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ArticleDecember 13, 2022

Comparison of Cyclic and Linear Poly(lactide)s Using Small-Angle Neutron Scattering
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Philip B. Yang*
Philip B. Yang
Department of Chemistry, University of Bath, Claverton Down, BathBA2 7AY, United Kingdom
*Email: [email protected]
More by Philip B. Yang
https://orcid.org/0000-0001-9191-0517
Matthew G. Davidson
Matthew G. Davidson
Institute for Sustainability and Department of Chemistry, University of Bath, Claverton Down, BathBA2 7AY, United Kingdom
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Karen J. Edler*
Karen J. Edler
Department of Chemistry, University of Bath, Claverton Down, BathBA2 7AY, United Kingdom
Centre for Analysis and Synthesis, Department of Chemistry, Lund University, SE-221 00Lund, Sweden
*Email: [email protected]
More by Karen J. Edler
https://orcid.org/0000-0001-5822-0127
Niamh Leaman
Niamh Leaman
Department of Chemistry, University of Bath, Claverton Down, BathBA2 7AY, United Kingdom
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Elly K. Bathke
Elly K. Bathke
Department of Chemistry, University of Bath, Claverton Down, BathBA2 7AY, United Kingdom
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Strachan N. McCormick
Strachan N. McCormick
Institute for Sustainability and Department of Chemistry, University of Bath, Claverton Down, BathBA2 7AY, United Kingdom
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Olga Matsarskaia
Olga Matsarskaia
Institut Laue Langevin, 71 Av. Des Martyrs, 38000Grenoble, France
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https://orcid.org/0000-0002-7293-7287
Steven Brown
Steven Brown
Scott Bader, Wollaston, WellingboroughNN29 7RJ, United Kingdom
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Macromolecules

Cite this: Macromolecules 2022, 55, 24, 11051–11058

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https://doi.org/10.1021/acs.macromol.2c02020

Published December 13, 2022

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Abstract

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Small-angle neutron scattering (SANS) experiments were conducted on cyclic and linear polymers of racemic and l-lactides (PLA) with the goal of comparing chain configurations, scaling, and effective polymer–solvent interactions of the two topologies in acetone-d₆ and THF-d₈. There are limited reports of SANS results on cyclic polymers due to the lack of substantial development in the field until recently. Now that pure, well-defined cyclic polymers are accessible, unanswered questions about their rheology and physical conformations can be better investigated. Previously reported SANS experiments have used cyclic and linear polystyrene samples; therefore, our work allowed for direct comparison using a contrasting (structurally and sterically) polymer. We compared SANS results of cyclic and linear PLA samples with various microstructures and molecular weights at two different temperatures, allowing for comparison with a wide range of variables. The results followed the trends of previous experiments, but much greater differences in the effective polymer–solvent interaction parameters between cyclic and linear forms of PLA were observed, implying that the small form factor and hydrogen bonding in PLA allowed for much more compact conformations in the cyclic form only. Also, the polymer microstructure was found to influence polymer–solvent interaction parameters substantially. These results illustrate how the difference in polymer–solvent interactions between cyclic and linear polymers can vary greatly depending on the polymer in question and the potential of neutron scattering as a tool for identification and characterization of the cyclic topology.

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Subjects

Introduction

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Cyclic polymers have been mentioned in the literature for decades, but their development has been stunted by synthetic issues and the presence of linear contaminants. (1−4) However, in the past 15 years, there have been many advances in synthetic methods, which have allowed pure (i.e., no linear contaminants detected in GPC/MALDI-TOF) cyclic polymers to be synthesized with relative ease. (5−10) Cyclic polymers often exhibit lower viscosities, higher transition temperatures, better thermal stability, and faster crystallization rates compared to conventional linear polymers due to a lack of end groups. The cyclic topology has also been shown to be advantageous in certain catalysis, thermoset adhesive, and drug delivery applications. (1,11) We have taken interest in using cyclic polymers to improve the commercial potential of bio-based and biodegradable polymers through accessing a wider range of properties.

The resurgent interest in cyclic polymers means that certain questions have yet to be fully answered, such as their rheological behavior. Specifically, the conformations that cyclic polymers adopt and how they relax stress without free end groups (see Figure 1) are not fully understood. This has been investigated via rheological studies and simulations, but there are varying conclusions, and results have been drastically influenced by linear contaminants. (12−17)

Figure 1. Cyclic and linear topologies of PLA.

Understanding the physical intricacies of these polymers will allow for better optimization and commercialization of the cyclic topology. For instance, the lack of reptation in cyclic polymers could be useful in applications such as rheology modification. (18)

Polymer–solvent interactions and other physical behaviors can be analyzed using small-angle scattering, either using X-rays (SAXS) or neutrons (SANS). It is known from experiment that the effective polymer–solvent interaction parameter (χ_eff or the Flory–Huggins parameter) is lower for a cyclic polymer compared to a corresponding linear polymer. (18) A lower χ_eff value means that the cyclic polymer effectively experiences a more favorable solvent environment. This difference can be rationalized by the smaller radius of gyration (R_g) possessed by the cyclic topology, resulting in a greater local monomer density and more favorable effects from inter/intramolecular interactions. The enthalpic penalty for solvating cyclic polymers is lower as a result. Previous studies have shown that cyclic polymers have lower θ temperatures and higher dissolution limits compared to linear polymers, which supports the idea of a better solvent environment. (19,20) The extent of the difference in χ_eff between linear and cyclic polymers is often dependent on solvent choice, as would be expected.

It is also known that ν, the Flory exponent, which describes how the radius of gyration (i.e., chain size, see eq 1) scales with the molecular weight/degree of polymerization, is slightly larger for the cyclic polymer in a near-θ solvent (ν_cyclic = 0.52/0.53 and ν_linear = 0.50), but little difference has been reported in a good solvent (near 0.58). (18,21,22)

R_{g} \propto N^{v}

(1)

Previously reported SANS studies have experimented with cyclic and linear poly(styrene)s in cyclohexane-d₁₂ at varying temperatures and solvent qualities, showing notable differences when these variables are altered. For instance, the study by Gartner et al. showed that ν for linear polymers decreased monotonically as solvent quality decreases, but this observation was only seen for cyclic polymers in good solvent regimes, while a plateau was observed at near-θ conditions. (18) However, very few cyclic and linear polymers have been compared using SANS to our knowledge. Known examples include polystyrene and poly(dimethylsiloxane) (PDMS), but they may not represent every polymer case. (18,23,24) Previous results have also been limited in terms of molecular weights or q ranges, and further study is required to fully understand how the cyclic topology behaves in SANS experiments.

Our group has synthesized cyclic polymers of racemic and l-lactides using a modified ring expansion polymerization (REP) catalyzed by a tin(II) catecholate generated in situ from tin octoate, resulting in cyclic polymers with no detectable linear contaminants. (5,25)

PLA is one of the most studied cyclic polymers partly because the linear form is the most produced bio-based and biodegradable polymer. (26) PLA has found use in biomedical and packaging applications and receives constant academic attention because the chirality of lactide allows for variation of polymer microstructures (see Figure 2), which greatly affects physical properties and the degree of crystallinity. (27,28) Importantly, PLA differs from polystyrene structurally and sterically, to the point where reported molecular weights of PLA from GPC are occasionally corrected to account for this. (29) Our polymerizations of racemic lactide and l-lactide (see Figure 3) have allowed for experimentation with microstructures, and we have synthesized heterotactically enriched PLA (P_r = 0.77). Most reported cyclic polymerizations of lactide are of the l-stereoisomer, as PLLA is the commercial form. (6,26,30−32)

Figure 2. Microstructures of PLA compared in this study with labeled stereocenters.

Figure 3. Lactide monomer/s used to synthesize PLA analyzed in this study. The racemic lactide is a 50:50 mixture of l- and d-isomers. Isotactic PLLA was made using l-lactide only. (25)

Such variation in monomer choice and microstructures (and the effects of changing these variables) is not present in polystyrene. In addition, PLA is a more polar polymer with less steric bulk, which may influence the way in which its rings interact and pack together, which would affect χ_eff and ν.

As a result (and due to often reported weak scattering for PLA samples in SAXS), (33) we report the results of SANS experiments on cyclic and linear poly(lactide) samples at a range of molecular weights, microstructures, and temperatures. This work was done with the aim to compare χ_eff, ν, and general scattering behaviors to those of previous polystyrene studies while introducing new variables. The use of REP for the synthesis also allows us to see if polymers made using this simple, low-cost approach will give reasonable scattering results, which agree with the expected trends. Successful results would be a good indicator of the synthetic progress made in the synthesis of cyclic polymers in recent years. Alternative ring closure approaches have been found to have a systematic effect on chain conformations and polymer–solvent χ_eff, but the trends between cyclic and linear topologies were largely unaffected. (18)

Materials and Methods

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Synthetic Procedures

Atactic cyclic PLA was synthesized using a tin(II) catecholate system generated in situ by the reaction of tin octoate and a catechol. Comparable linear polymers (of rac- and l-lactide) were made by replacing the coinitiator with benzyl alcohol, a common coinitiator for linear polymerizations of lactide. (34) This method was used for the majority of samples used in this study. For cyclic heterotactic PLA and PLLA samples, catalysts and protocols that will be reported elsewhere were used (manuscript in preparation). Cyclic and linear topologies were determined by comparing viscosities in Mark–Houwink plots, using MALDI-TOF and ¹H NMR to confirm a lack/presence of end groups on the polymers and by comparing glass transition temperatures (T_g’s). Cyclic polymers are known to have noticeably lower viscosities and higher transition temperatures compared to linear counterparts of similar molecular weights, and the extent of these differences is well-known for PLA in particular. (5,6) Such evidence for cyclic topology can be found in the Supporting Information. Basic characterization of samples used in this study, including molecular weights, probability of racemic enchainment (P_r), and T_g’s, can be found in Table 1.

Table 1. GPC Characterization of Poly(lactide) (PLA) Samples Measured in This Work

sample	tacticity	M_n(g mol^–1)^a	M_w(g mol^–1)	Đ	T_g (°C)	P_r
cycle C1	atactic	18,330	29,170	1.59	43.3	0.6
cycle C2	atactic	60,060	88,080	1.47	48.1	0.6
cycle C3	isotactic-PLLA	74,440	135,710	1.82	55.4	N/A^b
cycle C4	heterotactic	29,130	51,580	1.77	46.9	0.77
linear L1	atactic	19,900	33,480	1.68	42.3	0.6
linear L2	atactic	34,500	54,530	1.58	44.2	0.6
linear L3	isotactic-PLLA	38,040	45,872	1.21	47.7	N/A^b

^{^a}

Molecular weight determined by GPC relative to polystyrene standards.

^{^b}

P_r unavailable as these samples are polymers of l-lactide only (i.e., no racemic enchainment possible).

Cyclic Poly(rac-lactide)

3-Methyl catechol (0.0012 g, 0.01 mmol) was added to a dry Schlenk flask under argon before Sn(Oct)₂ (0.0041 g, 0.01 mmol) was added as a 0.01 M solution in chlorobenzene. rac-Lactide (1.4413 g, 10 mmol) was then added under a flow of argon before the closed vessel was immersed in an oil bath preheated to 160 °C for 60 min. The reaction was then stopped, and the colorless, viscous polymer was dissolved in dichloromethane before being precipitated using methanol. The precipitate was recovered and dried in vacuo to remove the residual solvent. [Monomer]:[catalyst] ratios were varied from 100:1 up to 1000:1 for all polymerizations to give polymers of varying molecular weights.

Linear Poly(lactide)

Benzyl alcohol (0.0011 g, 0.01 mmol) was added to a dry Schlenk flask under argon before Sn(Oct)₂ (0.0041 g, 0.01 mmol) was added as a 0.01 M solution in chlorobenzene. rac-Lactide (1.4413 g, 10 mmol) was then added under a flow of argon before the closed vessel was immersed in an oil bath preheated to 160 °C for 60 min. The reaction was then stopped, and the colorless, viscous polymer was dissolved in dichloromethane before being precipitated using methanol. The precipitate was recovered and dried in vacuo to remove the residual solvent.

SANS Measurements

All samples were dissolved in acetone-d₆ or THF-d₈ at 1 wt %, and scattered neutron intensities were collected. Acetone is the θ solvent for PLA and THF is considered to be a “good” solvent for PLA, commonly used for routine analysis in GPC, MALDI-TOF, etc. (6,7,30) Samples were filled into round quartz cells (“banjo”-type, Hellma, Muelheim, Germany) with a thickness of 2 mm.

SANS measurements were performed on the D11 SANS instrument at the Institut Laue Langevin (ILL), Grenoble, France with a variable temperature sample block for measurements at 15 and 40 °C. (35) The sample-to-detector distance was varied between 1.7 and 8 m for all samples to cover a range of q from 0.018 to 0.52 Å^–1. For some samples, an additional sample-to-detector distance was employed to give low q measurements down to 0.003 Å ^–1.

The scattering variable q is expressed in terms of the neutron wavelength and scattering angle (θ) as q = (4π/λ) sin(θ/2) where the neutron wavelength was λ = 6 Å with a full width at half-maximum (FWHM) wavelength spread of 9%. The data were corrected for transmission, flat field, and detector noise (the latter by a measurement of a boron carbide absorber). The scattering of the solvent was subtracted. The data were calibrated to the absolute scale by attenuated empty beam measurements. Data reduction was performed using Mantid. (36) Raw data were stored in the .nxs format. (37) Graphs of the reduced SANS data not shown in this manuscript can be found in the Supporting Information.

RPA Analysis of SANS Data

As mentioned in the paper by Gartner et al., (18) the scattering intensity predicted by the RPA for a polymer–solvent system is expressed as: (38−40)

I (q) = Δ ρ^{2} {[\frac{1}{N v_{m} ϕ_{p} P (q)} + \frac{1}{v_{s} (1 - ϕ_{p})} - \frac{2 χ_{RPA}^{eff}}{\sqrt{v_{m} v_{s}}}]}^{- 1} + B

(2)

Δρ is the difference between the scattering length densities of the polymer and the solvent, N is the polymer degree of polymerization, v_m and v_s are the volumes of the monomer and solvent particles, respectively, χ_eff is the effective Flory–Huggins parameter for the polymer–solvent system, ϕ_p is the polymer volume fraction, and B is the incoherent background.

The volume fraction ϕ_p was fitted to check the validity of the study by comparing it to the known concentration. The results were in good agreement with the expected values, taking into account acceptable error. Whether ϕ_p was fitted or not had little effect on the fitting results (see the Supporting Information for an example comparison). The form factor P(q) for chains with an excluded volume is well-known for linear polymers (see eq 3) and can be expressed in terms of the lower incomplete gamma function, γ, as (38)

P (q) = \frac{1}{v U^{1 / 2 v}} γ (\frac{1}{2 v}, U) - \frac{1}{v U^{1 / v}} γ (\frac{1}{v}, U)

(3)

where U = q²b²N^2ν/6 and b is the statistical segment length, which was a constant value in the fitting of SANS data. However, there is no analytical solution to the form factor for cyclic polymer rings, so it must be evaluated numerically (see eq 4). (40)

P (q) = 2 \int_{0}^{1} d s (1 - s) \exp [- s^{2 v} (1 - s^{2 v}) U]

(4)

The data were fitted using RPA models in SasView (version 5.04) with χ_eff, ν, and ϕ_p as floating variables. Two different RPA models were used for cyclic and linear samples (incorporating either eq 3 or 4 above) to account for the differences in the excluded volume for the two topologies, given that cyclic chains tend to swell more in solution than their linear counterparts and thus have a different form factor. These custom RPA models were kindly provided to the authors by Professor Michael J. A. Hore. Polydispersity was not accounted for in the fitting because molecular weight had only very minor effects on our fitted results, which implies that including dispersity would also have little impact. We also note that the difference in molecular weight across comparable high- and low-molecular-weight samples was substantial enough to result in no overlap in molecular size between these samples. Using identical equations to fit our data also allowed for direct comparison with the previous work on polystyrene.

Results and Discussion

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The I(q) profiles of key samples measured in these results can be seen in Figures 4 and 5. These show similar scattering to previous work on poly(styrene), (18) but there are some notable observations. Full q-range results (Figure 4) revealed a significant upturn at low q for both PLA samples of similar molecular weight, implying the presence of aggregates or bubbles in solution. Low q measurements have been reported on cyclic poly(styrene) samples before but have not been compared directly to linear counterparts of the same molecular weight to our knowledge. (22) For samples with a low q upturn, the q range < 0.018 Å^–1 was excluded from fitting.

