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Unraveling the Influence of the Preexisting Molecular Order on the Crystallization of Semiconducting Semicrystalline Poly(9,9-di-n-octylfluorenyl-2,7-diyl (PFO)
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Unraveling the Influence of the Preexisting Molecular Order on the Crystallization of Semiconducting Semicrystalline Poly(9,9-di-n-octylfluorenyl-2,7-diyl (PFO)
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  • Valentina Pirela
    Valentina Pirela
    POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry, and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián20018, Spain
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  • Mariano Campoy-Quiles
    Mariano Campoy-Quiles
    Institute of Materials Science of Barcelona, ICMAB-CSIC, Campus UAB, Bellaterra08193, Spain
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    Orcidhttps://orcid.org/0000-0002-8911-640X
  • Alejandro J. Müller*
    Alejandro J. Müller
    POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry, and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián20018, Spain
    IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5, Bilbao48009, Spain
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0001-7009-7715
  • Jaime Martín*
    Jaime Martín
    POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry, and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián20018, Spain
    IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5, Bilbao48009, Spain
    Universidade da Coruña, Campus Industrial de Ferrol, CITENI, Esteiro, Ferrol15403, Spain
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0002-9669-7273
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Chemistry of Materials

Cite this: Chem. Mater. 2022, 34, 23, 10744–10751
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https://doi.org/10.1021/acs.chemmater.2c02917
Published November 23, 2022

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Abstract

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Understanding the complex crystallization process of semiconducting polymers is key for the advance of organic electronic technologies as the optoelectronic properties of these materials are intimately connected to their solid-state microstructure. These polymers often have semirigid backbones and flexible side chains, which results in a strong tendency to organize/order in the liquid state. Therefore, crystallization of these materials frequently occurs from liquid states that exhibit─at least partial─molecular order. However, the impact of the preexisting molecular order on the crystallization process of semiconducting polymers─ indeed, of any polymer─remained hitherto unknown. This study uses fast scanning calorimetry (FSC) to probe the crystallization kinetics of poly(9,9-di-n-octylfluorenyl-2,7-diyl (PFO) from both an isotropic disordered melt state (ISO state) and a liquid-crystalline ordered state (NEM state). Our results demonstrate that the preexisting molecular order has a profound impact on the crystallization of PFO. More specifically, it favors the formation of effective crystal nucleation centers, speeding up the crystallization kinetics at the early stages of phase transformation. However, samples crystallized from the NEM state require longer times to reach full crystallization (during the secondary crystallization stage) compared to those crystallized from the ISO state, likely suggesting that the preexisting molecular order slows down the advance in the latest stages of the crystallization, that is, those governed by molecular diffusion. The fitting of the data with the Avrami model reveals different crystallization mechanisms, which ultimately result in a distinct semicrystalline morphology and photoluminescence properties. Therefore, this work highlights the importance of understanding the interrelationships between processing, structure, and properties of polymer semiconductors and opens the door for performing fundamental investigations via newly developed FSC methodologies of such materials that otherwise are not possible with conventional techniques.

