography at the Chromatographic Critical Condition
      Lee, Wonmok; Cho, Donghyun; Chang, Taihyun; Hanley, Kenneth J.; Lodge, Timothy P.
      Macromolecules (2001), 34 (7), 2353-2358CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      In the chromatog. sepn. of macromols. with a porous stationary phase, the retention is detd. by both size exclusion and interaction mechanisms. At the chromatog. crit. condition, the effects due to the 2 sepn. mechanisms compensate each other, and the retention of homopolymer mols. becomes independent of mol. wt. Liq. chromatog. at the crit. condition has attracted much interest for the characterization of block copolymers since it might permit the characterization of individual blocks of a block copolymer by making one block chromatog. invisible. This method is examd. using 2 sets of styrene-isoprene block copolymers designed to have one block length const. while varying the other block length. For these block copolymer systems, a block cannot be made completely invisible at the crit. condition of its homopolymer, and the retention of block copolymers is affected to some extent by the length of the invisible block under its chromatog. crit. condition.
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    64. 64
      Belenky B. G. Valchikhina M. D. Vakhtina I. A. Gankina E. S. Tarakanov O. G. Thin-Layer Chromatography of Oligomers J. Chromatogr. 1976 129 115 124
      There is no corresponding record for this reference.
    65. 65
      Entelis S. G. Evreinov V. V. Gorshkov A. V. Functionality and molecular weight distribution of Telechelic polymers Adv. Polym. Sci. 1986 76 129 175
      There is no corresponding record for this reference.
    66. 66
      Gorshkov A. V. Much H. Becker H. Pasch H. Evreinov V. V. Entelis S. G. Chromatographic investigations of macromolecules in the “critical range” of liquid chromatography I. Functionality type and composition distribution in polyethylene oxide and polypropylene oxide copolymers J. Chromatogr. A 1990 523 91 102
      66
      Chromatographic investigations of macromolecules in the "critical range" of liquid chromatography. I. Functionality type and composition distribution in polyethylene oxide and polypropylene oxide copolymers
      Gorshkov, A. V.; Much, H.; Becker, H.; Pasch, H.; Evreinov, V. V.; Entelis, S. G.
      Journal of Chromatography (1990), 523 (), 91-102CODEN: JOCRAM; ISSN:0021-9673.
      Polyoxyalkylenes obtained from ethylene oxide (I) and propylene oxide (II) and corresponding copolyethers were analyzed by liq. chromatog. under crit. conditions (near the crit. point of polymer adsorption) to obtain information on the functionality type distribution and structural inhomogeneity of copolymers. Homopolyether species were sepd. according to the no. and type of their end groups. Copolymers of I and II (random and block) were split into groups depending on chem. compn., block length, and the character of order in the monomer distribution.
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    67. 67
      Baran K. Laugier S. Cramail H. Fractionation of functional polystyrenes, poly(ethylene oxide)s and poly(styrene)-b-poly(ethylene oxide) by liquid chromatography at the exclusion-adsorption transition point J. Chromatogr. B 2001 753 139 149
      67
      Fractionation of functional polystyrenes, poly(ethylene oxide)s and poly(styrene)-b-poly(ethylene oxide) by liquid chromatography at the exclusion-adsorption transition point
      Baran, K.; Laugier, S.; Cramail, H.
      Journal of Chromatography B: Biomedical Sciences and Applications (2001), 753 (1), 139-149CODEN: JCBBEP; ISSN:0378-4347. (Elsevier Science B.V.)
      The fractionation of functional polystyrene (PS) and poly(ethylene oxide) (PEOs) as well as their block copolymers, by liq. chromatog. at the exclusion adsorption transition point, also called crit. conditions mode, is reported. In this specific elution mode, the fractionation is only governed by the nature and the no. of functions attached to the polymer backbone, independent of the molar mass distribution of the whole sample. Functionally-terminated PS can be readily sepd. from non-functional PS under various chromatog. conditions. The technique also allows the fractionation of PEO and PS-PEO block copolymers. In the latter cases, moderately polar columns and water-based polar eluents were required to attain satisfactory fractionation.