Figure 4. I(q) vs q plot of cyclic and linear poly(lactic acid) (PLA) samples over the full q range of 0.003 to 0.52 Å ^–1.

Figure 5. I(q) vs q plots of cyclic (top, red) and linear (bottom, blue) PLA samples (C1 and L1 in Table 1) in acetone-d₆ and THF-d₈ at 15 and 40 °C.

The temperature comparisons of cyclic and linear PLA samples (see Figure 5) showed that the cyclic sample was noticeably more affected by a change in temperature compared to the linear counterpart. This effect was especially distinct in the good solvent (THF-d₈) and suggested that there were interactions between monomers at higher temperatures in cyclic PLA only, potentially influenced by the smaller radius of gyration of the cyclic topology. This could also be evidence of the polymer collapsing in solution sufficiently that it appears as a particle to the SANS instrument. The glass transition temperature of these samples ranged between 47 and 57 °C (see Table S1), but proximity to this temperature would not be expected to affect the behavior of the polymers in solution. The previous study by Gartner et al. reported variation in the scattering data for polystyrene at different temperatures but to a much lesser extent. (18) This was rationalized by the formation of bubbles in the cell at temperatures close to the boiling point of the solvent. This has likely influenced the low q results in Figures 4 and 5, but the more substantial differences at high q, seen for the cyclic samples only, are not fully understood. When the data for the high-temperature sample in Figure 5b was fitted, the q range was restricted to exclude the upturn at high q (i.e., q > 0.3 Å^–1 was excluded), and these data gave no anomalous fitted values.

Fitted values of χ_eff and ν for poly(lactide) samples showed expected trends (i.e., lower χ_eff and higher ν for the cyclic polymer samples), but there was a much greater difference in χ_eff values between the two topologies (see Figure 6). The average χ_eff value for the cyclic PLA samples varied between 0.23 and 0.35, whereas the range was 0.40–0.51 for corresponding linear polymers. While it was expected that the cycles would have lower χ_eff values, these results show differences far greater than previously reported. (18) The ratio ⟨R_g, cyclic²⟩/⟨R_g, linear²⟩ for these samples was 0.841 ± 0.010, which illustrated a smaller radius of gyration for the cyclic topology as expected. Due to the easier packing and capability of hydrogen bonding, cyclic PLA may possess a higher local monomer density, and the intermolecular interactions between monomers would likely be more substantial in PLA than in polystyrene. PLA may be able to make better use of the smaller radius of gyration of the cyclic topology and further improve the solvent environment compared to linear counterparts. While there are sigma–pi interactions between chains in polystyrene, the magnitudes of the interactions between the two polymers are very different. While polymers with molecular weights ranging from 18,330 to 74,441 g mol^–1 were analyzed, there was a minimal difference in the scattering profiles and fitted values of these polymers (as can be seen in Figure 6). This is in agreement with other SANS results, which have reported modest dependence of χ_eff on the molecular weight. (41)

Figure 6. Graphs of χ_eff of PLA samples measured in this study at 15 and 40 °C in acetone-d₆ and THF-d₈. Textured bars denote different samples of the same topology as described in the legend. These data can also be seen as a graph of χ_eff vs 1/T in the Supporting Information (Figure S7).

There was more variation in ν values for these polymers compared to the literature, (18) although not to the same extent as for the χ_eff values (see Figure 7). The expected trend of a higher Flory exponent for the cyclic polymer was maintained here, while linear samples of poly(lactic acid) were more affected by solvent choice compared to cyclic counterparts.

Figure 7. Graphs of ν against 1/T (Kelvin) for cyclic and linear PLA (left) samples. Textured bars denote different samples of the same topology as described in the legend. These data can also be seen as a graph of ν vs 1/T in the Supporting Information (Figure S8).

Figure 8 shows a comparison of χ_eff values between cyclic and linear PLA samples of differing microstructures, acquired by averaging fitted χ_eff values for atactic PLA samples (seen already in Figure 6), heterotactic PLA samples, and isotactic PLLA samples. This average includes polymers of varying molecular weights because this was shown to have a minimal impact on χ_eff values in both our and previously reported results, (41) including all polymers allowed for more data to compare. While a minimal difference was seen in the linear polymers, there was substantial variation in cyclic PLA values, with χ_eff decreasing as the microstructure changed from heterotactic to atactic to isotactic PLLA (see Figure 8).

Figure 8. Charts showing variation in average χ_eff of cyclic (red) and linear (blue) PLA samples of different microstructures illustrated previously in Figure 2.

This variation in χ_eff across polymers of the same monomer is substantial but is not surprising given how the microstructure influences properties in PLA. A possible explanation for this may be related to the ability of the polymer chains in the different samples to pack together in the solid form. Isotactic PLLA is crystalline, with methyl groups facing the same direction allowing for close packing in a tight crystalline structure. This is well-evidenced by reported crystal structures of PLLA and the known amorphous nature of atactic and heterotactic PLA forms. (42,43) While there are differences between packing in a crystalline phase and in solution, the behavior in solution would be expected to be influenced by differences in the crystalline phase across different forms of PLA. Any difference in the interactions between polymer chains in solution would result in a difference in local monomer density and χ_eff values as a result.

In contrast, heterotactic PLA is amorphous as a solid and would therefore likely also arrange less efficiently in solution, leading to fewer intrachain contacts, which would raise χ_eff. The notable effect of the microstructure on the polymer–solvent interactions in the cyclic samples specifically can be rationalized by the smaller R_g of the cyclic topology. The increased local monomer density and intrachain contacts of the cyclic topology would lower the χ_eff more compared to linear counterparts but also result in a greater influence of the polymer microstructure on these results (i.e., as there are more interactions to influence). The positions of these methyl groups may also influence threading, folding, and knotting of cyclic polymers to a greater extent than in linear counterparts.

To our knowledge, there are limited reports of comparisons of χ_eff for linear PLA samples of differing microstructures, but it is known that amorphous PLDA (i.e., atactic or heterotactic) will exhibit a notably higher χ_eff value compared to crystalline isotactic PLLA (although this was not derived by SANS). (44) In our case, we see this trend followed for the cyclic samples only, but it is still rational that the amorphous PLA would show a higher χ_eff. Asymmetries in chain conformations among chemically similar copolymers can be known to result in relatively high χ_eff values due to the introduction of enthalpic and entropic contributions. (45) The asymmetry in the atactic and heterotactic PLA samples could have contributed to higher χ_eff parameters.

Error in χ_eff and ν values was tested by setting the values of χ_eff and ν to different starting values: 0.25, 0.5, and 0.75 before fitting the data using the custom RPA models, which resulted in zero variation in the final fitted values. As a result, the error bars in Figures 6 and 7 were plotted using the error in the calculation reported by SasView. In the case of Figure 8, the standard deviation of χ_eff values was used to obtain error bars in all cases aside from isotactic PLLA samples (due to only one sample being measured, the error for this was taken from the error in the fitting of the data).

Conclusions

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We have demonstrated how SANS experiments on cyclic and linear polymers can be drastically influenced by polymer choice, microstructure, temperature, and solvent choice. The previously established trends in polymer–solvent interactions and the Flory exponent between the two topologies have been observed in our results. However, the extent of the difference in χ_eff between cyclic and linear poly(lactic acid) (PLA) samples was much more substantial compared to the literature on polystyrene, which illustrated how intermolecular forces and steric bulk could play a large role in the polymer–solvent interactions in cyclic polymers specifically.

Scattering profiles of I(q) vs q were comparable to the literature, but significant temperature variation at high q was observed in PLA. The study of atactic, heterotactic, and isotactic PLLA revealed substantial differences in χ_eff values, highlighting the extent to which cyclic PLA in particular was affected by monomer choice and microstructures, even though lactide monomers vary only in the orientation of the methyl groups.

These results highlight the value of SANS experiments in comparing cyclic and linear polymers, as well as the need to compare novel polymers such as PLA to access new variables that have not been tested before to our knowledge. Such analysis may give a better idea of the conformations and physical behavior of cyclic polymers, as well as how best to use these properties to develop cyclic polymers for specific applications as they garner increasing interest. In addition, these results highlight the potential of neutron scattering as a tool for identification and characterization of the cyclic topology.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.macromol.2c02020.

Information about materials and methods used to synthesize the polymers analyzed in this work, as well as characterization data for the cyclic and linear polymers (such as MALDI-TOF spectra); further data from SANS experiments, such as some intensity vs q plots not included in this manuscript and R_g values for key samples (PDF)

ma2c02020_si_001.pdf (493.94 kb)

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Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

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Corresponding Authors
- Philip B. Yang - Department of Chemistry and , University of Bath, Claverton Down, BathBA2 7AY, United Kingdom; https://orcid.org/0000-0001-9191-0517; Email: [email protected]
- Karen J. Edler - Department of Chemistry and , University of Bath, Claverton Down, BathBA2 7AY, United Kingdom; Centre for Analysis and Synthesis, Department of Chemistry, Lund University, SE-221 00Lund, Sweden; https://orcid.org/0000-0001-5822-0127; Email: [email protected]
Authors
- Matthew G. Davidson - Institute for Sustainability and Department of Chemistry and , University of Bath, Claverton Down, BathBA2 7AY, United Kingdom
- Niamh Leaman - Department of Chemistry and , University of Bath, Claverton Down, BathBA2 7AY, United Kingdom
- Elly K. Bathke - Department of Chemistry and , University of Bath, Claverton Down, BathBA2 7AY, United Kingdom
- Strachan N. McCormick - Institute for Sustainability and Department of Chemistry and , University of Bath, Claverton Down, BathBA2 7AY, United Kingdom
- Olga Matsarskaia - Institut Laue Langevin, 71 Av. Des Martyrs, 38000Grenoble, France; https://orcid.org/0000-0002-7293-7287
- Steven Brown - Scott Bader, Wollaston, WellingboroughNN29 7RJ, United Kingdom
Notes
The authors declare no competing financial interest.

Acknowledgments

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We would like to acknowledge the University of Bath, the Centre for Sustainable and Circular Technologies (CSCT), and Scott Bader for their support to P.B.Y. in his PhD studies. We would also like to acknowledge the CSCT, funded by the EPSRC (EP/L016354/1) for PhD support to P.B.Y., N.L., and E.K.B. We thank ILL for the award of beamtime to conduct these experiments under experiment number 9-11-2065 (doi:10.5291/ILL-DATA.9-11-2065) and Professor Michael J. A. Hore (Case Western Reserve University, Cleveland, Ohio 44106, United States) for his assistance with the RPA model for fitting this data. This work benefited from the use of the SasView application, originally developed under NSF award DMR-0520547. SasView contains code developed with funding from the European Union’s Horizon 2020 research and innovation program under the SINE2020 project, grant agreement no. 654000. The data for these experiments are freely available on the University of Bath Research Data Archive (https://doi.org/10.15125/BATH-01203).

References

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This article references 45 other publications.