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Introduction

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Motivated by the promise of low-cost production of conformable electronic devices, for example, organic solar cells, organic light-emitting diodes, thermoelectric modules, and organic electrochemical transistors, and so forth, semiconducting polymers are attracting great interest from both academic and industrial sectors. The operation of these devices is typically based on the optical and electrical properties of semiconducting polymer thin films, which are known to be intimately connected to their solid-state microstructure. More specifically, properties such as the mobility of charge carriers (either electronic or ionic) and the absorption and emission of light are profoundly affected by the presence of molecular domains with a structural order, for example, crystals, in the material, (1−4) simply because they exhibit a greater overlap of π-orbitals and a reduced energetic disorder compared to amorphous/disordered domains. Consequently, the control over optical and electrical properties of polymer semiconductors─and hence, rational optimization of devices─stems from a precise understanding and control of their solid-state microstructure.
The solid-state microstructure of many semiconducting polymers is generated via crystallization in the thin film deposition step. Thus, gaining an understanding of how crystallization is developed is of paramount importance to establishing accurate processing-structure–property relationships. However, fundamental investigations of the crystallization process are scarce in the literature and are limited to congeners of the polythiophene family. (5−13) As a result, many important questions about the crystallization of semiconducting polymers remain unanswered.
Among these, one of the most important questions is how preexisting molecular order in the liquid state impacts crystallization and solid-state microstructure development. Due to the rigidity of aromatic backbones and their amphiphilic nature, many high-performing, crystallizable semiconducting polymers exhibit liquid-crystalline behavior; therefore, crystallization in these polymers likely occurs via the stacking of polymer chain segments that exhibit a preexisting order in the liquid state. (14−17) Moreover, even nonliquid-crystalline polymer semiconductors are known to exhibit a strong tendency to form aggregates with local molecular order prior to crystallization. (17−21) Therefore, a major fundamental question in the field remains as to whether or not (and if so, how) the crystallization process of semiconducting polymers is affected by the presence of molecular order in the liquid state.
Crystallizable main-chain liquid-crystalline semiconducting polymers seem ideal material systems to investigate this scientific problem as (i) they can crystallize and (ii) exhibit both ordered and disordered liquid phases. However, because the liquid phase that is thermodynamically stable at temperatures immediately above the crystallization temperature is the liquid-crystalline mesophase, these materials have a strong tendency to crystallize solely from the ordered mesophase. Conversely, the crystallization from the isotropic phase is strongly hampered in these materials. Most likely due to this experimental difficulty, the effect of the preexisting molecular order of an isotropic melt on the crystallization of polymers has been largely unexplored, not just for semiconducting polymers but also for polymers in general. (10,12,22−28)
Fortunately, the above-mentioned experimental difficulties in investigating crystallization from the isotropic phase may be overcome with advanced thermal characterization methods, such as fast scanning calorimetry (FSC). The extremely fast heating and cooling ramps (up to ∼ 104 °C/s) that can be applied in FSC are opening a plethora of new possibilities to investigate materials’ thermal phase transitions, including those previously nonaccessible. For example, potentially, one can design thermal treatments aimed at suppressing liquid-crystalline mesophases (at temperatures slightly above crystallization temperature) so that liquid-crystalline polymers can be crystallized from a disordered, isotropic liquid state.
To explore the hypothesis above, we selected poly(9,9-di-n-octylfluorenyl-2,7-diyl (PFO) as a model material system. PFO is a well-known crystallizable semiconducting polymer with relatively low thermal transition temperatures. Therefore, suitable thermal protocols can be designed to minimize the risk of significant degradation issues. (21) In addition to─at least─two crystalline forms, PFO exhibits a nematic liquid-crystalline mesophase (hereafter referred to as the NEM state) in the temperature range immediately above the crystalline phase(s) along with an isotropic liquid phase (hereafter referred to as ISO state) at higher temperatures. (11,13,21,22,29−31)
Hence, in this paper, we unravel the impact of the preexisting molecular order on the isothermal crystallization kinetics of the semiconducting polymer PFO, which allows us to rationalize the resulting solid-state microstructure and the optical response (photoluminescence) of the solid material. We discover that the effect of the molecular order on crystallization is complex: the kinetics of the early stages of crystallization is faster when crystallization occurs from the ordered liquid state, likely because the preexisting molecular order facilitates crystal nucleation. However, liquid-crystalline order seems to slow down the advance of the later stages of the crystallization, that is, those governed by molecular diffusion, likely because the chain segments diffusing to the growing crystal front must distort the ordered molecular arrangement in the liquid mesophase, which has an associated free-energy penalty. The different crystallization kinetics result in a distinct dimensionality of the crystallization, which yields different crystal morphologies and, ultimately, a different optical response (photoluminescence) in the semiconducting solid material.

Experimental Section

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Materials

The PFO sample was donated to us by the group of De Mello and used without further purification. (29) The polymer had a number-average molecular weight (Mn) of 13.04 kDa, and the dispersity (D̵) was 2.03, as determined by size exclusion chromatography in combination with multiangle light scattering (SEC-MALS) and size exclusion chromatography calibrated with polystyrene (SEC-PS), respectively. THF was purchased from Sigma-Aldrich and used without further purification. PFO thin films were prepared by placing a drop of glucose solution directly on the reference part on the backside of the chip sensor. Then, a 10 mg/mL solution of PFO in THF was deposited by spin coating (2,000 rpm, 60 s) onto the FSC chip sensor. Finally, the glucose drop is removed carefully with water.