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    68. 68
      Jiang X. L. Schoenmakers P. J. Lou X. W. Lima V. van Dongen J. L. J. Brokken-Zijp J. Separation and characterization of functional poly(n-butyl acrylate) by critical liquid chromatography J. Chromatogr. A 2004 1055 123 133
      68
      Separation and characterization of functional poly(n-butyl acrylate) by critical liquid chromatography
      Jiang, Xulin; Schoenmakers, Peter J.; Lou, Xianwen; Lima, Vincent; van Dongen, Joost L. J.; Brokken-Zijp, Jose
      Journal of Chromatography A (2004), 1055 (1-2), 123-133CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
      The sepn. of functional poly(Bu acrylate) (PnBA) polymers based on the no. of end-groups under crit. liq. chromatog. (LC) conditions has been studied using a bare-silica column. The (near-) crit. solvent compns. for non-, mono-, and difunctional (telechelic) carboxyl-PnBAs were detd. in normal-phase LC, using mixts. of acetonitrile, acetic (or formic) acid, and dichloromethane of varying compn. Some formic or acetic acid had to be added to the mobile phase to elute PnBA polymers with carboxyl end-groups. The crit. solvent compns. obtained were not exactly the same for non-, mono-, and difunctional PnBA polymers. These were unusual exptl. observation, but they were in agreement with theoretic predictions. Nevertheless, low-mol.-mass PnBA samples were successfully sepd. according to the carboxyl functionality at (near-) crit. conditions. With the aid of mass spectrometry (MS), the (near-) crit. sepn. of low-mol.-wt. PnBA polymers was confirmed to be mainly based on the carboxyl functionality. Calibration curves for evaporative light-scattering detection (ELSD) were used for quant. anal. of carboxyl-functional PnBA polymers. The results proved that nearly ideal functionalities (av. no. of carboxyl end-groups per mol. up to 1.99) were achieved for telechelic PnBAs prepd. by one-step reversible addn.-fragmentation chain-transfer (RAFT) polymn. of PnBA.
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    69. 69
      Im K. Kim Y. Chang T. Lee K. Choi N. Separation of branched polystyrene by comprehensive two-dimensional liquid chromatography J. Chromatogr. A 2006 1103 235 242
      69
      Separation of branched polystyrene by comprehensive two-dimensional liquid chromatography
      Im, Kyuhyun; Kim, Youngtak; Chang, Taihyun; Lee, Kwanyoung; Choi, Namsun
      Journal of Chromatography A (2006), 1103 (2), 235-242CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
      Branched polystyrenes (PS) featuring a bivariate distribution in the mol. wt. and in the no. of branches were characterized by comprehensive two-dimensional liq. chromatog. (2D-LC). The branched PS were prepd. by anionic polymn. using BuLi as an initiator and a subsequent linking reaction with p-(chlorodimethylsilyl)styrene (CDMSS). The BuLi initiator yields polystyryl anions with broad mol. wt. distribution (MWD) and the linking reaction with CDMSS yields branched PS with different no. of branches. For the first dimension (1st-D) sepn., reversed-phase temp. gradient interaction chromatog. (RP-TGIC) was employed to sep. the branched polymer according to mainly the mol. wt. In the second dimension (2nd-D) sepn., the effluents from the RP-TGIC sepn. are subjected to liq. chromatog. at chromatog. crit. conditions (LCCC), in which the sepn. was carried out at the crit. condition of linear homo-PS to sep. the branched PS in terms of the no. of branches. The 2D-LC resoln. of RP-TGIC × LCCC combination worked better than the common LCCC × size-exclusion chromatog. (SEC) configuration due to the higher resoln. of RP-TGIC in mol. wt. than SEC. Furthermore, by virtue of using the same eluent in RP-TGIC and LCCC (only the column temp. is different), RP-TGIC × LCCC sepn. is free from possible 'break through' and large system peak problems. This type of 2D-LC sepn. could be utilized efficiently for the anal. of branched polymers with branching units distinguishable by LC sepn.
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    70. 70
      Petit C. Luneau B. Beaudoin E. Gigmes D. Bertin D. Liquid chromatography at the critical conditions in pure eluent: An efficient tool for the characterization of functional polystyrenes J. Chromatogr. A 2007 1163 128 137
      70
      Liquid chromatography at the critical conditions in pure eluent: An efficient tool for the characterization of functional polystyrenes
      Petit, Christelle; Luneau, Benoit; Beaudoin, Emmanuel; Gigmes, Didier; Bertin, Denis
      Journal of Chromatography A (2007), 1163 (1-2), 128-137CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
      Functional polymers are usually sepd. by liq. chromatog. at crit. conditions (LC-CC) using a desorli/adsorli mixt. as eluent. In this paper, we describe LC-CC using DMF as pure eluent at 72° and its application to the anal. of functional polystyrenes. The crit. adsorption point is reached by tuning the temp. so that the lack of repeatability is no longer a problem. We analyzed several batches of polystyrenes, exhibiting different mol. wts. and functionalities. We were able to differentiate di-, mono- and non-functional polystyrenes, bearing carboxylic acid, hydroxyl or nitroxide moieties. The behavior of these polystyrenes expressed by the exptl. results was compared with their behavior described by the LC-CC theory through the calcn. of the effective interaction parameter of each end group. The technique also makes it possible to quantify the fractions of different functional polymers in a blend.