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Yang, Philip B.; Davidson, Matthew G.; Edler, Karen J.; Brown, Steven
Biomacromolecules (2021), 22 (9), 3649-3667CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
A review. Cyclic polymers have long been reported in the literature, but their development has often been stunted by synthetic difficulties such as the presence of linear contaminants. Research into the synthesis of these polymers has made great progress in the past decade, and this review covers the synthesis, properties, and applications of cyclic polymers, with an emphasis on bio-based aliph. polyesters. Synthetic routes to cyclic polymers synthesized from bioderived monomers, alongside mechanistic descriptions for both ring closure and ring expansion polymn. approaches, are reviewed. The review also highlights some of the unique phys. properties of cyclic polymers together with potential applications. The findings illustrate the substantial recent developments made in the syntheses of cyclic polymers, as well as the progress which can be made in the commercialization of bio-based polymers through the versatility this topol. provides.
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Haque, F. M.; Grayson, S. M. The Synthesis, Properties and Potential Applications of Cyclic Polymers. Nat. Chem. 2020, 12, 433– 444, DOI: 10.1038/s41557-020-0440-5
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The synthesis, properties and potential applications of cyclic polymers
Haque, Farihah M.; Grayson, Scott M.
Nature Chemistry (2020), 12 (5), 433-444CODEN: NCAHBB; ISSN:1755-4330. (Nature Research)
A review. Unlike their more common linear counterparts, cyclic polymers have a ring-like structure and a lack of chain ends. Because of their topol., cyclic polymers exhibit a unique set of properties when compared with linear or branched macromols. For example, cyclic homopolymers exhibit a reduced hydrodynamic vol. and a slower degrdn. profile compared with their linear analogs. Cyclic block copolymers self-assemble into compact nanostructures, as illustrated by their reduced domain spacing when cast into thin films and their reduced micellar size in soln. Although methods for prepg. well-defined cyclic polymers have only been available since 1980, the extensive utilization of the cyclic topol. in nature highlights the vital role that a cyclic architecture can play in imparting valuable phys. properties, such as increased chem. stability or propensity towards self-assembly. This Review describes the major developments in the synthesis of cyclic polymers and provides an overview of their fundamental phys. properties. In this context, preliminary studies exploring potential applications will be critically assessed and the remaining challenges for the field delineated.
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Chang, Y. A.; Waymouth, R. M. Recent Progress on the Synthesis of Cyclic Polymers via Ring-Expansion Strategies. J. Polym. Sci. Part A: Polym. Chem. 2017, 55, 2892– 2902, DOI: 10.1002/pola.28635
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Recent progress on the synthesis of cyclic polymers via ring-expansion strategies
Chang, Young A.; Waymouth, Robert M.
Journal of Polymer Science, Part A: Polymer Chemistry (2017), 55 (18), 2892-2902CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)
A review. Cyclic polymers are the simplest topol. isomers of linear macromols., but exhibit properties that differ from linear chains in ways that remain imperfectly understood. The difficulty of synthesizing appropriately pure and high mol. wt. cyclic samples has hindered exptl. studies. Ring-closure methods, while versatile, are inherently limited in the range of mol. wts. that can be achieved. Ring-expansion methods are a much more promising strategy toward obtaining high mol. wt. cyclic polymers. The current review focuses on recent developments in ring-expansion polymn. strategies toward the synthesis of high mol. wt. cyclic polymers. Significant progress in the last decade has made the synthesis of cyclic polymers possible by a variety of methods, such as ruthenium- and tungsten-catalyzed ring-expansion metathesis polymn., organocatalytic and Lewis acid-catalyzed zwitterionic polymn., RAFT and nitroxide-mediated radical polymn., among many others. While the study of cyclic polymers has long been hampered by synthetic challenges, the recent resurgence of interest in this field presents an exciting opportunity for chemists. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.
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Kricheldorf, H. R.; Lee, S. R. Polylactones. 35. Macrocyclic and Stereoselective Polymerization of β-D,L-Butyrolactone with Cyclic Dibutyltin Initiators. Macromolecules 1995, 28, 6718– 6725, DOI: 10.1021/ma00124a004
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Polylactones. 35. Macrocyclic and Stereoselective Polymerization of β-D,L-Butyrolactone with Cyclic Dibutyltin Initiators
Kricheldorf, Hans R.; Lee, Soo-Ran
Macromolecules (1995), 28 (20), 6718-25CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
2,2-Dibutyl-1,3-dioxa-2-stannanes prepd. from dibutyltin oxide and 1,3-propanediol or neopentanediol were used as cyclic initiators for polymns. of β-D,L-butyrolactone. Because these initiators were not reactive below 50 °C, all polymns. were conducted in bulk at temps. ≥50 °C. As evidenced by 13C NMR spectroscopy, the resulting poly(D,L-butyrolactone) is preferentially syndiotactic, but the percentage of syndiotactic diads decreases with increasing reaction temp. 1H NMR spectra proved that the insertion of lactones occurred at both Sn-O bonds of the cyclic initiators, and thus, the propagation yields automatically macrocyclic esters. The ring size increases with increasing monomer/initiator ratio and higher conversions. Selective ring opening with 1,2-dimercaptoethane produces linear polyesters with shorter elution times in GPC measurements than the corresponding macrocycles of the same mol. wt. Batchwise copolymns. with ε-caprolactone yielded macrocyclic block copolyesters which after ring-opening with dimercaptoethane turned into linear A-B-A triblock copolymers. However, when mixts. of both lactones were copolymd. at 100 °C, random copolyesters were obtained.
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Kricheldorf, H. R.; Weidner, S. M. SnOct2-Catalyzed Syntheses of Cyclic Poly(l-Lactide)s with Catechol as Low-Toxic Co-Catalyst. J. Polym. Environ. 2019, 27, 2697– 2706, DOI: 10.1007/s10924-019-01545-5
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SnOct2-Catalyzed Syntheses of Cyclic Poly(L-lactide)s with Catechol as Low-Toxic Co-catalyst
Kricheldorf, Hans R.; Weidner, Steffen M.
Journal of Polymers and the Environment (2019), 27 (12), 2697-2706CODEN: JPENFW; ISSN:1572-8919. (Springer)
Polymns. of L-lactide in bulk at 160 or 180°C were performed with 1/1 mixts. of catechol (CA) or 4-tert-butylcatechol (BuCA) and tin(II)-2-ethylhexanoate (SnOct2) as catalysts and a variation of the Lac/Cat ratio. Wt. av. molar masses (Mw) up to 170,000 g mol-1 were obtained with CA and up to 120,000 g mol-1 with BuCA. The cyclic structure of the resulting poly(L-lactide)s was proven by MALDI-TOF mass spectrometry and by comparison of their hydrodynamic vols. with those of com. linear poly(L-lactide)s. The predominance of even-numbered cycles increased with lower temps. and shorter polymn. times. This finding indicates that the cyclic architecture is the results of a ring-expansion polymn. mechanism. Addn. of silylated BuCA as co-catalyst was less favorable than addn. of free BuCA.
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Culkin, D. A.; Jeong, W.; Csihony, S.; Gomez, E. D.; Balsara, N. P.; Hedrick, J. L.; Waymouth, R. M. Zwitterionic Polymerization of Lactide to Cyclic Poly(Lactide) by Using N-Heterocyclic Carbene Organocatalysts. Angew. Chem., Int. Ed. 2007, 46, 2627– 2630, DOI: 10.1002/anie.200604740
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Zwitterionic polymerization of lactide to cyclic poly(lactide) by using N-heterocyclic carbene organo-catalysts
Culkin, Darcy A.; Jeong, Wonhee; Csihony, Szilard; Gomez, Enrique D.; Balsara, Nitash P.; Hedrick, James L.; Waymouth, Robert M.
Angewandte Chemie, International Edition (2007), 46 (15), 2627-2630CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
Closing the loop: The zwitterionic ring-opening polymn. of lactide in the presence of N-heterocyclic carbenes generates well-defined cyclic poly(lactide)(see scheme). The polymn. is rapid and produces macrocyclic polymers with high purity and exceptional control of mol. wt. and polydispersity.
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Kerr, R. W. F.; Ewing, P. M. D. A.; Raman, S. K.; Smith, A. D.; Williams, C. K.; Arnold, P. L. Ultrarapid Cerium(III)-NHC Catalysts for High Molar Mass Cyclic Polylactide. ACS Catal. 2021, 11, 1563– 1569, DOI: 10.1021/acscatal.0c04858
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Ultrarapid Cerium(III)-NHC Catalysts for High Molar Mass Cyclic Polylactide
Kerr, Ryan W. F.; Ewing, Paul M. D. A.; Raman, Sumesh K.; Smith, Andrew D.; Williams, Charlotte K.; Arnold, Polly L.
ACS Catalysis (2021), 11 (3), 1563-1569CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
Cyclic polyesters could improve the properties of degradable plastics, but routes to them that provide a product with faster rates, higher molar mass, and greater selectivity for cyclic vs. linear polymer are needed. Here, homogeneous Ce(III)-N-heterocyclic carbene (NHC) catalysts show outstanding activities (turn-over-frequency (TOF) > 864 000 h-1), excellent control, and selectivity for cyclic polylactide (PLA) topol. (>95%), yielding high molar mass PLA (60 < Mn < 250 kg mol-1). They efficiently produce cyclic PLA from rac-lactide or L-lactide and aliph. cyclic polyesters from ε-caprolactone or β-butyrolactone. The enhanced performances are only achievable from combining cooperative Lewis acidic cerium(III) and hemilabile N-heterocyclic carbene functionalities.
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Hong, M.; Chen, E. Y. X. Completely Recyclable Biopolymers with Linear and Cyclic Topologies via Ring-Opening Polymerization of γ-Butyrolactone. Nat. Chem. 2016, 8, 42– 49, DOI: 10.1038/nchem.2391
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Completely recyclable biopolymers with linear and cyclic topologies via ring-opening polymerization of γ-butyrolactone
Hong, Miao; Chen, Eugene Y.-X.
Nature Chemistry (2016), 8 (1), 42-49CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
Ring-opening polymn. (ROP) is a powerful synthetic methodol. for the chem. synthesis of technol. important biodegradable aliph. polyesters from cyclic esters or lactones. However, the bioderived five-membered γ-butyrolactone (γ-BL) is commonly referred as 'non-polymerizable' because of its low strain energy. The chem. synthesis of poly(γ-butyrolactone) (PγBL) through the ROP process has been realized only under ultrahigh pressure (20,000 atm, 160 °C) and only produces oligomers. Here we report that the ROP of γ-BL can, with a suitable catalyst, proceed smoothly to high conversions (90%) under ambient pressure to produce PγBL materials with a no.-av. mol. wt. up to 30 kg mol-1 and with controlled linear and/or cyclic topologies. Remarkably, both linear and cyclic PγBLs can be recycled back into the monomer in quant. yield by simply heating the bulk materials at 220 °C (linear polymer) or 300 °C (cyclic polymer) for one hour, which thereby demonstrates the complete recyclability of PγBL.
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Hammami, N.; Majdoub, M.; Habas, J. P. Structure-Properties Relationships in Isosorbide-Based Polyacetals: Influence of Linear or Cyclic Architecture on Polymer Physicochemical Properties. Eur. Polym. J. 2017, 93, 795– 804, DOI: 10.1016/j.eurpolymj.2017.03.050
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Structure-properties relationships in isosorbide-based polyacetals: Influence of linear or cyclic architecture on polymer physicochemical properties
Hammami, Nadia; Majdoub, Mustapha; Habas, Jean-Pierre
European Polymer Journal (2017), 93 (), 795-804CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Ltd.)
A linear biobased polyacetal was prepd. from the reaction between isosorbide and methylene chloride according a one step procedure. Cyclic polyacetal was obtained using the previous linear polymer as precursor. The resp. architectures of both polymers and their chem. compns. were carefully established using 1H NMR and MALDI-TOF spectroscopies. Their mol. wt. characteristics were defined using a triple detection size exclusion chromatog. while their thermal characteristics were investigated by the conduction of calorimetric and thermogravimetric expts. The registering of the thermomech. properties of each kind of isosorbide-based polyacetal showed that the cyclic polymer was the only one able to show a rubbery plateau. This peculiarity was justified by calcn. of the threshold value above which entanglements were possible.
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Kricheldorf, H. R.; Weidner, S. M.; Scheliga, F. Synthesis of Cyclic Poly(l-Lactide) Catalyzed by Bismuth Salicylates─A Combination of Two Drugs. J. Polym. Sci. Part A: Polym. Chem. 2019, 57, 2056– 2063, DOI: 10.1002/pola.29473
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Synthesis of cyclic poly(L-lactide) catalyzed by Bismuth Salicylates-A combination of two drugs
Kricheldorf, Hans R.; Weidner, Steffen M.; Scheliga, Felix
Journal of Polymer Science, Part A: Polymer Chemistry (2019), 57 (19), 2056-2063CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)
L-lactide was polymd. in bulk at 160 or 180°C with mixts. of bismuth subsalicylate (BiSub) and salicylic (SA) as catalysts. The SA/Bi ratio and the monomer/Bi ratio were varied. The highest mol. wts. (wt. av., Mw) were achieved at a SA/Bi ratio of 1/1 (Mw up to 92 000 g mol-1). L-Lactide was also polymd. with combinations of BiSub and silylated SA, and Mw values up to 120 000 g mol-1 were achieved at 180°C. MALDI-TOF mass spectrometry and Mark-Houwink-Sakurada measurements proved that under optimized reaction conditions the resulting polylactides consist of cycles.
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Tu, X. Y.; Liu, M. Z.; Wei, H. Recent Progress on Cyclic Polymers: Synthesis, Bioproperties, and Biomedical Applications. J. Polym. Sci. Part A: Polym. Chem. 2016, 54, 1447– 1458, DOI: 10.1002/pola.28051
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Recent progress on cyclic polymers: Synthesis, bioproperties, and biomedical applications
Tu, Xiao-Yan; Liu, Ming-Zhu; Wei, Hua
Journal of Polymer Science, Part A: Polymer Chemistry (2016), 54 (11), 1447-1458CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)
A review. Polymer topologies exert a significant effect on its properties, and polymer nanostructures with advanced architectures, such as cyclic polymers, star-shaped polymers, and hyperbranched polymers, are a promising class of materials with advantages over conventional linear counterparts. Cyclic polymers, due to the lack of polymer chain ends, have displayed intriguing phys. and chem. properties. Such uniqueness has drawn considerable attention over the past decade. The current review focuses on the recent progress in the design and development of cyclic polymer with an emphasis on its synthesis and bio-related properties and applications. Two primary synthetic strategies towards cyclic polymers, i.e., ring-expansion polymn. and ring-closure reaction are summarized. The bioproperties and biomedical applications of cyclic polymers are then highlighted. In the end, the future directions of this rapidly developing research field are discussed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016.
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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, DOI: 10.1038/nmat2292
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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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Halverson, J. D.; Lee, W. B.; Grest, G. S.; Grosberg, A. Y.; Kremer, K. Molecular Dynamics Simulation Study of Nonconcatenated Ring Polymers in a Melt. I. Statics. J. Chem. Phys. 2011, 134, 15, DOI: 10.1063/1.3587137
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Doi, Y.; Matsubara, K.; Ohta, Y.; Nakano, T.; Kawaguchi, D.; Takahashi, Y.; Takano, A.; Matsushita, Y. Melt Rheology of Ring Polystyrenes with Ultrahigh Purity. Macromolecules 2015, 48, 3140– 3147, DOI: 10.1021/acs.macromol.5b00076
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Melt Rheology of Ring Polystyrenes with Ultrahigh Purity
Doi, Yuya; Matsubara, Kazuki; Ohta, Yutaka; Nakano, Tomohiro; Kawaguchi, Daisuke; Takahashi, Yoshiaki; Takano, Atsushi; Matsushita, Yushu
Macromolecules (Washington, DC, United States) (2015), 48 (9), 3140-3147CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
The melt rheol. of highly-purified ring polystyrenes in a wide range of mol. wts. (10K ≤ Mw ≤ 240K g/mol) was investigated. All the rings revealed no obvious rubbery plateau and faster terminal relaxation compared to the linear counterparts. The rheol. data obtained were compared with some theor. models such as the Rouse ring model and the lattice-animal model. Moreover, two rheol. parameters, zero-shear viscosities η0 and the steady-state recoverable compliances Je, were estd., and their Mw dependence was discussed. From these data anal., it was found that relaxation mechanisms of ring chains can be divided into three categories depending on their Mw as follows: (1) Smaller rings (Mw ≤ 20K) exhibit faster terminal relaxation than the predicted Rouse rings. This behavior is related to the difference of the local chain conformation from linear chains. (2) Rings with the moderate mol. wt. (40K ≤ Mw ≤ 90K) exhibit dynamic moduli similar to the Rouse ring prediction. (3) A larger ring (Mw > 90K) also shows deviant behavior from the Rouse chain because its relaxation time is much longer than the Rouse ring prediction and also the lattice-animal model, where some intermol. interactions are considered to occur.