Fast Scanning Chip Calorimetry

Fast scanning chip (FSC) calorimetry experiments were performed on a Mettler-Toledo Flash DSC 2 + device. The equipment is connected to a Huber TC-100 intracooler, permitting scans of up to 40,000 °C/s. The MultiSTAR UFS1 (24 × 24 × 0.6 mm3) chip sensors were conditioned and corrected prior to use according to the Flash DSC 2 + specifications. Measurements were carried out under a nitrogen atmosphere, with a constant flow rate of 80 mL/min. The STARe software was used to analyze the data. The thermal protocols essentially consisted in recording heat flow rates during the heating of the sample crystallized at a given temperature at different times. Unless otherwise specified, note that the selected heating and cooling rates for FSC used in this paper were 4000 °C/s. It is important to notice that for FSC measurements, the sample mass is in the nanoscale magnitude. The same sensor was used for all crystallization experiments. Hence, the sample size remained constant.

Atomic Force Microscopy

A dimension ICON with a Nanoscope V controller (Bruker) atomic force microscopy (AFM) was used to image the samples. A Peak-Force tapping mode using ScanAsyst-Air tips by Bruker (nominal tip radius of 2 nm, nominal frequency of 70 kHz, nominal spring constant = 0.4 N/m) was used to obtain the images. A PFO thin film was deposited from a 10 mg/mL solution on the back side of the chip with a glucose cover on the reference cell, which was removed after deposition with water. The sample was heated above the nematic-to-isotropic transition (TLC-I), and after melting, it was rapidly cooled (at 4,000 °C/s) to the annealing temperature (Ta). Subsequently, the sample was kept at Ta for 10 h (the time it reaches maximum saturation), it was rapidly cooled to a temperature below the glassy state, Tg, and rapidly heated to room temperature and then measured by AFM.

Photoluminescence Spectroscopy

Photoluminescence spectra were measured using Witec equipment. We excited it through a UV high transmission 40× objective using a solid-state laser with a peak wavelength at 355 nm, with a power of 60 μW. We made 500 μm × 500 μm images of the samples directly on the FSC sensor chips. We took a total of 2500 spectra per sample. Cluster analysis of the data revealed three different regions for each chip: (i) the inner part, likely very thick as deduced from the apparent self-absorption features in the spectra; (ii) the region above the heating resistance; (iii) the border between both. The data shown in the article corresponds to the material fraction just over the resistances. A PFO thin film was deposited from a 10 mg/mL solution on the back side of the chip with a glucose cover, after deposition, the drop was eliminated with water. The sample was heated above TLC-I to erase the thermal history and then rapidly cooled (at 4,000 °C/s) from the melt to the selected isothermal crystallization temperature. Subsequently, the sample was kept at Ta for 10 h (the time it reaches maximum saturation), and it was rapidly cooled to a temperature below Tg and rapidly heated to room temperature.

Results and Discussion

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Establishment of Suitable Thermal Protocols for the Study

Prior to our investigation, we wanted to scrutinize the possibility of crystallizing PFO from the disordered ISO state by cooling the meltdown from a temperature above the nematic-to-isotropic transition (TLC-I) (29) to the crystallization temperature, employing cooling rates like those typically applied in regular differential scanning calorimetry (DSC) or polarized-light optical microscopy (PLOM) experiments, namely, <100 °C/min. However, our data (included in Figure 1S of the Supporting Information) unambiguously proved that this range of cooling rates does not suffice to avoid the formation of the liquid-crystalline mesophase during cooling. Hence, in full accordance with our initial premises, conventional DSC and PLOM are not suitable for these studies, and methods enabling faster cooling rates, such as FSC, need to be used instead.
Thus, we started our study by investigating the thermal conditions that allow us to compare crystallizations from the ISO and NEM states. More specifically, we need first to gain knowledge of the thermotropic phase behavior of PFO, including phase transition temperatures, and, secondly, to figure out the temperature range that allows isothermal crystallization from both the ISO state and the NEM state.
Figure 1A shows the FSC thermal protocol used to assess the thermotropic landscape of PFO. First, PFO samples were heated to a temperature well above the TLC-I transition to erase any thermal history (e.g., at 300 °C). Then, samples are rapidly cooled down (at 4000 °C/s) to various isothermal temperatures, Ta, ranging from 40 to 160 °C, and kept there for 1 h. During these isothermal steps, the PFO material will evolve according to its thermodynamic nature at that Ta. The evolution suffered by the material at each Ta is probed in a subsequent heating scan (performed at 4,000 °C/s, identified as an “Analysis scan”).