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    71. 71
      Oh J. Kuk J. Lee T. Ye J. Paik H. J. Lee H. W. Chang T. Molecular Weight Distribution of Living Chains in Polystyrene Prepared by Atom Transfer Radical Polymerization ACS Macro Lett. 2017 6 758 761
      71
      Molecular Weight Distribution of Living Chains in Polystyrene Prepared by Atom Transfer Radical Polymerization
      Oh, Joongsuk; Kuk, Jiae; Lee, Taeheon; Ye, Jihwa; Paik, Hyun-jong; Lee, Hyo Won; Chang, Taihyun
      ACS Macro Letters (2017), 6 (7), 758-761CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
      Living and dead chains of a polystyrene synthesized by atom transfer radical polymn. were sepd. and characterized by high performance liq. chromatog. (HPLC), size exclusion chromatog. (SEC), NMR, and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The bromine end group in the living chain was quant. converted to a hydroxyl end group via first azidation and subsequent copper-catalyzed azide-alkyne cycloaddn. (CuAAC) click reaction with propargyl alc. The living chains bearing a polar end group are fully resolved from the unmodified dead chains by HPLC sepn. using a bare silica stationary phase. Mol. wt. distributions (MWD) of the living and dead chain are characterized by SEC and MALDI-MS. The MWD of the living chains is close to a Poisson distribution. Interestingly, the elution peak of the living chains in the HPLC sepn. split into two. The peak split is attributed to the diastereomeric structure of the chain end by NMR and MALDI-MS analyses.
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    72. 72
      Ziebarth J. D. Gardiner A. A. Wang Y. M. Jeong Y. Ahn J. Jin Y. Chang T. Comparison of Critical Adsorption Points of Ring Polymers with Linear Polymers Macromolecules 2016 49 8780 8788
      There is no corresponding record for this reference.
    73. 73
      Ahn J. Chang T. Wang X. Limpouchova Z. Prochazka K. Influence of the Chain Architecture and the Presence of End-Groups or Branching Units Chemically Different from Repeating Structural Units on the Critical Adsorption Point in Liquid Chromatography Macromolecules 2017 50 8720 8730
      73
      Influence of the Chain Architecture and the Presence of End-Groups or Branching Units Chemically Different from Repeating Structural Units on the Critical Adsorption Point in Liquid Chromatography
      Ahn, Junyoung; Chang, Taihyun; Wang, Xiu; Limpouchova, Zuzana; Prochazka, Karel
      Macromolecules (Washington, DC, United States) (2017), 50 (21), 8720-8730CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      The crit. adsorption point (CAP) of linear and star-shaped polymers was studied by normal phase and reversed phase liq. chromatog. (NPLC and RPLC) and computer simulation. Three sets of polystyrenes (PS) differing in chain architecture and chem. distinct groups were prepd.: linear PS (sec-Bu and hydrogen end group), 2-arm PS (linear, two sec-Bu end groups and one silyl group in the middle of the chain) and 4-arm star-shaped PS (four sec-Bu end groups and one silyl group in the center of the star). The column temp. at CAP, TCAP (linear PS) = TCAP (2-arm PS) > TCAP (4-arm PS) in both RPLC and NPLC which can be attributed to the variation in chain architecture. However, the elution times at CAP of three polymers are all different: In NPLC, tE,CAP (linear) > tE,CAP (2-arm PS) > tE,CAP (4-arm PS) while in RPLC, tE,CAP (4-arm PS) > tE,CAP (2-arm PS) > tE,CAP (linear). The variation of tE,CAP can be explained by the contribution of the chem. distinct groups. The computer simulation results are in good agreement with the chromatog. expts. results and support the interpretation of exptl. data.
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    74. 74
      Gorbunov A. A. Skvortsov A. M. Theory of Chromatographic Separation of Linear and Ring Macromolecules Polym. Sci. USSR 1987 29 1025 1031
      There is no corresponding record for this reference.
    75. 75
      Pasch H. Deffieux A. Henze I. Schappacher M. Riquelurbet L. Analysis of Macrocyclic Polystyrenes .1. Liquid Chromatographic Investigations Macromolecules 1996 29 8776 8782
      75
      Analysis of Macrocyclic Polystyrenes. 1. Liquid Chromatographic Investigations
      Pasch, Harald; Deffieux, Alain; Henze, Inka; Schappacher, Michel; Rique-Lurbet, Laurence
      Macromolecules (1996), 29 (27), 8776-8782CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Macrocyclic polystyrenes prepd. by a single-step, pseudo-unimol. cyclization of a linear α-(diethoxyethyl)-ω-styrenylpolystyrene can effectively be analyzed by liq. chromatog. at the crit. point of adsorption. Using silica gel as the stationary phase and THF-hexane as the eluent, the macrocyclic oligomers are sepd. from their linear precursors and other nonfunctional linear oligomers. The quant. detn. of the cyclization yield can be carried out via appropriate detector calibration for the linears and cyclics. Addnl. information on the chem. structure of the linears and cyclics is obtained by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. In conclusion, a possible cyclization mechanism is given including an interpretation of the MALDI behavior of the samples.