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Pasquino, R.; Vasilakopoulos, T. C.; Jeong, Y. C.; Lee, H.; Rogers, S.; Sakellariou, G.; Allgaier, J.; Takano, A.; Brás, A. R.; Chang, T.; Gooßen, S.; Pyckhout-Hintzen, W.; Wischnewski, A.; Hadjichristidis, N.; Richter, D.; Rubinstein, M.; Vlassopoulos, D. Viscosity of Ring Polymer Melts. ACS Macro Lett. 2013, 2, 874– 878, DOI: 10.1021/mz400344e
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Viscosity of Ring Polymer Melts
Pasquino, Rossana; Vasilakopoulos, Thodoris C.; Jeong, Youn Cheol; Lee, Hyojoon; Rogers, Simon; Sakellariou, George; Allgaier, Jurgen; Takano, Atsushi; Bras, Ana R.; Chang, Taihyun; Goossen, Sebastian; Pyckhout-Hintzen, Wim; Wischnewski, Andreas; Hadjichristidis, Nikos; Richter, Dieter; Rubinstein, Michael; Vlassopoulos, Dimitris
ACS Macro Letters (2013), 2 (10), 874-878CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
We have measured the linear rheol. of critically purified ring polyisoprenes, polystyrenes, and polyethylene oxides of different molar masses. The ratio of the zero-shear viscosities of linear polymer melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed as a function of the no. of entanglements Z. In the unentangled regime η0,linear/η0,ring is virtually const., consistent with the earlier data, atomistic simulations, and the theor. expectation η0,linear/η0,ring = 2. In the entanglement regime, the Z-dependence of ring viscosity is much weaker than that of linear polymers, in qual. agreement with predictions from scaling theory and simulations. The power-law extd. from the available exptl. data in the rather limited range 1 < Z < 20, η0,linear/η0,ring ∼ Z1.2±0.3, is weaker than the scaling prediction (η0,linear/η0,ring ∼ Z1.6±0.3) and the simulations (η0,linear/η0,ring ∼ Z2.0±0.3). Nevertheless, the present collection of state-of-the-art exptl. data unambiguously demonstrates that rings exhibit a universal trend clearly departing from that of their linear counterparts, and hence it represents a major step toward resolving a 30-yr-old problem.
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Gooßen, S.; Brás, A. R.; Krutyeva, M.; Sharp, M.; Falus, P.; Feoktystov, A.; Gasser, U.; Pyckhout-Hintzen, W.; Wischnewski, A.; Richter, D. Molecular Scale Dynamics of Large Ring Polymers. Phys. Rev. Lett. 2014, 113, 1– 5, DOI: 10.1103/PhysRevLett.113.168302
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Yan, Z. C.; Costanzo, S.; Jeong, Y.; Chang, T.; Vlassopoulos, D. Linear and Nonlinear Shear Rheology of a Marginally Entangled Ring Polymer. Macromolecules 2016, 49, 1444– 1453, DOI: 10.1021/acs.macromol.5b02651
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Linear and Nonlinear Shear Rheology of a Marginally Entangled Ring Polymer
Yan, Zhi-Chao; Costanzo, Salvatore; Jeong, Youncheol; Chang, Taihyun; Vlassopoulos, Dimitris
Macromolecules (Washington, DC, United States) (2016), 49 (4), 1444-1453CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
We present systematic, unique linear and nonlinear shear rheol. data of an exptl. pure ring polystyrene and its linear precursor. This polymer was synthesized anionically and characterized by interaction chromatog. and fractionation at the crit. condition. Its wt.-av. molar mass is 84 kg/mol; i.e., it is marginally entangled (entanglement no. Z ≈ 5). Its linear viscoelastic response appears to be better described by the Rouse model (accounting for ring closure) rather than the lattice-animal-based model, suggesting a transition from unentangled to entangled ring dynamics. The failure of both models in the terminal region may reflect the remaining unlinked linear contaminants and/or ring-ring interpenetration. The viscosity evolution at different shear rates was measured using a homemade cone-partitioned plate fixture in order to avoid edge fracture instabilities. Our findings suggest that rings are much less shear thinning compared to their linear counterparts, whereas both obey the Cox-Merz rule. The shear stress (or viscosity) overshoot is much weaker for rings compared to linear chains, pointing to the fact that their effective deformation is smaller. Finally, step strain expts. indicate that the damping function data of ring polymers clearly depart from the Doi-Edwards prediction for entangled linear chains, exhibiting a weak thinning response. These findings indicate that these marginally entangled rings behave like effectively unentangled chains with finite extensibility and deform much less in shear flow compared to linear polymers. They can serve as guideline for further investigation of the nonlinear dynamics of ring polymers and the development of constitutive equations.
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Gartner, T. E.; Haque, F. M.; Gomi, A. M.; Grayson, S. M.; Hore, M. J. A.; Jayaraman, A. Scaling Exponent and Effective Interactions in Linear and Cyclic Polymer Solutions: Theory, Simulations, and Experiments. Macromolecules 2019, 52, 4579– 4589, DOI: 10.1021/acs.macromol.9b00600
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Scaling Exponent and Effective Interactions in Linear and Cyclic Polymer Solutions: Theory, Simulations, and Experiments
Gartner, Thomas E., III; Haque, Farihah M.; Gomi, Aila M.; Grayson, Scott M.; Hore, Michael J. A.; Jayaraman, Arthi
Macromolecules (Washington, DC, United States) (2019), 52 (12), 4579-4589CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
Cyclic polymers have garnered increasing attention in the materials community as lack of free-chain ends in cyclic polymers results in significant differences in structure, thermodn., and dynamics compared to their linear counterparts. Yet, key open questions remain about how cyclic polymer chain conformations and effective interactions in soln. change as a function of solvent quality, ring closure chem., and the presence/absence of common synthetic impurities. We use coarse-grained mol. dynamics simulations, polymer ref. interaction site model theory, and small-angle neutron-scattering expts. on polystyrene in d-cyclohexane to demonstrate how linear and cyclic polymer chain configurations, scaling, and effective interactions are influenced by solvent quality and polymer concn. We find that the balance between the available intra- vs. interchain contacts in soln. dictate the trends in cyclic polymer size scaling and effective polymer-solvent and polymer-polymer interactions; these results are largely insensitive to the ring closure chem. and the presence of linear or cyclic dimer impurities. This study provides the broader polymer science and engineering community fundamental insights into how synthesis, purifn., and assembly of cyclic polymers in solvent(s) impact the resulting chain structure and polymer soln. thermodn.
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Suzuki, J.; Takano, A.; Matsushita, Y. The Theta-Temperature Depression Caused by Topological Effect in Ring Polymers Studied by Monte Carlo Simulation. J. Chem. Phys. 2011, 135, 204903, DOI: 10.1063/1.3663383
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The theta-temperature depression caused by topological effect in ring polymers studied by Monte Carlo simulation
Suzuki, Jiro; Takano, Atsushi; Matsushita, Yushu
Journal of Chemical Physics (2011), 135 (20), 204903/1-204903/6CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
We studied equil. conformations of linear and ring polymers in dil. solns. over the wide range of segment no. N of up to 2048 with Monte Carlo simulation, and evaluated N dependence of the radii of gyration, Rg, of chains. The polymer mols. treated in this study are assumed to be composed of beads and bonds, and they are put in a three-dimensional face-centered cubic (FCC) lattice. The values of Flory's crit. exponent, ν, for linear and ring polymers were estd. from the N dependence of Rg, and the temps. at which ν reach 1/2 were obtained. Here we define those as Θ-temps. in this report. The simulation result shows that the Θ-temp. for ring polymers is evidently lower than that of the linear polymers, and the origin of the Θ-temp. depression is discussed. Since Rg of a ring polymer is smaller than that for a linear polymer at the same N and temp., the segment d. for a ring polymer is increased by the topol. effect and the repulsive force between segments of a ring polymer at the Θ-temp. for a linear polymer is stronger. Thus, the origin of the Θ-temp. depression for ring polymers is the repulsive force emphasized by the topol. effect of rings. (c) 2011 American Institute of Physics.
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Takano, A.; Kushida, Y.; Ohta, Y.; Masuoka, K.; Matsushita, Y. The Second Virial Coefficients of Highly-Purified Ring Polystyrenes in Cyclohexane. Polymer 2009, 50, 1300– 1303, DOI: 10.1016/j.polymer.2009.01.019
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The second virial coefficients of highly-purified ring polystyrenes in cyclohexane
Takano, Atsushi; Kushida, Yuuki; Ohta, Yutaka; Masuoka, Keisuke; Matsushita, Yushu
Polymer (2009), 50 (5), 1300-1303CODEN: POLMAG; ISSN:0032-3861. (Elsevier Ltd.)
The second virial coeffs. A 2 of ring polystyrenes with high purity in cyclohexane were measured by light scattering in the temp. range 27.0-34.5 °C. The purity of four samples with M w of 16k, 42k, 110k and 570k was detd. to be all over 96% by HPLC. It has been found that A 2s of all the samples are definitely pos. at the theta temp. of linear polystyrene, 34.5 °C, and the measured values for four samples converged to zero at 27.7 °C with decreasing temp. This value is below the previously reported one, but it is quite consistent with the predicted value based on the topol. repulsive interaction among the ring polymer mols.
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Takano, A.; Ohta, Y.; Masuoka, K.; Matsubara, K.; Nakano, T.; Hieno, A.; Itakura, M.; Takahashi, K.; Kinugasa, S.; Kawaguchi, D.; Takahashi, Y.; Matsushita, Y. Radii of Gyration of Ring-Shaped Polystyrenes with High Purity in Dilute Solutions. Macromolecules 2012, 0– 4, DOI: 10.1021/ma202031w
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Gooßen, S.; Brás, A. R.; Pyckhout-Hintzen, W.; Wischnewski, A.; Richter, D.; Rubinstein, M.; Roovers, J.; Lutz, P. J.; Jeong, Y.; Chang, T.; Vlassopoulos, D. Influence of the Solvent Quality on Ring Polymer Dimensions. Macromolecules 2015, 48, 1598– 1605, DOI: 10.1021/ma502518p
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Influence of the Solvent Quality on Ring Polymer Dimensions
Goossen, Sebastian; Bras, Ana R.; Pyckhout-Hintzen, Wim; Wischnewski, Andreas; Richter, Dieter; Rubinstein, Michael; Roovers, Jacques; Lutz, Pierre J.; Jeong, Youncheol; Chang, Taihyun; Vlassopoulos, Dimitris
Macromolecules (Washington, DC, United States) (2015), 48 (5), 1598-1605CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
We present a systematic investigation of well-characterized, exptl. pure polystyrene (PS) rings with molar mass of 161 000 g/mol in dil. solns. We measure the ring form factor at θ- and good-solvent conditions as well as in a polymeric solvent (linear PS of roughly comparable molar mass) by means of small-angle neutron scattering (SANS). Addnl. dynamic light scattering (DLS) measurements support the SANS data and help elucidate the role of solvent quality and soln. prepn. The results indicate the increase of ring dimensions as the solvent quality improves. Furthermore, the exptl. form factors in both θ-solvent and linear matrix behave as ideal rings and are fully superimposable. The nearly Gaussian conformations of rings in a melt of linear chains provide evidence of threading of linear chains through rings. The latter result has implications for the dynamics of ring-linear polymer mixts.
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Higgins, J. S.; Dodgson, K.; Semlyen, J. A. Studies of Cyclic and Linear Poly(Dimethyl Siloxanes): 3. Neutron Scattering Measurements of the Dimensions of Ring and Chain Polymers. Polymer 1979, 20, 553– 558, DOI: 10.1016/0032-3861(79)90164-2
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Studies of cyclic and linear poly(dimethyl siloxanes). 3. Neutron scattering measurements of the dimensions of ring and chain polymers
Higgins, J. S.; Dodgson, K.; Semlyen, J. A.
Polymer (1979), 20 (5), 553-8CODEN: POLMAG; ISSN:0032-3861.
The chain dimensions of linear and cyclic poly(di-Me siloxanes) were detd. in C6D6 soln. by small-angle neutron scattering measurements. The av. dimensions of the cyclic polymers in fractions of z-av. d.p. 130-550 were considerably smaller than those of the corresponding linear polymers. The ratio of the z-av. radii of gyration of linear and cyclic polymers was ∼1.9 compared with a theor. value of 2.0 for flexible high polymers unperturbed by excluded vol. effects.
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Edwards, C. J. C.; Richards, R. W.; Stepto, R. F. T.; Dodgson, K.; Higgins, J. S.; Semlyen, J. A. Studies of Cyclic and Linear Poly(Dimethyl Siloxanes): 14. Particle Scattering Functions. Polymer 1984, 25, 365– 368, DOI: 10.1016/0032-3861(84)90289-1
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Studies of cyclic and linear poly(dimethylsiloxanes). 14. Particle scattering functions
Edwards, C. J. C.; Richards, R. W.; Stepto, R. F. T.; Dodgson, K.; Higgins, J. S.; Semlyen, J. A.
Polymer (1984), 25 (3), 365-8CODEN: POLMAG; ISSN:0032-3861.
Particle scattering functions, P(Q) (where Q represents the wave vector), were calcd. using a Monte Carlo method for cyclic and linear poly(dimethylsiloxanes) (PDMS) contg. ≤100 skeletal bonds. A max. was found in the Kratky plot at u (= Q〈s2〉0.5) ≈2.0 for cyclic PDMS [with root-mean-square radius of gyration 〈s2〉0.5)], and this was in satisfactory agreement with the anal. calcns. of E. F. Casassa (1965) and of W. Burchard and M. Schmidt (1980). In addn., other clearly-defined max. were found at u ≈5.0 for PDMS ring mols. with less than or ≈40 skeletal atoms. These max. were believed to be characteristic of small cyclic mols. as they were also predicted for small polymethylene rings. Comparisons were made with exptl. small-angle neutron scattering data for cyclic and linear PDMS. A single max. in the exptl. Kratky plot at u ≈2.0 was found for PDMS ring mols. with an av. of 550 skeletal atoms. The exptl. data for cyclic PDMS were in better agreement with the Monte Carlo calcns. of P(u) than with anal. predictions u ≈2.0.
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Coudane, J.; Ustariz, C.; Schwach, G.; Vert, M. More about the Stereodependence of DD and LL Pair Linkages during the Ring-Opening Polymerization of Racemic Lactide. J. Polym. Sci. Part A: Polym. Chem. 1996, 35, 1651– 1658
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Jem, K. J.; Tan, B. Advanced Industrial and Engineering Polymer Research The Development and Challenges of Poly ( Lactic Acid ) and Poly ( Glycolic Acid ). Adv. Ind. Eng. Polym. Res. 2020, 3, 60– 70, DOI: 10.1016/j.aiepr.2020.01.002
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Gross, R. A.; Kalra, B. Biodegradable Polymers for the Environment. Science 2002, 297, 803– 807, DOI: 10.1126/science.297.5582.803
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Biodegradable polymers for the environment
Gross, Richard A.; Kalra, Bhanu
Science (Washington, DC, United States) (2002), 297 (5582), 803-807CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
A review. Biodegradable polymers are designed to degrade upon disposal by the action of living organisms. Extraordinary progress has been made in the development of practical processes and products from polymers such as starch, cellulose, and lactic acid. The need to create alternative biodegradable water-sol. polymers for down-the-drain products such as detergents and cosmetics has taken on increasing importance. Consumers have, however, thus far attached little or no added value to the property of biodegradability, forcing industry to compete head-to-head on a cost-performance basis with existing familiar products. In addn., no suitable infrastructure for the disposal of biodegradable materials exists as yet.
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Mehta, R.; Kumar, V.; Bhunia, H.; Upadhyay, S. N. Synthesis of Poly(Lactic Acid): A Review. J. Macromol. Sci. - Polym. Rev. 2005, 45, 325– 349, DOI: 10.1080/15321790500304148
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Synthesis of poly(lactic acid): A review
Mehta, Rajeev; Kumar, Vineet; Bhunia, Haripada; Upadhyay, S. N.
Journal of Macromolecular Science, Polymer Reviews (2005), C45 (4), 325-349CODEN: JMSPCG; ISSN:1532-1797. (Taylor & Francis, Inc.)
This paper presents a review on poly(lactic acid) (PLA) with focus on its stereochem., synthesis via ring-opening polymn., reaction kinetics and thermodn., synthesis of low mol. wt. polymer, a continuous process for prodn. of PLA from lactic acid, and blends. The different polymn. mechanisms which have been proposed in the literature are also summarized. Various catalyst systems, solvents, and reaction temps. and times give products of an entire range of mol. wts., ranging from a few thousand to over a million. Modeling and simulation of the ring-opening polymn. of lactide is also discussed.
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Baran, J.; Duda, A.; Kowalski, A.; Szymanski, R.; Penczek, S. Intermolecular Chain Transfer to Polymer with Chain Scission: General Treatment and Determination of k,/Kt, in L,L-Lactide Polymerization. Macromol. Rapid Commun. 1997, 333, 325– 333, DOI: 10.1002/marc.1997.030180409