Figure 1

Figure 1. Thermotropic phase behavior of PFO. (A) Thermal protocol employed for the experiment. Relevant temperatures: annealing temperature, Ta, glass transition temperature, Tg, melting temperature, Tm, and nematic-to-isotropic transition temperature, TLC-I. (B) FSC heating traces (at 4000 °C/s) following the isothermal step of 1 h at temperatures ranging from Ta = 40 to 160 °C. Endothermic peaks shadowed in purple-cyan and orange correspond to the enthalpic relaxation of the glassy phase, the melting of crystals, and the nematic–isotropic transition, respectively.

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Figure 1B displays the calorimetric traces corresponding to the heating scans mentioned above (i.e., “Analysis scan”). The Ta applied in the experiments is indicated on the right-hand side of the curves. Three different endothermic processes can be distinguished in the heating traces depending on the Ta applied. An aging glass tends to evolve toward an equilibrium state at temperatures well below their Tg. Hence, the area of the physical aging endotherm will decrease as the annealing temperature, Ta, increases, and approaches Tg. Based on this, below Ta = 80 °C, a broad endotherm at low annealing temperatures (Ta < 80 °C) is observed. The area of this endotherm decreases with increasing annealing temperature, indicating that PFO is below Tg. That is, the observed endothermic peaks below Ta = 80 °C correspond to the enthalpic overshoot as a physically aged glass undergoes the glass transition (this peak is shadowed in purple in Figure 1B). Moreover, in cyan color, at temperatures between Ta = 80 and 150 °C, the overshoot due to the physical aging is no longer visible, and instead, a sharp bell-shaped endotherm associated with the melting process of the crystallites formed during the isothermal steps is observed. (32−34)
Finally, the endothermic peaks colored in orange, from Ta = 90 °C onward, feature the nematic-to-isotropic transition. Hence, this experiment directly informs about the thermodynamic phase behavior of the material, including relevant transition temperatures.
The experiment above demonstrates that the crystallization of PFO occurs between Ta = 80 and Ta = 140 °C. Interestingly, curves obtained for Tas between 80 °C and below 90 °C feature solely the peak due to the melting of crystals, suggesting that no nematic phase forms during the isothermal steps of 1 h at those temperatures. In other words, the crystallization of PFO at Ta = 80 °C occurs from the ISO state when samples are cooled down from 300 to 80 °C at 4000 °C/s.
However, an isothermal step of 1 h is typically a short period for the crystallization of polymers to complete at temperatures so close to Tg. Therefore, to identify a suitable temperature range for our study, that is, the temperature range where crystals can develop from the ISO state, longer crystallization times need to be explored, for example, 10 h. Shown in Figure 2SA,C and E of the Supporting Information are the calorimetric heating traces after samples were isothermally crystallized for 10 h at Tas of 80, 82, and 85 °C. As can be observed, neither of those traces exhibits the endothermic peak associated with TLC-I, proving that PFO crystallizes solely from the ISO state between Ta = 80 and Ta = 85 °C after being cooled down at 4000 °C/s from 300 °C.
Therefore, a suitable thermal protocol to investigate the crystallization of PFO from the ISO state is shown in Figure 2A. The samples are first heated above TLC-I to erase the thermal history for a short amount of time of 1 s to avoid degradation. Then, samples are rapidly cooled down (at 4000 °C/s) to the selected Ta (between 80 and 85 °C), where it is kept for a variable amount of time so that crystallization progresses. Samples are then rapidly cooled down to a temperature below Tg (at 4000 °C/s), and lastly, they are heated to 300 °C (at 4000 °C/s) for 1 s. The endothermic peak appearing in this heating scan accounts for the melting of crystals formed during the isothermal step; hence, the enthalpy of this melting process can be employed to follow the isothermal crystallization kinetics. It is customary to assume that the values of melting enthalpy (measured under nonisothermal conditions, i.e., during the heating scans after isothermal crystallization) are identical to the values of the crystallization enthalpy developed under isothermal conditions.