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    76. 76
      Lepoittevin B. Dourges M. A. Masure M. Hemery P. Baran K. Cramail H. Synthesis and characterization of ring-shaped polystyrenes Macromolecules 2000 33 8218 8224
      76
      Synthesis and Characterization of Ring-Shaped Polystyrenes
      Lepoittevin, Benedicte; Dourges, Marie-Anne; Masure, Michele; Hemery, Patrick; Baran, Katia; Cramail, Henri
      Macromolecules (2000), 33 (22), 8218-8224CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Macrocyclic polystyrenes were prepd. by coupling a two-ended living precursor dianions with 1,3-bis(1-phenylvinyl)benzene (DDPE). Expts. were performed in a dry box app., and macrocycles were obtained with a yield ranged between 40 and 55%. Simultaneously, besides the expected cyclic polymer, polycondensates (linear and cyclic) were formed. Thus, macrocyclic products were sepd. from the residual linear precursor and linear polycondensates byproducts by preparative high performance liq. chromatog. at the exclusion-adsorption transition point. Isolation of highly pure cyclic polystyrenes (of different sizes) was carried out. Information on the chem. structure of the linear and cyclic polystyrenes were obtained by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, showing a good agreement with the expected structures. In addn., viscometry measurements by SEC (viscometry detector) showed that the ratio g' = [η]C/[η]L is equal to 0.67 in a good solvent and confirmed the high efficiency of the preparative liq. chromatog. sepn.
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    77. 77
      Lee H. C. Lee H. Lee W. Chang T. Roovers J. Fractionation of cyclic polystyrene from linear precursor by HPLC at the chromatographic critical condition Macromolecules 2000 33 8119 8121
      77
      Fractionation of Cyclic Polystyrene from Linear Precursor by HPLC at the Chromatographic Critical Condition
      Lee, Hee Cheong; Lee, Hyunjung; Lee, Wonmok; Chang, Taihyun; Roovers, Jacques
      Macromolecules (2000), 33 (22), 8119-8121CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      The fractionation of cyclic polystyrene from linear contaminants by HPLC at the crit. condition is reported.
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    78. 78
      Lee W. Lee H. Lee H. C. Cho D. Chang T. Gorbunov A. A. Roovers J. Retention Behavior of linear and ring polystyrene at the chromatographic critical condition Macromolecules 2002 35 529 538
      78
      Retention Behavior of Linear and Ring Polystyrene at the Chromatographic Critical Condition
      Lee, Wonmok; Lee, Hyunjung; Lee, Hee Cheong; Cho, Donghyun; Chang, Taihyun; Gorbunov, Alexei A.; Roovers, Jacques
      Macromolecules (2002), 35 (2), 529-538CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Chromatog. retention of linear and ring polystyrene was studied near the chromatog. crit. condition. Reversed phase silica columns of four different pore sizes were employed to examine the pore size dependence. Adjusting the column temp., the crit. condition for linear polystyrene was searched for each column with a mixed mobile phase of CH2Cl2/CH3CN (57/43 vol./vol.). It was practically impossible to establish an unambiguous crit. condition with a single pore size column for a wide mol. wt. range of polystyrenes, in particular with narrow pore size columns. At the best available condition, retentions of nine different mol. wt. ring polystyrenes were measured relative to their linear precursors for each pore-sized column. As predicted theor., the partition coeff. (K) of ring polymers vs. the size ratio of polymer chain to pore (R/d) shows a good linear relation in the large pore regime (R/d « 1). This linearity is universal for all the pore sizes, which is consistent with the theor. prediction. However, the K vs. R/d dependency at the large pore regime did not follow the theor. prediction quant. In the narrow-pore regime (R/d » 1) the exptl. results did not follow the theory for ideal-chain ring macromols. even qual. To explain the obsd. chromatog. behavior at R/d » 1, the scaling theory accounting for the polymer excluded vol. was used, and the definition of the crit. condition was revised. This anal. gave some keys for understanding the results at R/d » 1 and revealed the possible nonequivalence of the conditions for theory and expt. as the most probable reason for obsd. discrepancies.