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Piromjitpong, P.; Ratanapanee, P.; Thumrongpatanaraks, W.; Kongsaeree, P.; Phomphrai, K. Synthesis of Cyclic Polylactide Catalysed by Bis(Salicylaldiminato)Tin(Ii) Complexes. Dalton Trans. 2012, 41, 12704– 12710, DOI: 10.1039/c2dt31678a
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Synthesis of cyclic polylactide catalysed by bis(salicylaldiminato)tin(II) complexes
Piromjitpong, Parichat; Ratanapanee, Passachon; Thumrongpatanaraks, Wipavee; Kongsaeree, Palangpon; Phomphrai, Khamphee
Dalton Transactions (2012), 41 (41), 12704-12710CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
Eight bis(salicylaldiminato)tin(II) complexes have been synthesized from the reaction of Sn[N(SiMe3)2]2 and 2 equiv of the corresponding ligands at room temp. The ligands, synthesized from salicylaldehyde and amines, were designed to have different electronic and steric properties using different amines to synthesize the tin(II) complexes as aniline (2a), 2,6-dimethylaniline (2b), 2,6-diisopropylaniline (2c), 4-methoxyaniline (2d), 4-trifluoromethylaniline (2e), methylamine (2g), and tert-butylamine (2h). Ligand variation at the salicyl group synthesized from 4-bromosalicylaldehyde and 2,6-diisopropylaniline was used to form complex 2f. Complex 2c was characterized crystallog. All catalysts were active for the neat polymn. of L-lactide at 115 °C. At a lactide : Sn molar ratio of 10:1, cyclic polylactide (PLA) was obtained as demonstrated by 1H NMR and mass spectrometry. Addn. of 1 equiv of benzyl alc. in the polymn. produced linear PLA. At a higher lactide : Sn molar ratio of 200:1, high mol. wt. PLAs with Mn up to 132 200 Da were obtained. Results from GPC coupled with light scattering detector and viscometer suggested that they are cyclic PLA. The order of reactivity based on conversion was detd. to be 2c < 2b < 2a in accordance with lower steric hindrance. For electronic contribution, the order of 2e < 2a < 2d was obsd. in agreement with the increasing electron donation of the ligands. Complex 2g having the smallest substituents was found to be the most active catalyst.
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Kricheldorf, H. R.; Lomadze, N.; Schwarz, G. Cyclic Polylactides by Imidazole-Catalyzed Polymerization of L-Lactide. Macromolecules 2008, 41, 7812– 7816, DOI: 10.1021/ma801519t
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Cyclic Polylactides by Imidazole-Catalyzed Polymerization of L-Lactide
Kricheldorf, Hans R.; Lomadze, Nino; Schwarz, Gert
Macromolecules (Washington, DC, United States) (2008), 41 (21), 7812-7816CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
Heating of L-lactide with imidazole to 98-100 °C resulted in complete polymn. within 48 h. Even-numbered cycles resulting from end-to-end cyclization were the only reaction products after 4 h, but the polymn. process was accompanied by intensive racemization. Longer reaction times favored equilibration reactions with formation of odd-numbered cycles. Variation of the monomer-initiator ratio at 120 °C had little influence on the mol. wt. After 8 h at 150 °C, equal quantities of odd- and even-numbered cycles were found, indicating complete equilibration. Other protic heterocycles such as 1,2,4-triazole, benzimidazolyl acetonitrile, uracil, or hypoxanthine were not active as initiators/catalysts at 120 °C. However, the tertiary amine N-methylimidazole also catalyzes the formation of cyclic polylactides together with several byproducts. The reaction mechanisms are discussed.
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Kricheldorf, H. R.; Weidner, S. M. High Molar Mass Cyclic Poly(L-Lactide) via Ring-Expansion Polymerization with Cyclic Dibutyltin Bisphenoxides. Eur. Polym. J. 2018, 105, 158– 166, DOI: 10.1016/j.eurpolymj.2018.05.036
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High molar mass cyclic poly(L-lactide) via ring-expansion polymerization with cyclic dibutyltin bisphenoxides
Kricheldorf, Hans R.; Weidner, Steffen M.
European Polymer Journal (2018), 105 (), 158-166CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Ltd.)
Two new catalysts (SnNa and SnBi) were prepd. from dibutyltin oxide and 2,2'-dihydroxybiphenyl or 2,2'dihydroxy(1,1'-binaphtyl). These catalysts enabled rapid polymns. of L-lactide at 160 or 180 °C in bulk, whereby almost exclusively cyclic polylactides were formed. These polymns. were free of racemization and yielded pol(L-lactide)s having wt. av. mol. wts. (Mw's) up to 140 000 g mol-1. The Mw's varied little with the Lac/Cat ratio as expected for a ring expansion polymn. (REP). Polymns. performed in bulk at 140, 120 and 102 °C yielded cyclic polylactides with lower mol. wts. At 102 °C a strong predominance of even-numbered cycles was found with SnNa as catalyst. SnNa can also catalyze alc.-initiated ROPs yielding linear poly(L-lactide) free of cyclics.
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Meyer, A.; Weidner, S. M.; Kricheldorf, H. R. Stereocomplexation of Cyclic Polylactides with Each Other and with Linear Poly(l-Lactide)S. Polym. Chem. 2019, 10, 6191– 6199, DOI: 10.1039/c9py01236b
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Stereocomplexation of cyclic polylactides with each other and with linear poly(L-lactide)s
Meyer, Andreas; Weidner, Steffen M.; Kricheldorf, Hans R.
Polymer Chemistry (2019), 10 (45), 6191-6199CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
Two kinds of cyclic poly(D- and L-lactide)s were synthesized, namely CI labeled samples mainly consisting of even-numbered cycles with low dispersity and CII, CIII or CIV-labeled ones consisting of equal amts. of even and odd-numbered cycles with high dispersity and higher mol. wts. (Mw up to 300 000). Furthermore, linear poly(L-lactide)s were prepd. by initiation with ethanol and in both series the mol. wt. was varied. The formation of stereocomplexes from cyclic poly(D-lactide)s and all kinds of poly(L-lactide)s was performed in dichloromethane/toluene mixts. The stereocomplexes crystd. from the reaction mixt. were characterized in the virgin state and after annealing at 205°C. Stereocomplexes free of stereohomopolymers with crystallinities up to 80% were obtained from all expts. in yields ranging from 60 to 80%. Despite the high annealing temp. (maintained for 1 h), little transesterification was obsd. and the crystallinity slightly increased.
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Ungpittagul, T.; Wongmahasirikun, P.; Phomphrai, K. Synthesis and Characterization of Guanidinate Tin(II) Complexes for Ring-Opening Polymerization of Cyclic Esters. Dalton Trans. 2020, 49, 8460– 8471, DOI: 10.1039/d0dt01115k
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Synthesis and characterization of guanidinate tin(II) complexes for ring-opening polymerization of cyclic esters
Ungpittagul, Thasanaporn; Wongmahasirikun, Phonpimon; Phomphrai, Khamphee
Dalton Transactions (2020), 49 (25), 8460-8471CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
Novel homoleptic and heteroleptic (guanidinate)tin(II) complexes were successfully synthesized and structurally characterized. The first heteroleptic (guanidinato)tin(II) alkoxide complex was synthesized but found to be unstable leading to the corresponding bis(guanidinate)tin(II) complex. The catalytic activities of bis(guanidinate)tin(II) complexes having different substituents at the nitrogen atoms (iso-Pr (1), cyclohexyl (2), and p-tolyl (3)) were investigated in the ring-opening polymn. (ROP) of ε-caprolactone (ε-CL) and lactide (LA). The lone pair electrons of the tin(II) atom were proposed to act as an initiator similar to N-heterocyclic carbenes. Among the synthesized catalysts, complex 1 having less steric hindrance efficiently catalyzed both homo- and copolymns. of ε-CL and LA giving high mol. wt. cyclic polyesters. Transesterification was found to be the major contributor to the cyclization to cyclic polyesters.
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Lindner, P.; Schweins, R. The D11 Small-Angle Scattering Instrument: A New Benchmark for SANS. Neutron News 2010, 21, 15– 18, DOI: 10.1080/10448631003697985
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Arnold, O.; Bilheux, J. C.; Borreguero, J. M.; Buts, A.; Campbell, S. I.; Chapon, L.; Doucet, M.; Draper, N.; Ferraz Leal, R.; Gigg, M. A.; Lynch, V. E.; Markvardsen, A.; Mikkelson, D. J.; Mikkelson, R. L.; Miller, R.; Palmen, K.; Parker, P.; Passos, G.; Perring, T. G.; Peterson, P. F.; Ren, S.; Reuter, M. A.; Savici, A. T.; Taylor, J. W.; Taylor, R. J.; Tolchenov, R.; Zhou, W.; Zikovsky, J. Mantid - Data Analysis and Visualization Package for Neutron Scattering and μ SR Experiments. Nucl. Instrum. Methods Phys. Res., Sect. A 2014, 764, 156– 166, DOI: 10.1016/j.nima.2014.07.029
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Mantid-Data analysis and visualization package for neutron scattering and μ SR experiments
Arnold, O.; Bilheux, J. C.; Borreguero, J. M.; Buts, A.; Campbell, S. I.; Chapon, L.; Doucet, M.; Draper, N.; Ferraz Leal, R.; Gigg, M. A.; Lynch, V. E.; Markvardsen, A.; Mikkelson, D. J.; Mikkelson, R. L.; Miller, R.; Palmen, K.; Parker, P.; Passos, G.; Perring, T. G.; Peterson, P. F.; Ren, S.; Reuter, M. A.; Savici, A. T.; Taylor, J. W.; Taylor, R. J.; Tolchenov, R.; Zhou, W.; Zikovsky, J.
Nuclear Instruments & Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment (2014), 764 (), 156-166CODEN: NIMAER; ISSN:0168-9002. (Elsevier B.V.)
The Mantid framework is a software soln. developed for the anal. and visualization of neutron scattering and muon spin measurements. The framework is jointly developed by software engineers and scientists at the ISIS Neutron and Muon Facility and the Oak Ridge National Lab. The objectives, functionality and novel design aspects of Mantid are described.
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Könnecke, M.; Akeroyd, F. A.; Bernstein, H. J.; Brewster, A. S.; Campbell, S. I.; Clausen, B.; Cottrell, S.; Hoffmann, J. U.; Jemian, P. R.; Männicke, D.; Osborn, R.; Peterson, P. F.; Richter, T.; Suzuki, J.; Watts, B.; Wintersberger, E.; Wuttke, J. The NeXus Data Format. J. Appl. Crystallogr. 2015, 48, 301– 305, DOI: 10.1107/S1600576714027575
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The NeXus data format
Konnecke Mark; Akeroyd Frederick A; Cottrell Stephen; Bernstein Herbert J; Brewster Aaron S; Campbell Stuart I; Peterson Peter F; Clausen Bjorn; Hoffmann Jens Uwe; Jemian Pete R; Mannicke David; Osborn Raymond; Richter Tobias; Suzuki Jiro; Watts Benjamin; Wintersberger Eugen; Wuttke Joachim
Journal of applied crystallography (2015), 48 (Pt 1), 301-305 ISSN:0021-8898.
NeXus is an effort by an international group of scientists to define a common data exchange and archival format for neutron, X-ray and muon experiments. NeXus is built on top of the scientific data format HDF5 and adds domain-specific rules for organizing data within HDF5 files, in addition to a dictionary of well defined domain-specific field names. The NeXus data format has two purposes. First, it defines a format that can serve as a container for all relevant data associated with a beamline. This is a very important use case. Second, it defines standards in the form of application definitions for the exchange of data between applications. NeXus provides structures for raw experimental data as well as for processed data.
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Hammouda, B. SANS from Homogenous Polymer Mixtures - a Unified Overview. Adv. Polym. Sci. 1993, 87– 133, DOI: 10.1007/BFb0025862
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SANS from homogeneous polymer mixtures: a unified overview
Hammouda, Boualem
Advances in Polymer Science (1993), 106 (Polymer Characteristics), 87-133CODEN: APSIDK; ISSN:0065-3195.
A review with 45 refs. on various modeling methods used to understand small-angle neutron scattering (SANS) data from homogeneous polymer systems.
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The phase behavior of binary blends of polyolefins is studied using small-angle neutron scattering. Component 1 is polyisobutylene (PIB), and component 2 is deuterated polybutadiene (dPB). Blends of these polymers are known to exhibit lower crit. soln. temps. The scattering intensity profiles from homogeneous PIB/dPB blends are fit to the RPA to det. χ, the Flory-Huggins interaction parameter. We demonstrate that χ depends on temp., blend compn., and component mol. wts.
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The crystal structure model of stereocomplex between poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA) with the L/D ratio of 50/50 was proposed by several groups [the space group P1 model by Okihara et al. (1991) and R3c or R‾3c model by Cartier et al. (1997)], among which the model of the space group R3c (or R‾3c) had been currently recognized as the most preferable one. However, the thus apparently established model cannot explain such an important exptl. fact that the stereocomplex is formed not only for the PLLA/PDLA blend of the L/D ratio 50/50 but also for the blends with the L/D ratio of 70/30-30/70. We have proposed here a new model with the space group P3, which can cover the SC structures of the L/D ratio in the range of 70/30-50/50-30/70. This model can show the more quant. reproducibility of the obsd. X-ray diffraction data for both the hkl and 000l reflection profiles. In particular the exptl. observation of the 0003 reflection is inconsistent with the previous model of the space group R3c, which requests the appearance of only the 000l with l = 6, 12, etc. In the newly proposed P3 model the mol. chains take the regular (3/1) helical conformation; however, the packing mode is not regular. The unit cell consists of the statistically disordered arrangement of the right-handed (R) and left-handed (L) chains of the upward (u) or downward (d) directionality. For example, in the case of the stereocomplex with L/D ratio 70/30, a pair of the left-handed downward (Ld) and right-handed upward (Ru) chains is located at one lattice site at the statistical occupancy of 70/30 ratio and another pair of the left-handed upward (Lu) and right-handed downward (Rd) chains is at the adjacent lattice site at the same 70/30 ratio. The unit cell contains the three sets of these two pairs, which are connected to each other by the sym. relation of the 3-fold rotation axis. The proposed statistical packing model of the upward and downward chains can explain such various observations as the spherulite formation or the existence of the lamellae with the chain folding structure in the spherulite, the solvent-induced change from the stereocomplex to the α form, and so on.
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Isothermal phase diagrams for the semicryst. poly-L-lactide (PLLA) and the amorphous poly-DL-lactide (PDLLA) in combination with several solvent-nonsolvent combinations (dioxane/water, dioxane/methanol, chloroform/methanol, and NMP/water) have been detd. The locations of the liq.-liq. miscibility gap, the solid-lipid miscibility gap and the vitrification boundary in the isothermal phase diagrams at 25°C were identified. The liq.-liq. miscibility gap for the systems with PLLA was located in the same compn. range as the corresponding systems with PDLLA. For the systems contg. PLLA solid-liq. demixing was thermodynamically preferred over liq.-liq. demixing. Attempts were made to correlate the exptl. findings with predictions on the basis of the Flory-Huggins theory for ternary solvents using interaction parameters derived from independent expts. Qual. agreement was found between the theor. predictions and the exptl. obtained liq.-liq. miscibility gap. No good agreement was found for the solid-liq. miscibility gap.
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Antoine, S.; Geng, Z.; Zofchak, E. S.; Chwatko, M.; Fredrickson, G. H.; Ganesan, V.; Hawker, C. J.; Lynd, N. A.; Segalman, R. A. Non-Intuitive Trends in Flory-Huggins Interaction Parameters in Polyether-Based Polymers. Macromolecules 2021, 54, 6670– 6677, DOI: 10.1021/acs.macromol.1c00134
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Non-intuitive Trends in Flory-Huggins Interaction Parameters in Polyether-Based Polymers
Antoine, Segolene; Geng, Zhishuai; Zofchak, Everett S.; Chwatko, Malgorzata; Fredrickson, Glenn H.; Ganesan, Venkat; Hawker, Craig J.; Lynd, Nathaniel A.; Segalman, Rachel A.
Macromolecules (Washington, DC, United States) (2021), 54 (14), 6670-6677CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
Recently, a variety of "click" or other additive chemistries have been introduced to functionalize polymers after polymn. to target specific applications, for example, membranes, catalysis, or drug delivery systems. It is generally assumed that the inclusion of these "click" linking groups has minimal impact on the thermodn. of the polymer as a whole. In this study, we demonstrate that the introduction of these click-derived units has a profound impact on the Flory-Huggins parameter of polyether derivs. Using RPA fits for small-angle X-ray scattering data from block copolymer pairs to est. the Flory-Huggins interaction parameter (χ), we detd. that poly(ethylene oxide) (PEO) and poly(allyl glycidyl ether) (PAGE), which differ only by the inclusion of an allyl sidechain, have a χ of 0.030 (at T = 34°C). While PEO is miscible with poly(lactide) (PLA) at nearly all temps., the PLA/PAGE χ detd. exptl. is 0.015 (at T = 30°C). Atomistic mol. dynamics simulations of PEO/PAGE oligomer blends show that upon blending, PEO chains contract and move closer together, while PAGE chains stretch and spread apart, indicating an enthalpic contribution to the χ parameter due to changes in polymer coordination resulting from the conformational asymmetry of PAGE and PEO. These studies demonstrate the large impact that functionalization and side-chain units have on the χ parameter of polymer pairs.
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Cite this: Macromolecules 2022, 55, 24, 11051–11058