Figure 2

Figure 2. Crystallization from an ISO state (left column) and from a NEM state (right column) for varying times. (A and B) Thermal protocols used, where Ta is the annealing temperature, TLC is the temperature at which the liquid crystal develops, Tm is the melting temperature, t is the annealing time, and tsat is the annealing time when the degree of crystallization reaches saturation. (C and D) FSC heating traces (analysis scans); the progression of time is illustrated by the color scale inside the arrow. (E and F) Advance of crystallization (from normalized enthalpy values) with time at the indicated temperatures and their corresponding Avrami fits. t and to are the annealing time and the induction time, respectively.

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Having established the thermal conditions to investigate the isothermal crystallization of PFO from the ISO state, we determined a suitable thermal treatment to assess crystallization from the NEM state between Ta = 80 and 85 °C. The NEM state can in principle, develop at any temperature above the Tm, but the higher the annealing temperature, the faster the development of the NEM state. However, high temperature also prompts undesired thermal degradation processes; hence, we tried to minimize the exposure of samples to high temperatures. We found out that the PFO NEM state adequately formed when samples were first crystallized, and then crystals were molten without overpassing TLC-I. Thus, the thermal protocol to study the crystallization of PFO from the nematic mesophase included two steps (Figure 2B): (i) an initial step in which the mesophase is formed (PFO is crystallized at Ta = 80 °C for 30 min and then taken to 160 °C for 1 min) and (ii) a second step that is equal to the one employed for the crystallization of samples from the ISO state.

Isothermal Crystallization Kinetics from the Isotropic and the Nematic Liquid States