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    79. 79
      Takano A. Kushida Y. Aoki K. Masuoka K. Hayashida K. Cho D. Kawaguchi D. Matsushita Y. HPLC Characterization of Cyclization Reaction Product Obtained by End-to-End Ring Closure Reaction of a Telechelic Polystyrene Macromolecules 2007 40 679 681
      79
      HPLC Characterization of Cyclization Reaction Product Obtained by End-to-End Ring Closure Reaction of a Telechelic Polystyrene
      Takano, Atsushi; Kushida, Yuuki; Aoki, Kayoko; Masuoka, Keisuke; Hayashida, Kenichi; Cho, Donghyun; Kawaguchi, Daisuke; Matsushita, Yushu
      Macromolecules (2007), 40 (3), 679-681CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Cyclization reaction product synthesized by the end-to-end ring closure reaction of a telechelic polystyrene with mol. wt. of 38K in extremely dil. conditions was carefully characterized by using two kinds of HPLC techniques, i.e., liq. chromatog. at the crit. condition (LCCC) and size exclusion chromatog. (SEC). First, the cyclization reaction product was coarsely sepd. into linear species and cyclic ones by LCCC; second, each fraction was further sepd. by high-resoln. SEC. It was found from the HPLC analyses that the cyclization reaction product contains both linear and cyclic condensation products. Furthermore, dimeric, trimeric, and more multimeric cyclic mols. with reasonable abundance were identified as well as the monomeric cyclic mol. with high yield, as much as 50%, in the cyclic products.
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    80. 80
      Kapnistos M. Lang M. Vlassopoulos D. Pyckhout-Hintzen W. Richter D. Cho D. Chang T. Rubinstein M. Unexpected power-law stress relaxation of entangled ring polymers Nat. Mater. 2008 7 997 1002
      80
      Unexpected power-law stress relaxation of entangled ring polymers
      Kapnistos, M.; Lang, M.; Vlassopoulos, D.; Pyckhout-Hintzen, W.; Richter, D.; Cho, D.; Chang, T.; Rubinstein, M.
      Nature Materials (2008), 7 (12), 997-1002CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
      Long linear and branched polymers have a characteristic entanglement plateau and stress relaxation proceeds by chain reptation or branch retraction. In both mechanisms, the presence of chain ends is essential. Properly purified high-mol. wt. ring polystyrene, exhibits self-similar dynamics, yielding a power-law stress relaxation. However, trace amts. of linear polymer chains at a concn. almost two decades below the overlap caused an enhanced mech. response. An entanglement plateau was recovered at higher concns. of linear chains. The results are useful as a tool for manipulation of properties of polymers and for tuning the rheol. of entangled polymers.
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    81. 81
      Pasch H. Analysis of complex polymers by multidimensional techniques. Phys. Chem. Chem. Phys. 1999 1 3879 3890
      81
      Analysis of complex polymers by multidimensional techniques. Invited Lecture
      Pasch, Harald
      Physical Chemistry Chemical Physics (1999), 1 (17), 3879-3890CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      A review with 53 refs. Complex polymers are distributed in more than one way in terms of mol. heterogeneity. In addn. to the molar mass distribution, they are frequently distributed with respect to chem. compn., functionality, mol. architecture. For the characterization of the different types of mol. heterogeneity it is necessary to use a wide range of anal. techniques. Preferably, these techniques should be selective towards a specific type of heterogeneity. The combination of 2 selective anal. techniques is assumed to yield 2-dimensional information on the mol. heterogeneity. The principles of combining different anal. techniques in multidimensional anal. schemes are discussed. The most promising protocols for coupled techniques are the combination of 2 different chromatog. methods and the combination of chromatog. and spectroscopy. The basic principles of 2-dimensional chromatog. are considered, combining interaction chromatog. and size exclusion chromatog. In the use of liq. chromatog. with selective detectors, the coupling of different chromatog. techniques with Fourier-transform IR and NMR spectroscopies and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry is highlighted.
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    82. 82
      Kilz P. Two-dimensional chromatography as an essential means for understanding macromolecular structure Chromatographia 2004 59 3 14
      82
      Two-dimensional chromatography as an essential means for understanding macromolecular structure
      Kilz, P.
      Chromatographia (2004), 59 (1/2), 3-14CODEN: CHRGB7; ISSN:0009-5893. (Vieweg Verlag/GWV Fachverlage GmbH)
      A review. Current liq. chromatog. techniques allow to det. distributions of various properties for macromols. The polydisperse nature of macromols. regulates the structure-property relationship and is responsible for the vast degree of fine-tuning of application properties. The understanding of macromol. structure is fundamental for the use of polymers in increasingly specific applications. The coexistence of property distributions requires multi-dimensional (combined) chromatog. methodologies. The use and implementation of two-dimensional (2D) sepn. methods and their benefits are described in this paper for synthetic polymers. Similar approaches were used successfully for mapping complex natural and bio-polymers.