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Published December 13, 2022

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Abstract
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Figure 1
Figure 1. Cyclic and linear topologies of PLA.
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Figure 2
Figure 2. Microstructures of PLA compared in this study with labeled stereocenters.
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Figure 3
Figure 3. Lactide monomer/s used to synthesize PLA analyzed in this study. The racemic lactide is a 50:50 mixture of l- and d-isomers. Isotactic PLLA was made using l-lactide only. (25)
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Figure 4
Figure 4. I(q) vs q plot of cyclic and linear poly(lactic acid) (PLA) samples over the full q range of 0.003 to 0.52 Å ^–1.
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Figure 5
Figure 5. I(q) vs q plots of cyclic (top, red) and linear (bottom, blue) PLA samples (C1 and L1 in Table 1) in acetone-d₆ and THF-d₈ at 15 and 40 °C.
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Figure 6
Figure 6. Graphs of χ_eff of PLA samples measured in this study at 15 and 40 °C in acetone-d₆ and THF-d₈. Textured bars denote different samples of the same topology as described in the legend. These data can also be seen as a graph of χ_eff vs 1/T in the Supporting Information (Figure S7).
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Figure 7
Figure 7. Graphs of ν against 1/T (Kelvin) for cyclic and linear PLA (left) samples. Textured bars denote different samples of the same topology as described in the legend. These data can also be seen as a graph of ν vs 1/T in the Supporting Information (Figure S8).
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Figure 8
Figure 8. Charts showing variation in average χ_eff of cyclic (red) and linear (blue) PLA samples of different microstructures illustrated previously in Figure 2.
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  A review. Cyclic polymers are the simplest topol. isomers of linear macromols., but exhibit properties that differ from linear chains in ways that remain imperfectly understood. The difficulty of synthesizing appropriately pure and high mol. wt. cyclic samples has hindered exptl. studies. Ring-closure methods, while versatile, are inherently limited in the range of mol. wts. that can be achieved. Ring-expansion methods are a much more promising strategy toward obtaining high mol. wt. cyclic polymers. The current review focuses on recent developments in ring-expansion polymn. strategies toward the synthesis of high mol. wt. cyclic polymers. Significant progress in the last decade has made the synthesis of cyclic polymers possible by a variety of methods, such as ruthenium- and tungsten-catalyzed ring-expansion metathesis polymn., organocatalytic and Lewis acid-catalyzed zwitterionic polymn., RAFT and nitroxide-mediated radical polymn., among many others. While the study of cyclic polymers has long been hampered by synthetic challenges, the recent resurgence of interest in this field presents an exciting opportunity for chemists. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.
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  2,2-Dibutyl-1,3-dioxa-2-stannanes prepd. from dibutyltin oxide and 1,3-propanediol or neopentanediol were used as cyclic initiators for polymns. of β-D,L-butyrolactone. Because these initiators were not reactive below 50 °C, all polymns. were conducted in bulk at temps. ≥50 °C. As evidenced by 13C NMR spectroscopy, the resulting poly(D,L-butyrolactone) is preferentially syndiotactic, but the percentage of syndiotactic diads decreases with increasing reaction temp. 1H NMR spectra proved that the insertion of lactones occurred at both Sn-O bonds of the cyclic initiators, and thus, the propagation yields automatically macrocyclic esters. The ring size increases with increasing monomer/initiator ratio and higher conversions. Selective ring opening with 1,2-dimercaptoethane produces linear polyesters with shorter elution times in GPC measurements than the corresponding macrocycles of the same mol. wt. Batchwise copolymns. with ε-caprolactone yielded macrocyclic block copolyesters which after ring-opening with dimercaptoethane turned into linear A-B-A triblock copolymers. However, when mixts. of both lactones were copolymd. at 100 °C, random copolyesters were obtained.
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  Polymns. of L-lactide in bulk at 160 or 180°C were performed with 1/1 mixts. of catechol (CA) or 4-tert-butylcatechol (BuCA) and tin(II)-2-ethylhexanoate (SnOct2) as catalysts and a variation of the Lac/Cat ratio. Wt. av. molar masses (Mw) up to 170,000 g mol-1 were obtained with CA and up to 120,000 g mol-1 with BuCA. The cyclic structure of the resulting poly(L-lactide)s was proven by MALDI-TOF mass spectrometry and by comparison of their hydrodynamic vols. with those of com. linear poly(L-lactide)s. The predominance of even-numbered cycles increased with lower temps. and shorter polymn. times. This finding indicates that the cyclic architecture is the results of a ring-expansion polymn. mechanism. Addn. of silylated BuCA as co-catalyst was less favorable than addn. of free BuCA.
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  Cyclic polyesters could improve the properties of degradable plastics, but routes to them that provide a product with faster rates, higher molar mass, and greater selectivity for cyclic vs. linear polymer are needed. Here, homogeneous Ce(III)-N-heterocyclic carbene (NHC) catalysts show outstanding activities (turn-over-frequency (TOF) > 864 000 h-1), excellent control, and selectivity for cyclic polylactide (PLA) topol. (>95%), yielding high molar mass PLA (60 < Mn < 250 kg mol-1). They efficiently produce cyclic PLA from rac-lactide or L-lactide and aliph. cyclic polyesters from ε-caprolactone or β-butyrolactone. The enhanced performances are only achievable from combining cooperative Lewis acidic cerium(III) and hemilabile N-heterocyclic carbene functionalities.
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  Ring-opening polymn. (ROP) is a powerful synthetic methodol. for the chem. synthesis of technol. important biodegradable aliph. polyesters from cyclic esters or lactones. However, the bioderived five-membered γ-butyrolactone (γ-BL) is commonly referred as 'non-polymerizable' because of its low strain energy. The chem. synthesis of poly(γ-butyrolactone) (PγBL) through the ROP process has been realized only under ultrahigh pressure (20,000 atm, 160 °C) and only produces oligomers. Here we report that the ROP of γ-BL can, with a suitable catalyst, proceed smoothly to high conversions (90%) under ambient pressure to produce PγBL materials with a no.-av. mol. wt. up to 30 kg mol-1 and with controlled linear and/or cyclic topologies. Remarkably, both linear and cyclic PγBLs can be recycled back into the monomer in quant. yield by simply heating the bulk materials at 220 °C (linear polymer) or 300 °C (cyclic polymer) for one hour, which thereby demonstrates the complete recyclability of PγBL.
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9. 9
  Hammami, N.; Majdoub, M.; Habas, J. P. Structure-Properties Relationships in Isosorbide-Based Polyacetals: Influence of Linear or Cyclic Architecture on Polymer Physicochemical Properties. Eur. Polym. J. 2017, 93, 795– 804, DOI: 10.1016/j.eurpolymj.2017.03.050
  9
  Structure-properties relationships in isosorbide-based polyacetals: Influence of linear or cyclic architecture on polymer physicochemical properties
  Hammami, Nadia; Majdoub, Mustapha; Habas, Jean-Pierre
  European Polymer Journal (2017), 93 (), 795-804CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Ltd.)
  A linear biobased polyacetal was prepd. from the reaction between isosorbide and methylene chloride according a one step procedure. Cyclic polyacetal was obtained using the previous linear polymer as precursor. The resp. architectures of both polymers and their chem. compns. were carefully established using 1H NMR and MALDI-TOF spectroscopies. Their mol. wt. characteristics were defined using a triple detection size exclusion chromatog. while their thermal characteristics were investigated by the conduction of calorimetric and thermogravimetric expts. The registering of the thermomech. properties of each kind of isosorbide-based polyacetal showed that the cyclic polymer was the only one able to show a rubbery plateau. This peculiarity was justified by calcn. of the threshold value above which entanglements were possible.
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10. 10
  Kricheldorf, H. R.; Weidner, S. M.; Scheliga, F. Synthesis of Cyclic Poly(l-Lactide) Catalyzed by Bismuth Salicylates─A Combination of Two Drugs. J. Polym. Sci. Part A: Polym. Chem. 2019, 57, 2056– 2063, DOI: 10.1002/pola.29473
  10
  Synthesis of cyclic poly(L-lactide) catalyzed by Bismuth Salicylates-A combination of two drugs
  Kricheldorf, Hans R.; Weidner, Steffen M.; Scheliga, Felix
  Journal of Polymer Science, Part A: Polymer Chemistry (2019), 57 (19), 2056-2063CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)
  L-lactide was polymd. in bulk at 160 or 180°C with mixts. of bismuth subsalicylate (BiSub) and salicylic (SA) as catalysts. The SA/Bi ratio and the monomer/Bi ratio were varied. The highest mol. wts. (wt. av., Mw) were achieved at a SA/Bi ratio of 1/1 (Mw up to 92 000 g mol-1). L-Lactide was also polymd. with combinations of BiSub and silylated SA, and Mw values up to 120 000 g mol-1 were achieved at 180°C. MALDI-TOF mass spectrometry and Mark-Houwink-Sakurada measurements proved that under optimized reaction conditions the resulting polylactides consist of cycles.
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11. 11
  Tu, X. Y.; Liu, M. Z.; Wei, H. Recent Progress on Cyclic Polymers: Synthesis, Bioproperties, and Biomedical Applications. J. Polym. Sci. Part A: Polym. Chem. 2016, 54, 1447– 1458, DOI: 10.1002/pola.28051
  11
  Recent progress on cyclic polymers: Synthesis, bioproperties, and biomedical applications
  Tu, Xiao-Yan; Liu, Ming-Zhu; Wei, Hua
  Journal of Polymer Science, Part A: Polymer Chemistry (2016), 54 (11), 1447-1458CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)
  A review. Polymer topologies exert a significant effect on its properties, and polymer nanostructures with advanced architectures, such as cyclic polymers, star-shaped polymers, and hyperbranched polymers, are a promising class of materials with advantages over conventional linear counterparts. Cyclic polymers, due to the lack of polymer chain ends, have displayed intriguing phys. and chem. properties. Such uniqueness has drawn considerable attention over the past decade. The current review focuses on the recent progress in the design and development of cyclic polymer with an emphasis on its synthesis and bio-related properties and applications. Two primary synthetic strategies towards cyclic polymers, i.e., ring-expansion polymn. and ring-closure reaction are summarized. The bioproperties and biomedical applications of cyclic polymers are then highlighted. In the end, the future directions of this rapidly developing research field are discussed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016.
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12. 12
  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, DOI: 10.1038/nmat2292
  12
  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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13. 13
  Halverson, J. D.; Lee, W. B.; Grest, G. S.; Grosberg, A. Y.; Kremer, K. Molecular Dynamics Simulation Study of Nonconcatenated Ring Polymers in a Melt. I. Statics. J. Chem. Phys. 2011, 134, 15, DOI: 10.1063/1.3587137
  There is no corresponding record for this reference.
14. 14
  Doi, Y.; Matsubara, K.; Ohta, Y.; Nakano, T.; Kawaguchi, D.; Takahashi, Y.; Takano, A.; Matsushita, Y. Melt Rheology of Ring Polystyrenes with Ultrahigh Purity. Macromolecules 2015, 48, 3140– 3147, DOI: 10.1021/acs.macromol.5b00076
  14
  Melt Rheology of Ring Polystyrenes with Ultrahigh Purity
  Doi, Yuya; Matsubara, Kazuki; Ohta, Yutaka; Nakano, Tomohiro; Kawaguchi, Daisuke; Takahashi, Yoshiaki; Takano, Atsushi; Matsushita, Yushu
  Macromolecules (Washington, DC, United States) (2015), 48 (9), 3140-3147CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
  The melt rheol. of highly-purified ring polystyrenes in a wide range of mol. wts. (10K ≤ Mw ≤ 240K g/mol) was investigated. All the rings revealed no obvious rubbery plateau and faster terminal relaxation compared to the linear counterparts. The rheol. data obtained were compared with some theor. models such as the Rouse ring model and the lattice-animal model. Moreover, two rheol. parameters, zero-shear viscosities η0 and the steady-state recoverable compliances Je, were estd., and their Mw dependence was discussed. From these data anal., it was found that relaxation mechanisms of ring chains can be divided into three categories depending on their Mw as follows: (1) Smaller rings (Mw ≤ 20K) exhibit faster terminal relaxation than the predicted Rouse rings. This behavior is related to the difference of the local chain conformation from linear chains. (2) Rings with the moderate mol. wt. (40K ≤ Mw ≤ 90K) exhibit dynamic moduli similar to the Rouse ring prediction. (3) A larger ring (Mw > 90K) also shows deviant behavior from the Rouse chain because its relaxation time is much longer than the Rouse ring prediction and also the lattice-animal model, where some intermol. interactions are considered to occur.
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15. 15
  Pasquino, R.; Vasilakopoulos, T. C.; Jeong, Y. C.; Lee, H.; Rogers, S.; Sakellariou, G.; Allgaier, J.; Takano, A.; Brás, A. R.; Chang, T.; Gooßen, S.; Pyckhout-Hintzen, W.; Wischnewski, A.; Hadjichristidis, N.; Richter, D.; Rubinstein, M.; Vlassopoulos, D. Viscosity of Ring Polymer Melts. ACS Macro Lett. 2013, 2, 874– 878, DOI: 10.1021/mz400344e
  15
  Viscosity of Ring Polymer Melts
  Pasquino, Rossana; Vasilakopoulos, Thodoris C.; Jeong, Youn Cheol; Lee, Hyojoon; Rogers, Simon; Sakellariou, George; Allgaier, Jurgen; Takano, Atsushi; Bras, Ana R.; Chang, Taihyun; Goossen, Sebastian; Pyckhout-Hintzen, Wim; Wischnewski, Andreas; Hadjichristidis, Nikos; Richter, Dieter; Rubinstein, Michael; Vlassopoulos, Dimitris
  ACS Macro Letters (2013), 2 (10), 874-878CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
  We have measured the linear rheol. of critically purified ring polyisoprenes, polystyrenes, and polyethylene oxides of different molar masses. The ratio of the zero-shear viscosities of linear polymer melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed as a function of the no. of entanglements Z. In the unentangled regime η0,linear/η0,ring is virtually const., consistent with the earlier data, atomistic simulations, and the theor. expectation η0,linear/η0,ring = 2. In the entanglement regime, the Z-dependence of ring viscosity is much weaker than that of linear polymers, in qual. agreement with predictions from scaling theory and simulations. The power-law extd. from the available exptl. data in the rather limited range 1 < Z < 20, η0,linear/η0,ring ∼ Z1.2±0.3, is weaker than the scaling prediction (η0,linear/η0,ring ∼ Z1.6±0.3) and the simulations (η0,linear/η0,ring ∼ Z2.0±0.3). Nevertheless, the present collection of state-of-the-art exptl. data unambiguously demonstrates that rings exhibit a universal trend clearly departing from that of their linear counterparts, and hence it represents a major step toward resolving a 30-yr-old problem.
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16. 16
  Gooßen, S.; Brás, A. R.; Krutyeva, M.; Sharp, M.; Falus, P.; Feoktystov, A.; Gasser, U.; Pyckhout-Hintzen, W.; Wischnewski, A.; Richter, D. Molecular Scale Dynamics of Large Ring Polymers. Phys. Rev. Lett. 2014, 113, 1– 5, DOI: 10.1103/PhysRevLett.113.168302
  There is no corresponding record for this reference.
17. 17
  Yan, Z. C.; Costanzo, S.; Jeong, Y.; Chang, T.; Vlassopoulos, D. Linear and Nonlinear Shear Rheology of a Marginally Entangled Ring Polymer. Macromolecules 2016, 49, 1444– 1453, DOI: 10.1021/acs.macromol.5b02651
  17
  Linear and Nonlinear Shear Rheology of a Marginally Entangled Ring Polymer
  Yan, Zhi-Chao; Costanzo, Salvatore; Jeong, Youncheol; Chang, Taihyun; Vlassopoulos, Dimitris
  Macromolecules (Washington, DC, United States) (2016), 49 (4), 1444-1453CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
  We present systematic, unique linear and nonlinear shear rheol. data of an exptl. pure ring polystyrene and its linear precursor. This polymer was synthesized anionically and characterized by interaction chromatog. and fractionation at the crit. condition. Its wt.-av. molar mass is 84 kg/mol; i.e., it is marginally entangled (entanglement no. Z ≈ 5). Its linear viscoelastic response appears to be better described by the Rouse model (accounting for ring closure) rather than the lattice-animal-based model, suggesting a transition from unentangled to entangled ring dynamics. The failure of both models in the terminal region may reflect the remaining unlinked linear contaminants and/or ring-ring interpenetration. The viscosity evolution at different shear rates was measured using a homemade cone-partitioned plate fixture in order to avoid edge fracture instabilities. Our findings suggest that rings are much less shear thinning compared to their linear counterparts, whereas both obey the Cox-Merz rule. The shear stress (or viscosity) overshoot is much weaker for rings compared to linear chains, pointing to the fact that their effective deformation is smaller. Finally, step strain expts. indicate that the damping function data of ring polymers clearly depart from the Doi-Edwards prediction for entangled linear chains, exhibiting a weak thinning response. These findings indicate that these marginally entangled rings behave like effectively unentangled chains with finite extensibility and deform much less in shear flow compared to linear polymers. They can serve as guideline for further investigation of the nonlinear dynamics of ring polymers and the development of constitutive equations.