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Once we established the temperature conditions for our crystallization experiments, we endeavored to investigate the overall crystallization kinetics from the disordered ISO state and the ordered NEM state.
Because polymer crystallization usually proceeds by nucleation and growth, it can be readily modeled with the Avrami framework, which describes the free growth of objects from random nucleation centers. The model yields the expression below (eq 1). (35,36)
1−Vc(t−to)=exp(−k(t−to)n)
(1)
where Vc is the relative volumetric transformed fraction to the crystalline state, t is the crystallization time, to is the induction time, k is the overall crystallization rate constant which includes nucleation and growth components, and n is the Avrami index. (35,36) Moreover, Vc can be expressed as a function of the mass fraction of the samples (Wc) as seen in eq 2.
Vc=WcWc+(ρcρa)(1−Wc)
(2)
where Wc is the mass fraction of the sample, ρc is the density of a 100% crystalline sample, and ρa is the density of a 100% amorphous sample. The values of ρc and ρa are unknown for PFO, and therefore, we cannot apply eq 1 in terms of volume fraction. However, Vc is proportional to Wc (see equations 2 and 3) and the overall crystallization kinetics determined by DSC can be fitted to the Avrami equation in terms of the mass fraction of crystals as an approximation. From eq 3, ΔH(t) is the enthalpy at a given crystallization temperature, and ΔHtotal is the maximum enthalpy value reached at the end of the isothermal crystallization process. The enthalpies are obtained from the specific heat capacity (Cp) as a function of mass. These values are obtained from the normalized integrated area of each peak divided by the scan rate to determine the relative crystallinity mass fraction of the sample at a given t and describe the kinetics of the material at a constant mass.
Wc=ΔH(t)ΔHtotal
(3)
Moreover, Müller et al. (37,38) proposed that the Avrami index (n) can be considered in terms of the addition of two components: a nucleation rate component (nn) and a growth dimensionally (nd) component (eq 4). (35,36)
n=nn+nd
(4)
where nd can have values of 1, 2, and 3 depending on the dimensionality of the crystalline ensembles formed [i.e., needles (1D), axialites (2D), and spherulites (3D)]. The nn value is proportional to the rate of nucleation with values ranging from 0 to 1; values equal to 1 are due to sporadic nucleation, whereas values equal to 0 represent instantaneous nucleation.
Figure 2C,D shows the heating traces employed for the study of the crystallization kinetics (denoted as “Analysis scan” in Figure 2A,B). For clarity, experimental data obtained at a Ta of 80 °C is the only one shown here, while data for the rest of the crystallization temperatures are included in the Supporting Information (Figure 2S).
In order to study the crystallization kinetics, the crystal melting peaks were integrated, and the resulting enthalpy (normalized to the final value) was plotted against the crystallization time (Figure 2E,F). We note here too that the heating curves of PFO crystallized from the ISO state displayed a single endothermic feature associated with the crystal melting while those of PFO crystallized from the NEM state exhibited a further peak associated with TLC-I transition.
As Ta increases, the overall crystallization rate becomes slower. This is reflected in a shift of the curves to higher crystallization times as Ta increases. In addition, the nucleation rate (1/to) when crystallizing from an ISO state decreases with increasing Ta. To represents the induction time before any crystallization can be detected by the calorimeter; hence, its inverse is proportional to the primary nucleation rate. Therefore, a decrease in 1/to indicates that the rate of nucleation becomes slower with increasing Ta. Values of 1/to can be found in Table 1S of the Supporting Information.
Interestingly, the comparison of 1/to values for crystallizations from the ISO state and the NEM state at the same temperature reveals that the preexisting molecular order in the crystallizing PFO liquid accelerates the formation of effective nucleation centers. A faster nucleation process can explain why a faster overall crystallization rate is observed in the sample crystallized from the NEM state both at 20% conversion (1/τ20%) and at 50% conversion (1/τ50%) (see Table 1S of the Supporting Information).
It is important to note that samples crystallized from the NEM state require longer times to reach the fully relative crystallized state in the sample, likely suggesting that the liquid-crystalline order slows down the advance of the later stages of the crystallization, that is, those governed by molecular diffusion, after the crystallites impinged on one another during the growth process (i.e., during the secondary overall crystallization process that typically occurs at relative conversions to the semicrystalline state larger than 50%).
We should consider that in the process of polymer crystallization, nucleation and mostly free growth from the activated nuclei first take place, and the overall crystallization kinetics accelerates with time (during the so-called primary crystallization). Then, a point is reached at which the kinetics slow down because the growing superstructures [spherulites or axialites, which are semicrystalline entities or lamellar aggregates with three and two dimensions containing amorphous (molten) chains in between them] impinge on one another. This point usually coincides with or is close to 50% conversion to the semicrystalline state and is close to the time to peak when examining isothermal crystallization enthalpy values as a function of time. Secondary crystallization starts at this point when intraspherulitic (or axialitic) and interspherulitic material has not yet crystallized. If we crystallize from a preordered state (i.e., the nematic state), the energy barrier for overall primary crystallization (which includes both nucleation and growth) will most probably be lower than that needed to crystallize from the isotropic melt. We argue that the primary crystallization is dominated by nucleation when it occurs from the nematic state, and the overall crystallization kinetics is accelerated, thanks to the enhanced nucleation with respect to the isotropic state. Then, during secondary crystallization, as amorphous chains are embedded in between the already-formed crystallites, the diffusion rates are usually much lower than during primary crystallization and the effect of nucleation at this stage can almost be neglected.
The NEM state exhibits orientational order but lacks the positional order that the crystalline motif has. Therefore, the crystallization of polymer molecules within the NEM state must concur with some kind of translational motion that requires molecular or─at least─segmental relaxation. The slower kinetics is thus consistent with the fact that chain segments diffusing to the growing crystal front must distort the ordered molecular arrangement of the NEM state, which has an associated free-energy penalty. We must highlight, moreover, that our isothermal crystallization data from in situ wide-angle X-ray scattering (WAXS), included in the Supporting Information (Figure 3S and Table 2S), agree well with the above-mentioned results and conclusions. Clearly, a realistic dynamic microscopic picture─at the molecular level─of how a polymer molecule within the nematic mesophase transits into the crystalline state is required to fully understand the crystallization of PFO polymer.
To gain further information about the crystallization kinetics, experimental data were fitted with the Avrami model (dashed lines in Figure 2E,F). The resulting Avrami parameters are given in Table S1 found in the Supporting Information and plotted in Figure 3. We must note that the Avrami theory is used to describe the primary crystallization range (during the free growth of crystals without any impingement of one another), and fittings for large crystallization conversions are often unsuitable. Hence, to ensure the free growth approximation, the conversion range employed for the fittings was 3–20% of the relative crystallization conversion.

Figure 3

Figure 3. Experimental results and Avrami parameters as a function of crystallization temperature. (A) Experimental values of the inverse of crystallization times (1/τ50% and 1/τ20%) for different conversions, (B) Avrami index (n), (C) Specific heat capacity for the longest crystallization time times the mass (Cp·m) (i.e., a proxy for the final degree of crystallinity because m is kept constant in the entire experiment), and (D) isothermal crystallization rate obtained from the Avrami model (k1/n).