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    83. 83
      Berek D. Two-dimensional liquid chromatography of synthetic polymers Anal. Bioanal. Chem. 2010 396 421 441
      83
      Two-dimensional liquid chromatography of synthetic polymers
      Berek, Dusan
      Analytical and Bioanalytical Chemistry (2010), 396 (1), 421-441CODEN: ABCNBP; ISSN:1618-2642. (Springer)
      A review. Two-dimensional liq. chromatog., 2D-LC of synthetic polymers is critically assessed. Similarities and differences of 2D-LC of low-mol.-mass and polymeric substances are reviewed. The rationale of application of 2D-LC to macromol. substances is discussed. Basic information on retention mechanisms in liq. chromatog. of synthetic polymers is furnished. The principles, reasons, and significance of coupling of retention mechanisms are explained. The resulting sepn. processes are elucidated, and the tech. concepts of the corresponding exptl. arrangements are described. The benefits of 2D-LC are demonstrated together with numerous problems and shortcomings of the method. Figure Schematic diagram of contour plot of the results of 2D-LC sepn. A complex polymer system contains three constituents, each with both compn. and molar mass distribution. Sample concn. is visualized by use of color, with concn. increasing from blue to yellow.
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    84. 84
      Baumgaertel A. Altuntaş E. Schubert U. S. Recent developments in the detailed characterization of polymers by multidimensional chromatography J. Chromatogr. A 2012 1240 1 20
      84
      Recent developments in the detailed characterization of polymers by multidimensional chromatography
      Baumgaertel, Anja; Altuntas, Esra; Schubert, Ulrich S.
      Journal of Chromatography A (2012), 1240 (), 1-20CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
      A review. Synthetic polymers as well as biopolymers reveal complex structures, such as variations in functionality, chain length and architecture. Therefore, combinations of different chromatog. techniques are a prerequisite for a detailed characterization. One possible approach is the combination of high performance liq. chromatog. at crit. conditions (LCCC) and size-exclusion chromatog., also named as two-dimensional chromatog., which allows the sepn. of the polymers according to different properties, like molar mass, chem. compn. or functionality. In addn., LCCC hyphenated with different mass spectrometry techniques, e.g. MALDI-TOF or ESI-TOF, leads to addnl. information about mol. details of the polymeric structure. We summarize in this article the recent developments in two-dimensional chromatog. of synthetic polymers and biopolymers since 2005.
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    85. 85
      Schoenmakers P. Aarnoutse P. Multi-Dimensional Separations of Polymers Anal. Chem. 2014 86 6172 6179
      85
      Multi-Dimensional Separations of Polymers
      Schoenmakers, Peter; Aarnoutse, Petra
      Analytical Chemistry (Washington, DC, United States) (2014), 86 (13), 6172-6179CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
      Synthetic polymers and comprehensive two-dimensional liq. chromatog. (LC×LC) are a synergistic combination. LC×LC provides unique insights in mutually dependent mol. distributions. Synthetic polymers offer clear demonstrations of the value of LC×LC.
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    86. 86
      Jiang X. L. van der Horst A. Schoenmakers P. J. Breakthrough of polymers in interactive liquid chromatography J. Chromatogr. A 2002 982 55 68
      86
      Breakthrough of polymers in interactive liquid chromatography
      Jiang, Xulin; van der Horst, Aschwin; Schoenmakers, Peter J.
      Journal of Chromatography A (2002), 982 (1), 55-68CODEN: JCRAEY; ISSN:0021-9673. (Elsevier Science B.V.)
      Two sep. peaks are obsd. for narrow polymer stds. in both isocratic and gradient HPLC. One peak appears around the solvent front (the solvent-plug peak or breakthrough peak), whereas the 2nd peak is retained significantly-or even highly. Although the effect was obsd. many times before, it has never been rigorously explained. The authors provide a detailed explanation for the breakthrough peak. The two completely sep. peaks are demonstrated not to represent to different fractions of the sample (e.g., the low- and high-mol.-mass parts of the distribution). Both peaks are representative of the entire polymeric sample for narrow polymer std. Because the amt. of the polymer in the breakthrough peak may vary, the quant. anal. of the polymers by LC is jeopardized. The effects of the sample solvent, the (initial) mobile phase compn., the injection vol., the injected sample concn., the column temp., and the analyte structure and mol. mass on the breakthrough peak were studied in LC expts. involving stds. of polystyrene and poly(Me methacrylate). Three necessary and sufficient conditions are suggested for the breakthrough phenomenon to be obsd. Recommendations to avoid the breakthrough phenomenon are given, culminating in a structured method for selecting the best possible sample solvents.
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    87. 87
      Gerber J. Radke W. Separation of linear and star-shaped polystyrenes by two-dimensional chromatography E-Polymers 2005
      There is no corresponding record for this reference.