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18. 18
  Gartner, T. E.; Haque, F. M.; Gomi, A. M.; Grayson, S. M.; Hore, M. J. A.; Jayaraman, A. Scaling Exponent and Effective Interactions in Linear and Cyclic Polymer Solutions: Theory, Simulations, and Experiments. Macromolecules 2019, 52, 4579– 4589, DOI: 10.1021/acs.macromol.9b00600
  18
  Scaling Exponent and Effective Interactions in Linear and Cyclic Polymer Solutions: Theory, Simulations, and Experiments
  Gartner, Thomas E., III; Haque, Farihah M.; Gomi, Aila M.; Grayson, Scott M.; Hore, Michael J. A.; Jayaraman, Arthi
  Macromolecules (Washington, DC, United States) (2019), 52 (12), 4579-4589CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
  Cyclic polymers have garnered increasing attention in the materials community as lack of free-chain ends in cyclic polymers results in significant differences in structure, thermodn., and dynamics compared to their linear counterparts. Yet, key open questions remain about how cyclic polymer chain conformations and effective interactions in soln. change as a function of solvent quality, ring closure chem., and the presence/absence of common synthetic impurities. We use coarse-grained mol. dynamics simulations, polymer ref. interaction site model theory, and small-angle neutron-scattering expts. on polystyrene in d-cyclohexane to demonstrate how linear and cyclic polymer chain configurations, scaling, and effective interactions are influenced by solvent quality and polymer concn. We find that the balance between the available intra- vs. interchain contacts in soln. dictate the trends in cyclic polymer size scaling and effective polymer-solvent and polymer-polymer interactions; these results are largely insensitive to the ring closure chem. and the presence of linear or cyclic dimer impurities. This study provides the broader polymer science and engineering community fundamental insights into how synthesis, purifn., and assembly of cyclic polymers in solvent(s) impact the resulting chain structure and polymer soln. thermodn.
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19. 19
  Suzuki, J.; Takano, A.; Matsushita, Y. The Theta-Temperature Depression Caused by Topological Effect in Ring Polymers Studied by Monte Carlo Simulation. J. Chem. Phys. 2011, 135, 204903, DOI: 10.1063/1.3663383
  19
  The theta-temperature depression caused by topological effect in ring polymers studied by Monte Carlo simulation
  Suzuki, Jiro; Takano, Atsushi; Matsushita, Yushu
  Journal of Chemical Physics (2011), 135 (20), 204903/1-204903/6CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
  We studied equil. conformations of linear and ring polymers in dil. solns. over the wide range of segment no. N of up to 2048 with Monte Carlo simulation, and evaluated N dependence of the radii of gyration, Rg, of chains. The polymer mols. treated in this study are assumed to be composed of beads and bonds, and they are put in a three-dimensional face-centered cubic (FCC) lattice. The values of Flory's crit. exponent, ν, for linear and ring polymers were estd. from the N dependence of Rg, and the temps. at which ν reach 1/2 were obtained. Here we define those as Θ-temps. in this report. The simulation result shows that the Θ-temp. for ring polymers is evidently lower than that of the linear polymers, and the origin of the Θ-temp. depression is discussed. Since Rg of a ring polymer is smaller than that for a linear polymer at the same N and temp., the segment d. for a ring polymer is increased by the topol. effect and the repulsive force between segments of a ring polymer at the Θ-temp. for a linear polymer is stronger. Thus, the origin of the Θ-temp. depression for ring polymers is the repulsive force emphasized by the topol. effect of rings. (c) 2011 American Institute of Physics.
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20. 20
  Takano, A.; Kushida, Y.; Ohta, Y.; Masuoka, K.; Matsushita, Y. The Second Virial Coefficients of Highly-Purified Ring Polystyrenes in Cyclohexane. Polymer 2009, 50, 1300– 1303, DOI: 10.1016/j.polymer.2009.01.019
  20
  The second virial coefficients of highly-purified ring polystyrenes in cyclohexane
  Takano, Atsushi; Kushida, Yuuki; Ohta, Yutaka; Masuoka, Keisuke; Matsushita, Yushu
  Polymer (2009), 50 (5), 1300-1303CODEN: POLMAG; ISSN:0032-3861. (Elsevier Ltd.)
  The second virial coeffs. A 2 of ring polystyrenes with high purity in cyclohexane were measured by light scattering in the temp. range 27.0-34.5 °C. The purity of four samples with M w of 16k, 42k, 110k and 570k was detd. to be all over 96% by HPLC. It has been found that A 2s of all the samples are definitely pos. at the theta temp. of linear polystyrene, 34.5 °C, and the measured values for four samples converged to zero at 27.7 °C with decreasing temp. This value is below the previously reported one, but it is quite consistent with the predicted value based on the topol. repulsive interaction among the ring polymer mols.
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21. 21
  Takano, A.; Ohta, Y.; Masuoka, K.; Matsubara, K.; Nakano, T.; Hieno, A.; Itakura, M.; Takahashi, K.; Kinugasa, S.; Kawaguchi, D.; Takahashi, Y.; Matsushita, Y. Radii of Gyration of Ring-Shaped Polystyrenes with High Purity in Dilute Solutions. Macromolecules 2012, 0– 4, DOI: 10.1021/ma202031w
  There is no corresponding record for this reference.
22. 22
  Gooßen, S.; Brás, A. R.; Pyckhout-Hintzen, W.; Wischnewski, A.; Richter, D.; Rubinstein, M.; Roovers, J.; Lutz, P. J.; Jeong, Y.; Chang, T.; Vlassopoulos, D. Influence of the Solvent Quality on Ring Polymer Dimensions. Macromolecules 2015, 48, 1598– 1605, DOI: 10.1021/ma502518p
  22
  Influence of the Solvent Quality on Ring Polymer Dimensions
  Goossen, Sebastian; Bras, Ana R.; Pyckhout-Hintzen, Wim; Wischnewski, Andreas; Richter, Dieter; Rubinstein, Michael; Roovers, Jacques; Lutz, Pierre J.; Jeong, Youncheol; Chang, Taihyun; Vlassopoulos, Dimitris
  Macromolecules (Washington, DC, United States) (2015), 48 (5), 1598-1605CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
  We present a systematic investigation of well-characterized, exptl. pure polystyrene (PS) rings with molar mass of 161 000 g/mol in dil. solns. We measure the ring form factor at θ- and good-solvent conditions as well as in a polymeric solvent (linear PS of roughly comparable molar mass) by means of small-angle neutron scattering (SANS). Addnl. dynamic light scattering (DLS) measurements support the SANS data and help elucidate the role of solvent quality and soln. prepn. The results indicate the increase of ring dimensions as the solvent quality improves. Furthermore, the exptl. form factors in both θ-solvent and linear matrix behave as ideal rings and are fully superimposable. The nearly Gaussian conformations of rings in a melt of linear chains provide evidence of threading of linear chains through rings. The latter result has implications for the dynamics of ring-linear polymer mixts.
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23. 23
  Higgins, J. S.; Dodgson, K.; Semlyen, J. A. Studies of Cyclic and Linear Poly(Dimethyl Siloxanes): 3. Neutron Scattering Measurements of the Dimensions of Ring and Chain Polymers. Polymer 1979, 20, 553– 558, DOI: 10.1016/0032-3861(79)90164-2
  23
  Studies of cyclic and linear poly(dimethyl siloxanes). 3. Neutron scattering measurements of the dimensions of ring and chain polymers
  Higgins, J. S.; Dodgson, K.; Semlyen, J. A.
  Polymer (1979), 20 (5), 553-8CODEN: POLMAG; ISSN:0032-3861.
  The chain dimensions of linear and cyclic poly(di-Me siloxanes) were detd. in C6D6 soln. by small-angle neutron scattering measurements. The av. dimensions of the cyclic polymers in fractions of z-av. d.p. 130-550 were considerably smaller than those of the corresponding linear polymers. The ratio of the z-av. radii of gyration of linear and cyclic polymers was ∼1.9 compared with a theor. value of 2.0 for flexible high polymers unperturbed by excluded vol. effects.
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24. 24
  Edwards, C. J. C.; Richards, R. W.; Stepto, R. F. T.; Dodgson, K.; Higgins, J. S.; Semlyen, J. A. Studies of Cyclic and Linear Poly(Dimethyl Siloxanes): 14. Particle Scattering Functions. Polymer 1984, 25, 365– 368, DOI: 10.1016/0032-3861(84)90289-1
  24
  Studies of cyclic and linear poly(dimethylsiloxanes). 14. Particle scattering functions
  Edwards, C. J. C.; Richards, R. W.; Stepto, R. F. T.; Dodgson, K.; Higgins, J. S.; Semlyen, J. A.
  Polymer (1984), 25 (3), 365-8CODEN: POLMAG; ISSN:0032-3861.
  Particle scattering functions, P(Q) (where Q represents the wave vector), were calcd. using a Monte Carlo method for cyclic and linear poly(dimethylsiloxanes) (PDMS) contg. ≤100 skeletal bonds. A max. was found in the Kratky plot at u (= Q〈s2〉0.5) ≈2.0 for cyclic PDMS [with root-mean-square radius of gyration 〈s2〉0.5)], and this was in satisfactory agreement with the anal. calcns. of E. F. Casassa (1965) and of W. Burchard and M. Schmidt (1980). In addn., other clearly-defined max. were found at u ≈5.0 for PDMS ring mols. with less than or ≈40 skeletal atoms. These max. were believed to be characteristic of small cyclic mols. as they were also predicted for small polymethylene rings. Comparisons were made with exptl. small-angle neutron scattering data for cyclic and linear PDMS. A single max. in the exptl. Kratky plot at u ≈2.0 was found for PDMS ring mols. with an av. of 550 skeletal atoms. The exptl. data for cyclic PDMS were in better agreement with the Monte Carlo calcns. of P(u) than with anal. predictions u ≈2.0.
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25. 25
  Coudane, J.; Ustariz, C.; Schwach, G.; Vert, M. More about the Stereodependence of DD and LL Pair Linkages during the Ring-Opening Polymerization of Racemic Lactide. J. Polym. Sci. Part A: Polym. Chem. 1996, 35, 1651– 1658
  There is no corresponding record for this reference.
26. 26
  Jem, K. J.; Tan, B. Advanced Industrial and Engineering Polymer Research The Development and Challenges of Poly ( Lactic Acid ) and Poly ( Glycolic Acid ). Adv. Ind. Eng. Polym. Res. 2020, 3, 60– 70, DOI: 10.1016/j.aiepr.2020.01.002
  There is no corresponding record for this reference.
27. 27
  Gross, R. A.; Kalra, B. Biodegradable Polymers for the Environment. Science 2002, 297, 803– 807, DOI: 10.1126/science.297.5582.803
  27
  Biodegradable polymers for the environment
  Gross, Richard A.; Kalra, Bhanu
  Science (Washington, DC, United States) (2002), 297 (5582), 803-807CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
  A review. Biodegradable polymers are designed to degrade upon disposal by the action of living organisms. Extraordinary progress has been made in the development of practical processes and products from polymers such as starch, cellulose, and lactic acid. The need to create alternative biodegradable water-sol. polymers for down-the-drain products such as detergents and cosmetics has taken on increasing importance. Consumers have, however, thus far attached little or no added value to the property of biodegradability, forcing industry to compete head-to-head on a cost-performance basis with existing familiar products. In addn., no suitable infrastructure for the disposal of biodegradable materials exists as yet.
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28. 28
  Mehta, R.; Kumar, V.; Bhunia, H.; Upadhyay, S. N. Synthesis of Poly(Lactic Acid): A Review. J. Macromol. Sci. - Polym. Rev. 2005, 45, 325– 349, DOI: 10.1080/15321790500304148
  28
  Synthesis of poly(lactic acid): A review
  Mehta, Rajeev; Kumar, Vineet; Bhunia, Haripada; Upadhyay, S. N.
  Journal of Macromolecular Science, Polymer Reviews (2005), C45 (4), 325-349CODEN: JMSPCG; ISSN:1532-1797. (Taylor & Francis, Inc.)
  This paper presents a review on poly(lactic acid) (PLA) with focus on its stereochem., synthesis via ring-opening polymn., reaction kinetics and thermodn., synthesis of low mol. wt. polymer, a continuous process for prodn. of PLA from lactic acid, and blends. The different polymn. mechanisms which have been proposed in the literature are also summarized. Various catalyst systems, solvents, and reaction temps. and times give products of an entire range of mol. wts., ranging from a few thousand to over a million. Modeling and simulation of the ring-opening polymn. of lactide is also discussed.
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29. 29
  Baran, J.; Duda, A.; Kowalski, A.; Szymanski, R.; Penczek, S. Intermolecular Chain Transfer to Polymer with Chain Scission: General Treatment and Determination of k,/Kt, in L,L-Lactide Polymerization. Macromol. Rapid Commun. 1997, 333, 325– 333, DOI: 10.1002/marc.1997.030180409
  There is no corresponding record for this reference.
30. 30
  Piromjitpong, P.; Ratanapanee, P.; Thumrongpatanaraks, W.; Kongsaeree, P.; Phomphrai, K. Synthesis of Cyclic Polylactide Catalysed by Bis(Salicylaldiminato)Tin(Ii) Complexes. Dalton Trans. 2012, 41, 12704– 12710, DOI: 10.1039/c2dt31678a
  30
  Synthesis of cyclic polylactide catalysed by bis(salicylaldiminato)tin(II) complexes
  Piromjitpong, Parichat; Ratanapanee, Passachon; Thumrongpatanaraks, Wipavee; Kongsaeree, Palangpon; Phomphrai, Khamphee
  Dalton Transactions (2012), 41 (41), 12704-12710CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
  Eight bis(salicylaldiminato)tin(II) complexes have been synthesized from the reaction of Sn[N(SiMe3)2]2 and 2 equiv of the corresponding ligands at room temp. The ligands, synthesized from salicylaldehyde and amines, were designed to have different electronic and steric properties using different amines to synthesize the tin(II) complexes as aniline (2a), 2,6-dimethylaniline (2b), 2,6-diisopropylaniline (2c), 4-methoxyaniline (2d), 4-trifluoromethylaniline (2e), methylamine (2g), and tert-butylamine (2h). Ligand variation at the salicyl group synthesized from 4-bromosalicylaldehyde and 2,6-diisopropylaniline was used to form complex 2f. Complex 2c was characterized crystallog. All catalysts were active for the neat polymn. of L-lactide at 115 °C. At a lactide : Sn molar ratio of 10:1, cyclic polylactide (PLA) was obtained as demonstrated by 1H NMR and mass spectrometry. Addn. of 1 equiv of benzyl alc. in the polymn. produced linear PLA. At a higher lactide : Sn molar ratio of 200:1, high mol. wt. PLAs with Mn up to 132 200 Da were obtained. Results from GPC coupled with light scattering detector and viscometer suggested that they are cyclic PLA. The order of reactivity based on conversion was detd. to be 2c < 2b < 2a in accordance with lower steric hindrance. For electronic contribution, the order of 2e < 2a < 2d was obsd. in agreement with the increasing electron donation of the ligands. Complex 2g having the smallest substituents was found to be the most active catalyst.
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31. 31
  Kricheldorf, H. R.; Lomadze, N.; Schwarz, G. Cyclic Polylactides by Imidazole-Catalyzed Polymerization of L-Lactide. Macromolecules 2008, 41, 7812– 7816, DOI: 10.1021/ma801519t
  31
  Cyclic Polylactides by Imidazole-Catalyzed Polymerization of L-Lactide
  Kricheldorf, Hans R.; Lomadze, Nino; Schwarz, Gert
  Macromolecules (Washington, DC, United States) (2008), 41 (21), 7812-7816CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
  Heating of L-lactide with imidazole to 98-100 °C resulted in complete polymn. within 48 h. Even-numbered cycles resulting from end-to-end cyclization were the only reaction products after 4 h, but the polymn. process was accompanied by intensive racemization. Longer reaction times favored equilibration reactions with formation of odd-numbered cycles. Variation of the monomer-initiator ratio at 120 °C had little influence on the mol. wt. After 8 h at 150 °C, equal quantities of odd- and even-numbered cycles were found, indicating complete equilibration. Other protic heterocycles such as 1,2,4-triazole, benzimidazolyl acetonitrile, uracil, or hypoxanthine were not active as initiators/catalysts at 120 °C. However, the tertiary amine N-methylimidazole also catalyzes the formation of cyclic polylactides together with several byproducts. The reaction mechanisms are discussed.
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32. 32
  Kricheldorf, H. R.; Weidner, S. M. High Molar Mass Cyclic Poly(L-Lactide) via Ring-Expansion Polymerization with Cyclic Dibutyltin Bisphenoxides. Eur. Polym. J. 2018, 105, 158– 166, DOI: 10.1016/j.eurpolymj.2018.05.036
  32
  High molar mass cyclic poly(L-lactide) via ring-expansion polymerization with cyclic dibutyltin bisphenoxides
  Kricheldorf, Hans R.; Weidner, Steffen M.
  European Polymer Journal (2018), 105 (), 158-166CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Ltd.)
  Two new catalysts (SnNa and SnBi) were prepd. from dibutyltin oxide and 2,2'-dihydroxybiphenyl or 2,2'dihydroxy(1,1'-binaphtyl). These catalysts enabled rapid polymns. of L-lactide at 160 or 180 °C in bulk, whereby almost exclusively cyclic polylactides were formed. These polymns. were free of racemization and yielded pol(L-lactide)s having wt. av. mol. wts. (Mw's) up to 140 000 g mol-1. The Mw's varied little with the Lac/Cat ratio as expected for a ring expansion polymn. (REP). Polymns. performed in bulk at 140, 120 and 102 °C yielded cyclic polylactides with lower mol. wts. At 102 °C a strong predominance of even-numbered cycles was found with SnNa as catalyst. SnNa can also catalyze alc.-initiated ROPs yielding linear poly(L-lactide) free of cyclics.
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33. 33
  Meyer, A.; Weidner, S. M.; Kricheldorf, H. R. Stereocomplexation of Cyclic Polylactides with Each Other and with Linear Poly(l-Lactide)S. Polym. Chem. 2019, 10, 6191– 6199, DOI: 10.1039/c9py01236b
  33
  Stereocomplexation of cyclic polylactides with each other and with linear poly(L-lactide)s
  Meyer, Andreas; Weidner, Steffen M.; Kricheldorf, Hans R.
  Polymer Chemistry (2019), 10 (45), 6191-6199CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