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The values obtained for 1/τ20% by fitting the Avrami theory at 20% conversion are excellent matches to the corresponding experimental values. Hence, as expected, the Avrami theory describes the primary crystallization range very well. However, in the case of 50% conversion, the rate values are overestimated and do not correspond with the experimental values, probably indicating the earlier impingement of crystals in the interval between 20 and 50% conversion, which produces unrealistic fittings at conversions higher than 20%. These deviations of the experimental data from the Avrami fit can be clearly observed in Figure 2E,F.
Figure 3B shows how the Avrami index (n) varies with Ta values depending on the initial liquid state, that is, ISO state versus NEM state. The Avrami index was found to be larger at lower Ta values for crystallization from the ISO state. At Ta = 80 °C, there is a significant change from n = 1.7 when the PFO is crystallized from the melt state to 1.1 when it is crystallized from the NEM state. That is, the Avrami parameter is closer to 2 for the crystallization from an ISO state and to 1 from a NEM state. One way to interpret these results is a change in the morphology and nucleation of the PFO. An Avrami index of 2 can be a result of the instantaneous nucleation of axialitic crystals (i.e., two-dimensional aggregates of lamellar crystals), while n = 1 could be a result of the instantaneous growth of needle-like crystals. The AFM results (see Figure 4) show some morphological changes that could correspond to the change in the Avrami index. Furthermore, k1/n is a rate crystallization constant whose values provide information on the overall crystallization rate obtained by the Avrami model which correlate with the obtained experimental values.

Figure 4

Figure 4. (A) AFM-height images of PFO crystallized at Ta = 80 °C from an ISO state. (B) AFM-height images of PFO crystallized Ta = 80 °C from a NEM state. (C) Height histograms obtained from A and B AFM data. Height distributions in (C) are fitted to Gaussian curves.

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Finally, as a proxy for the final degree of crystallinity reached in the samples, the product between the melting enthalpy for the longest crystallization time and the sample mass (m) was analyzed, where the sample mass was constant (but unknown) in the whole study (Figure 3C). The results indicate that samples crystallized from an ISO state end up being more crystalline than those crystallized from a NEM state, especially for the lowest Ta analyzed. This, again, agrees with our interpretation that chain segment diffusion to the crystal growth front is more impeded in the NEM state during the secondary crystallization process.

Interplay between the Crystallization Kinetics and the Morphology and the Optical Response (AFM and Photoluminescence)

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Having established that preexisting molecular order significantly influences the crystallization kinetics of polymers, we analyzed whether the distinct kinetics found result in structural/morphological differences. Thus, samples crystallized both from the ISO state and the NEM state─thermally treated employing thermal protocols developed for kinetic studies with crystallization times of 10 h─were inspected by AFM (height images).
Tellingly, sample surfaces exhibit markedly different morphology/surface topography. The AFM images and their fast Fourier transform (shown inFigure 4S of the Supporting Information) revealed that PFO crystallized from the ISO state develops round-sized nanoscopic features (i.e., axialitic-like), whereas the sample crystallized from the NEM state seems to comprise more-elongated features (i.e., needle-like)
The height histograms for the sample crystallized from the ISO state exhibit a broad distribution, denoting regions with large height variations, that is, large roughness, whereas histograms for the PFO samples crystallized from the NEM state exhibit a narrow distribution of heights, corresponding to a more homogeneous surface (Figure 4C).
Motivated by the aforementioned findings that preexisting order alters the crystallization and the resulting solid-state morphology, we explored whether these changes have in turn an impact on the optoelectronic properties of the semiconducting polymer, for example, its optical emission properties (photoluminescence).
Figure 5 compares the average photoluminescence (PL) spectrum excited at 355 nm for the two samples. The two spectra generally show the same shape: the main 0–0 PL band followed by the first two phonon replicas. The most significant differences are in the relative intensity of the 00 and 01 transitions, with the ratio being smaller for the liquid-crystalline sample and a small blue shift of the PL peaks of the liquid-crystalline sample with respect to the isotropic one. Both of these features suggest a larger fraction of PFO chain segments with planar conformations and hence a larger degree of energetic order for the sample processed from the ISO state. This is most likely associated with a higher degree of crystallinity (1) in this sample as polymers tend to crystallize in lamellar crystals with polymer chains that adopt extended conformations that, in the case of rigid backbone polymers such as PFO, frequently imply planar conformations.