    88. 88
      Pasch H. Kilz P. Fast liquid chromatography for high-throughput screening of polymers Macromol. Rapid Commun. 2003 24 104 108
      88
      Fast liquid chromatography for high-throughput screening of polymers
      Pasch, Harald; Kilz, Peter
      Macromolecular Rapid Communications (2003), 24 (1), 104-108CODEN: MRCOE3; ISSN:1022-1336. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Liq. chromatog. of polymers is traditionally a slow technique with anal. times of typically 30 min per sample. For the application of liq. chromatog. techniques to combinatorial materials research the anal. time per sample must be reduced considerably. Anal. time in SEC can be reduced to about 2 min per sample when high-throughput columns are used. For HPLC small columns with improved sepn. efficiencies can be used. As compared to conventional technol., time savings of more than 80% are achieved.
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    89. 89
      Popovici S. T. Schoenmakers P. J. Fast size-exclusion chromatography - Theoretical and practical considerations J. Chromatogr. A 2005 1099 92 102
      89
      Fast size-exclusion chromatography-Theoretical and practical considerations
      Popovici, Simona T.; Schoenmakers, Peter J.
      Journal of Chromatography A (2005), 1099 (1-2), 92-102CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
      Fast SEC is a very interesting modification of conventional SEC. The need for it emerges from combinatorial chem. and high-throughput experimentation, where high-speed analyses are required. The different approaches to change the speed of anal. are extensively described. Special attention is paid to the trade-off between anal. time and resoln. and to the selection of optimal column lengths and flow rates. Simulations were used to design and to understand expts. Integrity plots are constructed to judge the quality of various SEC systems. Fast sepns. in size-exclusion chromatog. are more favorable than suggested by conventional theory. The results are based on exptl. data obtained for polystyrene using THF as mobile phase.
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    90. 90
      Cho H. Park S. Ree M. Chang T. Y. Jung J. C. Zin W. C. High temperature size exclusion chromatography Macromol. Res. 2006 14 383 386
      90
      High temperature size exclusion chromatography
      Cho, Heesook; Park, Soojin; Ree, Moonhor; Chang, Taihyun; Jung, Jin Chul; Zin, Wang Cheol
      Macromolecular Research (2006), 14 (3), 383-386CODEN: MRAECT; ISSN:1598-5032. (Polymer Society of Korea)
      High-temp. size exclusion chromatog. (SEC) was used widely for the characterization of cryst. polymers, for which high temp. operation above the polymer melting temp. is required to dissolve the polymers. However, this high temp. operation has many advantages in SEC sepn. in addn. to merely increasing polymer soly. At high temp. the eluent viscosity decreases, which in turn decreases the column back-pressure and increases the diffusivity of the analytes. Therefore, many reports on the high temp. operation of HPLC have focused on shortening the anal. time and enhancing the resoln. However, the application of high temp. SEC anal. to exploit the merits of high temp. operation is scarce. Therefore, it is reported on a new app. design for high temp. SEC.
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    91. 91
      Uliyanchenko E. Schoenmakers P. J. van der Wal S. Fast and efficient size-based separations of polymers using ultra-high-pressure liquid chromatography J. Chromatogr. A 2011 1218 1509 1518
      91
      Fast and efficient size-based separations of polymers using ultra-high-pressure liquid chromatography
      Uliyanchenko, Elena; Schoenmakers, Peter J.; van der Wal, Sjoerd
      Journal of Chromatography A (2011), 1218 (11), 1509-1518CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
      Ultra-high-pressure liq. chromatog. (UHPLC) has great potential for the sepns. of both small mols. and polymers. However, the implementation of UHPLC for the anal. of macromols. invokes several problems. First, to provide information on the mol.-wt. distribution of a polymer, size-exclusion (SEC) columns with specific pore sizes are needed. Development of packing materials with large pore diams. and pore vols. which are mech. stable at ultra-high-pressures is a technol. challenge. Addnl., narrow-bore columns are typically used in UHPLC to minimize the problem of heat dissipation. Such columns pose stringent requirements on the extra-column dispersion, esp. for large (slowly diffusing) mols. Finally, UHPLC conditions generate high shear rates, which may affect polymer chains. The possibilities and limitations of UHPLC for size-based sepns. of polymers are addressed in the present study. We demonstrate the feasibility of conducting efficient and very fast size-based sepns. of polymers using conventional and wide-bore (4.6 mm I.D.) UHPLC columns. The wider columns allow minimization of the extra-column contribution to the obsd. peak widths down to an insignificant level. Reliable SEC sepns. of polymers with mol. wts. up to ca. 50 kDa are achieved within less than 1 min at pressures of about 66 MPa. Due to the small particles used in UHPLC it is possible to sep. high-mol.-wt. polymers (50 kDa ≤ M r ≤ 1-3 MDa, upper limit depends on the flow rate) in the hydrodynamic-chromatog. (HDC) mode. Very fast and efficient HDC sepns. are presented. For very large polymer mols. (typically larger than several MDa, depending on the flow rate) two chromatog. peaks are obsd. This is attributed to the onset of mol. deformation at high shear rates and the simultaneous actions of hydrodynamic and slalom chromatog.