  Two kinds of cyclic poly(D- and L-lactide)s were synthesized, namely CI labeled samples mainly consisting of even-numbered cycles with low dispersity and CII, CIII or CIV-labeled ones consisting of equal amts. of even and odd-numbered cycles with high dispersity and higher mol. wts. (Mw up to 300 000). Furthermore, linear poly(L-lactide)s were prepd. by initiation with ethanol and in both series the mol. wt. was varied. The formation of stereocomplexes from cyclic poly(D-lactide)s and all kinds of poly(L-lactide)s was performed in dichloromethane/toluene mixts. The stereocomplexes crystd. from the reaction mixt. were characterized in the virgin state and after annealing at 205°C. Stereocomplexes free of stereohomopolymers with crystallinities up to 80% were obtained from all expts. in yields ranging from 60 to 80%. Despite the high annealing temp. (maintained for 1 h), little transesterification was obsd. and the crystallinity slightly increased.
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34. 34
  Ungpittagul, T.; Wongmahasirikun, P.; Phomphrai, K. Synthesis and Characterization of Guanidinate Tin(II) Complexes for Ring-Opening Polymerization of Cyclic Esters. Dalton Trans. 2020, 49, 8460– 8471, DOI: 10.1039/d0dt01115k
  34
  Synthesis and characterization of guanidinate tin(II) complexes for ring-opening polymerization of cyclic esters
  Ungpittagul, Thasanaporn; Wongmahasirikun, Phonpimon; Phomphrai, Khamphee
  Dalton Transactions (2020), 49 (25), 8460-8471CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
  Novel homoleptic and heteroleptic (guanidinate)tin(II) complexes were successfully synthesized and structurally characterized. The first heteroleptic (guanidinato)tin(II) alkoxide complex was synthesized but found to be unstable leading to the corresponding bis(guanidinate)tin(II) complex. The catalytic activities of bis(guanidinate)tin(II) complexes having different substituents at the nitrogen atoms (iso-Pr (1), cyclohexyl (2), and p-tolyl (3)) were investigated in the ring-opening polymn. (ROP) of ε-caprolactone (ε-CL) and lactide (LA). The lone pair electrons of the tin(II) atom were proposed to act as an initiator similar to N-heterocyclic carbenes. Among the synthesized catalysts, complex 1 having less steric hindrance efficiently catalyzed both homo- and copolymns. of ε-CL and LA giving high mol. wt. cyclic polyesters. Transesterification was found to be the major contributor to the cyclization to cyclic polyesters.
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35. 35
  Lindner, P.; Schweins, R. The D11 Small-Angle Scattering Instrument: A New Benchmark for SANS. Neutron News 2010, 21, 15– 18, DOI: 10.1080/10448631003697985
  There is no corresponding record for this reference.
36. 36
  Arnold, O.; Bilheux, J. C.; Borreguero, J. M.; Buts, A.; Campbell, S. I.; Chapon, L.; Doucet, M.; Draper, N.; Ferraz Leal, R.; Gigg, M. A.; Lynch, V. E.; Markvardsen, A.; Mikkelson, D. J.; Mikkelson, R. L.; Miller, R.; Palmen, K.; Parker, P.; Passos, G.; Perring, T. G.; Peterson, P. F.; Ren, S.; Reuter, M. A.; Savici, A. T.; Taylor, J. W.; Taylor, R. J.; Tolchenov, R.; Zhou, W.; Zikovsky, J. Mantid - Data Analysis and Visualization Package for Neutron Scattering and μ SR Experiments. Nucl. Instrum. Methods Phys. Res., Sect. A 2014, 764, 156– 166, DOI: 10.1016/j.nima.2014.07.029
  36
  Mantid-Data analysis and visualization package for neutron scattering and μ SR experiments
  Arnold, O.; Bilheux, J. C.; Borreguero, J. M.; Buts, A.; Campbell, S. I.; Chapon, L.; Doucet, M.; Draper, N.; Ferraz Leal, R.; Gigg, M. A.; Lynch, V. E.; Markvardsen, A.; Mikkelson, D. J.; Mikkelson, R. L.; Miller, R.; Palmen, K.; Parker, P.; Passos, G.; Perring, T. G.; Peterson, P. F.; Ren, S.; Reuter, M. A.; Savici, A. T.; Taylor, J. W.; Taylor, R. J.; Tolchenov, R.; Zhou, W.; Zikovsky, J.
  Nuclear Instruments & Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment (2014), 764 (), 156-166CODEN: NIMAER; ISSN:0168-9002. (Elsevier B.V.)
  The Mantid framework is a software soln. developed for the anal. and visualization of neutron scattering and muon spin measurements. The framework is jointly developed by software engineers and scientists at the ISIS Neutron and Muon Facility and the Oak Ridge National Lab. The objectives, functionality and novel design aspects of Mantid are described.
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37. 37
  Könnecke, M.; Akeroyd, F. A.; Bernstein, H. J.; Brewster, A. S.; Campbell, S. I.; Clausen, B.; Cottrell, S.; Hoffmann, J. U.; Jemian, P. R.; Männicke, D.; Osborn, R.; Peterson, P. F.; Richter, T.; Suzuki, J.; Watts, B.; Wintersberger, E.; Wuttke, J. The NeXus Data Format. J. Appl. Crystallogr. 2015, 48, 301– 305, DOI: 10.1107/S1600576714027575
  37
  The NeXus data format
  Konnecke Mark; Akeroyd Frederick A; Cottrell Stephen; Bernstein Herbert J; Brewster Aaron S; Campbell Stuart I; Peterson Peter F; Clausen Bjorn; Hoffmann Jens Uwe; Jemian Pete R; Mannicke David; Osborn Raymond; Richter Tobias; Suzuki Jiro; Watts Benjamin; Wintersberger Eugen; Wuttke Joachim
  Journal of applied crystallography (2015), 48 (Pt 1), 301-305 ISSN:0021-8898.
  NeXus is an effort by an international group of scientists to define a common data exchange and archival format for neutron, X-ray and muon experiments. NeXus is built on top of the scientific data format HDF5 and adds domain-specific rules for organizing data within HDF5 files, in addition to a dictionary of well defined domain-specific field names. The NeXus data format has two purposes. First, it defines a format that can serve as a container for all relevant data associated with a beamline. This is a very important use case. Second, it defines standards in the form of application definitions for the exchange of data between applications. NeXus provides structures for raw experimental data as well as for processed data.
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38. 38
  Hammouda, B. SANS from Homogenous Polymer Mixtures - a Unified Overview. Adv. Polym. Sci. 1993, 87– 133, DOI: 10.1007/BFb0025862
  38
  SANS from homogeneous polymer mixtures: a unified overview
  Hammouda, Boualem
  Advances in Polymer Science (1993), 106 (Polymer Characteristics), 87-133CODEN: APSIDK; ISSN:0065-3195.
  A review with 45 refs. on various modeling methods used to understand small-angle neutron scattering (SANS) data from homogeneous polymer systems.
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39. 39
  De Gennes, P. Pierre-Giles De Gennes - Scaling Concepts in Polymer Physics; Cornell University Press - Libgen.Lc.Pdf.1979, p 324.
  There is no corresponding record for this reference.
40. 40
  Hammouda, B. Form Factors for Branched Polymers with Excluded Volume. J. Res. Natl. Inst. Stand. Technol. 2016, 121, 139– 164, DOI: 10.6028/jres.121.006
  40
  Form Factors for Branched Polymers with Excluded Volume
  Hammouda Boualem
  Journal of research of the National Institute of Standards and Technology (2016), 121 (), 139-164 ISSN:1044-677X.
  The form factors for star-branched polymers with linear branches or with looping branches are calculated. The effect of chain swelling excluded volume is incorporated through an excluded volume parameter approach. The form factor for ring polymers is also included, since it is nicely derived as a special case. Furthermore, the form factor for dendrimers with excluded volume is also calculated. In order to evaluate the form factor for stars with looping branches, the multivariate Gaussian function is used to close the looping branches. Analytical results are possible in the Gaussian chain case (i.e., with no excluded volume), but the calculations are left in a form involving summations over monomers when the general case incorporates excluded volume.
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41. 41
  Nedoma, A. J.; Robertson, M. L.; Wanakule, N. S.; Balsara, N. P. Measurements of the Composition and Molecular Weight Dependence of the Flory-Huggins Interaction Parameter. Macromolecules 2008, 41, 5773– 5779, DOI: 10.1021/ma800698r
  41
  Measurements of the Composition and Molecular Weight Dependence of the Flory-Huggins Interaction Parameter
  Nedoma, Alisyn J.; Robertson, Megan L.; Wanakule, Nisita S.; Balsara, Nitash P.
  Macromolecules (Washington, DC, United States) (2008), 41 (15), 5773-5779CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
  The phase behavior of binary blends of polyolefins is studied using small-angle neutron scattering. Component 1 is polyisobutylene (PIB), and component 2 is deuterated polybutadiene (dPB). Blends of these polymers are known to exhibit lower crit. soln. temps. The scattering intensity profiles from homogeneous PIB/dPB blends are fit to the RPA to det. χ, the Flory-Huggins interaction parameter. We demonstrate that χ depends on temp., blend compn., and component mol. wts.
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42. 42
  Sarasua, J. R.; Arraiza, A. L.; Balerdi, P.; Maiza, I. Crystallinity and Mechanical Properties of Optically Pure Polylactides and Their Blends. Polym. Eng. Sci. 2005, 45, 745– 753, DOI: 10.1002/pen.20331
  42
  Crystallinity and mechanical properties of optically pure polylactides and their blends
  Sarasua, J. R.; Arraiza, A. Lopez; Balerdi, P.; Maiza, I.
  Polymer Engineering and Science (2005), 45 (5), 745-753CODEN: PYESAZ; ISSN:0032-3888. (John Wiley & Sons, Inc.)
  Nonisothermal solidifications of medical-grade polylactides were conducted on compression molding sheets, resulting in a variety of cryst. forms and different amts. of crystallinity. Both optically pure polylactides, poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA), were found to crystallize at a low melting temp. α cryst. form. PLLA/PDLA blends were found to yield both α homocrystallites and 50°C higher melting temp. stereocomplex crystallites. The effects of processing conditions and blend compn. on crystal heterogeneity and degree of crystallinity were studied. Tensile tests reveal for these polylactides Young's modulus values of 3.5-4.2 GPa, strength values of 62-71 MPa, and elongations at break of 1-5%, depending on blend compn. and crystallinity.
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43. 43
  Tashiro, K.; Kouno, N.; Wang, H.; Tsuji, H. Crystal Structure of Poly(Lactic Acid) Stereocomplex: Random Packing Model of PDLA and PLLA Chains As Studied by X-Ray Diffraction Analysis. Macromolecules 2017, 50, 8048– 8065, DOI: 10.1021/acs.macromol.7b01468
  43
  Crystal Structure of Poly(lactic acid) Stereocomplex: Random Packing Model of PDLA and PLLA Chains As Studied by X-ray Diffraction Analysis
  Tashiro, Kohji; Kouno, Naoto; Wang, Hai; Tsuji, Hideto
  Macromolecules (Washington, DC, United States) (2017), 50 (20), 8048-8065CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
  The crystal structure model of stereocomplex between poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA) with the L/D ratio of 50/50 was proposed by several groups [the space group P1 model by Okihara et al. (1991) and R3c or R‾3c model by Cartier et al. (1997)], among which the model of the space group R3c (or R‾3c) had been currently recognized as the most preferable one. However, the thus apparently established model cannot explain such an important exptl. fact that the stereocomplex is formed not only for the PLLA/PDLA blend of the L/D ratio 50/50 but also for the blends with the L/D ratio of 70/30-30/70. We have proposed here a new model with the space group P3, which can cover the SC structures of the L/D ratio in the range of 70/30-50/50-30/70. This model can show the more quant. reproducibility of the obsd. X-ray diffraction data for both the hkl and 000l reflection profiles. In particular the exptl. observation of the 0003 reflection is inconsistent with the previous model of the space group R3c, which requests the appearance of only the 000l with l = 6, 12, etc. In the newly proposed P3 model the mol. chains take the regular (3/1) helical conformation; however, the packing mode is not regular. The unit cell consists of the statistically disordered arrangement of the right-handed (R) and left-handed (L) chains of the upward (u) or downward (d) directionality. For example, in the case of the stereocomplex with L/D ratio 70/30, a pair of the left-handed downward (Ld) and right-handed upward (Ru) chains is located at one lattice site at the statistical occupancy of 70/30 ratio and another pair of the left-handed upward (Lu) and right-handed downward (Rd) chains is at the adjacent lattice site at the same 70/30 ratio. The unit cell contains the three sets of these two pairs, which are connected to each other by the sym. relation of the 3-fold rotation axis. The proposed statistical packing model of the upward and downward chains can explain such various observations as the spherulite formation or the existence of the lamellae with the chain folding structure in the spherulite, the solvent-induced change from the stereocomplex to the α form, and so on.
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44. 44
  Van De Witte, P.; Dijkstra, P. J.; Van Den Berg, J. W. A.; Feijen, J. Phase Behavior of Polylactides in Solvent-Nonsolvent Mixtures. J. Polym. Sci. Part B 1996, 34, 2553– 2568, DOI: 10.1002/(SICI)1099-0488(19961115)34:15<2553::AID-POLB3>3.0.CO;2-U
  44
  Phase behavior of polylactides in solvent-nonsolvent mixtures
  van de Witte, P.; Dijkstra, P. J.; van den Berg, J. W. A.; Feijen, J.
  Journal of Polymer Science, Part B: Polymer Physics (1996), 34 (15), 2553-2568CODEN: JPBPEM; ISSN:0887-6266. (Wiley)
  Isothermal phase diagrams for the semicryst. poly-L-lactide (PLLA) and the amorphous poly-DL-lactide (PDLLA) in combination with several solvent-nonsolvent combinations (dioxane/water, dioxane/methanol, chloroform/methanol, and NMP/water) have been detd. The locations of the liq.-liq. miscibility gap, the solid-lipid miscibility gap and the vitrification boundary in the isothermal phase diagrams at 25°C were identified. The liq.-liq. miscibility gap for the systems with PLLA was located in the same compn. range as the corresponding systems with PDLLA. For the systems contg. PLLA solid-liq. demixing was thermodynamically preferred over liq.-liq. demixing. Attempts were made to correlate the exptl. findings with predictions on the basis of the Flory-Huggins theory for ternary solvents using interaction parameters derived from independent expts. Qual. agreement was found between the theor. predictions and the exptl. obtained liq.-liq. miscibility gap. No good agreement was found for the solid-liq. miscibility gap.
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45. 45
  Antoine, S.; Geng, Z.; Zofchak, E. S.; Chwatko, M.; Fredrickson, G. H.; Ganesan, V.; Hawker, C. J.; Lynd, N. A.; Segalman, R. A. Non-Intuitive Trends in Flory-Huggins Interaction Parameters in Polyether-Based Polymers. Macromolecules 2021, 54, 6670– 6677, DOI: 10.1021/acs.macromol.1c00134
  45
  Non-intuitive Trends in Flory-Huggins Interaction Parameters in Polyether-Based Polymers
  Antoine, Segolene; Geng, Zhishuai; Zofchak, Everett S.; Chwatko, Malgorzata; Fredrickson, Glenn H.; Ganesan, Venkat; Hawker, Craig J.; Lynd, Nathaniel A.; Segalman, Rachel A.
  Macromolecules (Washington, DC, United States) (2021), 54 (14), 6670-6677CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
  Recently, a variety of "click" or other additive chemistries have been introduced to functionalize polymers after polymn. to target specific applications, for example, membranes, catalysis, or drug delivery systems. It is generally assumed that the inclusion of these "click" linking groups has minimal impact on the thermodn. of the polymer as a whole. In this study, we demonstrate that the introduction of these click-derived units has a profound impact on the Flory-Huggins parameter of polyether derivs. Using RPA fits for small-angle X-ray scattering data from block copolymer pairs to est. the Flory-Huggins interaction parameter (χ), we detd. that poly(ethylene oxide) (PEO) and poly(allyl glycidyl ether) (PAGE), which differ only by the inclusion of an allyl sidechain, have a χ of 0.030 (at T = 34°C). While PEO is miscible with poly(lactide) (PLA) at nearly all temps., the PLA/PAGE χ detd. exptl. is 0.015 (at T = 30°C). Atomistic mol. dynamics simulations of PEO/PAGE oligomer blends show that upon blending, PEO chains contract and move closer together, while PAGE chains stretch and spread apart, indicating an enthalpic contribution to the χ parameter due to changes in polymer coordination resulting from the conformational asymmetry of PAGE and PEO. These studies demonstrate the large impact that functionalization and side-chain units have on the χ parameter of polymer pairs.
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Supporting Information
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.macromol.2c02020.
- Information about materials and methods used to synthesize the polymers analyzed in this work, as well as characterization data for the cyclic and linear polymers (such as MALDI-TOF spectra); further data from SANS experiments, such as some intensity vs q plots not included in this manuscript and R_g values for key samples (PDF)
- ma2c02020_si_001.pdf (493.94 kb)
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Comparison of Cyclic and Linear Poly(lactide)s Using Small-Angle Neutron ScatteringClick to copy article linkArticle link copied!

Macromolecules

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Abstract

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Introduction

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Materials and Methods

Synthetic Procedures

Cyclic Poly(rac-lactide)

Linear Poly(lactide)

SANS Measurements

RPA Analysis of SANS Data

Results and Discussion

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Conclusions

Supporting Information

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Acknowledgments

References

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Abstract

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References

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Comparison of Cyclic and Linear Poly(lactide)s Using Small-Angle Neutron Scattering
Click to copy article linkArticle link copied!