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    92. 92
      Im K. Park H.-w. Lee S. Chang T. Two-dimensional liquid chromatography analysis of synthetic polymers using fast size exclusion chromatography at high column temperature J. Chromatogr. A 2009 1216 4606 4610
      92
      Two-dimensional liquid chromatography analysis of synthetic polymers using fast size exclusion chromatography at high column temperature
      Im, Kyuhyun; Park, Hae-woong; Lee, Sekyung; Chang, Taihyun
      Journal of Chromatography A (2009), 1216 (21), 4606-4610CODEN: JCRAEY; ISSN:0021-9673. (Elsevier B.V.)
      In recent years, two-dimensional liq. chromatog. (2D-LC) was used increasingly for the anal. of synthetic polymers. A 2D-LC anal. provides richer information than a single chromatog. anal. at the cost of longer anal. time. The time required for a comprehensive 2D-LC anal. is essentially proportional to the anal. time of the second dimension sepn. Many of 2D-LC analyses of synthetic polymers have employed size exclusion chromatog. (SEC) for the second-dimension anal. due to the relatively short anal. time in addn. to the wide use in the polymer anal. Nonetheless, short SEC columns are often used for 2D-LC analyses to reduce the sepn. time, which inevitably deteriorates the resoln. In this study, we demonstrated that high temp. SEC can be employed as an efficient second-LC in the 2D-LC sepn. of synthetic polymers. By virtue of high temp. operation (low solvent viscosity and high diffusivity of the polymer mols.), a normal length SEC column can be used at high flow rate with little loss in resoln.
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    93. 93
      Im K. Park H. W. Kim Y. Chung B. H. Ree M. Chang T. Comprehensive two-dimensional liquid chromatography analysis of a block copolymer Anal. Chem. 2007 79 1067 1072
      93
      Comprehensive Two-Dimensional Liquid Chromatography Analysis of a Block Copolymer
      Im, Kyuhyun; Park, Hae-Woong; Kim, Youngtak; Chung, Bonghoon; Ree, Moonhor; Chang, Taihyun
      Analytical Chemistry (2007), 79 (3), 1067-1072CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
      A two-dimensional liq. chromatog. (2D-LC) method, normal phase liq. chromatog. (NPLC) for one dimension and reversed phase liq. chromatog. (RPLC) for the other dimension, was employed to map the mol. wt. distribution (MWD) of the individual blocks of a polystyrene-block-polyisoprene (PS-b-PI) diblock copolymer. The first-dimension (1st-D) NPLC separates PS-b-PI according to the PS block length while the second-dimension (2nd-D) RPLC separates PS-b-PI according to the PI block length. For the first-dimension NPLC sepn., the column temp. was controlled to improve the resoln. while the 2nd-D RPLC was run isothermally to reduce the sepn. time. The MWD information of individual blocks provides equiv. information to MWD and chem. compn. distribution of a block copolymer. In this anal., the effluent from the 1st-D LC sepn. is concd. before the injection to the 2nd-D LC by use of a trap column, which allows an efficient interface between the two LC sepns. Over 200 different block copolymer species could be identified from the 2D-LC chromatogram.
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    94. 94
      Murphy R. E. Schure M. R. Foley J. P. One- and two dimensional chromatographic analysis of alcohol ethoxylates Anal. Chem. 1998 70 4353 4360
      94
      One- and Two-Dimensional Chromatographic Analysis of Alcohol Ethoxylates
      Murphy, Robert E.; Schure, Mark R.; Foley, Joe P.
      Analytical Chemistry (1998), 70 (20), 4353-4360CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
      Two-dimensional liq. chromatog. (2DLC) is an increasingly popular technique which has the potential to provide a far more detailed sepn. and characterization of alc. ethoxylates (AE) than was shown by previously used sepn. techniques. The AE are unique in that these mols. have distributions in both alkyl and ethylene oxide chain lengths. The single-column techniques of open-tubular SFC, normal- and reversed-phase HPLC, and the multiple column technique of 2DLC are compared in terms of the efficacy of sepn. and characterization of the alkyl and ethoxylate distributions in a select group of AE. The combination of normal- and reversed-phase HPLC in a 2DLC system accomplishes the simultaneous alkyl and ethylene oxide distribution anal. The advantage of using 2DLC over one-dimensional chromatog. techniques is clearly demonstrated in the increased selectivity resulting in the ability to produce the ethylene oxide distributions of each alkyl component in an AE. In addn., 2DLC chromatograms are easier to interpret due to ordering of the chromatograms.
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