Figure 5

Figure 5. Photoluminescence spectra of crystallized FSC thin-film samples at Ta = 80 °C from an ISO state (blue) and from a NEM state (green).

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Conclusions

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In this work, we employ fast scanning chip calorimetry to study the crystallization kinetics from different states of a semiconducting semicrystalline material, PFO, opening new possibilities to investigate states of matter that would be otherwise inaccessible through conventional DSC techniques of other polymers in the field of organic electronics. We demonstrate that the preordered molecular domains in the NEM state facilitate the formation of effective nucleation sites for crystallization. However, they seem to hinder the diffusion of chain segments to the crystal growth front during the secondary crystallization stage, which slows down the crystal growth process. We argue that the different balance between nucleation and crystal growth between polymers crystallized from ordered and disordered liquids results in distinct solid-state morphologies and different degrees of crystallinity, which eventually impact the optical emission properties of materials. Therefore, our investigation clearly demonstrates a correlation between the preexisting molecular order in the crystallizable liquid, the crystallization kinetics, and the optoelectronic properties of solid semiconducting polymers. However, even more importantly, this work highlights that it is utterly important to conduct more fundamental investigations to gain full control over the optoelectronic properties of organic semiconductors.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.chemmater.2c02917.

  • PLOM experiments to determine the microscopic morphology of the material as a function of temperature; melting behavior of isothermal crystallized sample monitored by FSC at different Tas from both the ISO state and NEM state; and isothermal crystallization kinetics results from WAXS experiments and FFT analysis of AFM experiments (PDF)

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Author Information

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  • Corresponding Authors
    • Alejandro J. Müller - POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry, and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián20018, Spain;  IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5, Bilbao48009, Spain;  Orcidhttps://orcid.org/0000-0001-7009-7715;  Email: [email protected]
    • Jaime Martín - POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry, and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián20018, Spain;  IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5, Bilbao48009, Spain;  Universidade da Coruña, Campus Industrial de Ferrol, CITENI, Esteiro, Ferrol15403, Spain;  Orcidhttps://orcid.org/0000-0002-9669-7273;  Email: [email protected]
  • Authors
    • Valentina Pirela - POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry, and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián20018, Spain
    • Mariano Campoy-Quiles - Institute of Materials Science of Barcelona, ICMAB-CSIC, Campus UAB, Bellaterra08193, Spain;  Orcidhttps://orcid.org/0000-0002-8911-640X
  • Author Contributions

    The manuscript was written through the contributions of all authors. All authors have given approval to the final version of the manuscript.

  • Funding

    We acknowledge the support of the Basque Government through grant IT1503-22.J.M. We thank MICINN /FEDER for the Ramón y Cajal contract and the grant ref. PGC2018-094620 A-I00. The Xunta de Galicia is also acknowledged for the grant Proyectos de Consolidación ref. ED431F 2021/009

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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We are grateful to the De Mello group for providing the PFO material used in this work.

References

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This article references 38 other publications.

  1. 1
    Ariu, M.; Lidzey, D. G.; Lavrentiev, M.; Bradley, D. D. C.; Jandke, M.; Strohriegl, P. Study of the Different Structural Phases of the Polymer Poly(9,9′-Dioctyl Fluorene) Using Raman Spectroscopy. Synth. Met. 2001, 116, 217– 221,  DOI: 10.1016/s0379-6779(00)00456-2
    Google Scholar
    1
    A study of the different structural phases of the polymer poly(9,9'-dioctylfluorene) using Raman spectroscopy
    Ariu, M.; Lidzey, D. G.; Lavrentiev, M.; Bradley, D. D. C.; Jandke, M.; Strohriegl, P.
    Synthetic Metals (2001), 116 (1-3), 217-221CODEN: SYMEDZ; ISSN:0379-6779. (Elsevier Science S.A.)
    The polymer poly(9,9-dioctylfluorene) (F8) can be easily driven between a no. of different structural phases by different thermal or solvent treatments. The phases which the authors have identified include (i) as-spin-coated, (ii) semi-cryst., (iii) glassy, (iv) with an extended intrachain conformation. At. force microscopy was used to investigate the surface structures assocd. with the different phases of the polymer and different solvents used to cast the film. Raman spectroscopy was performed on these samples to understand how the polymer conformation changes with the phases. Variations in the relative intensity of the peaks and shifts in energy are obsd. The authors have compared the F8 spectrum with a trimer of fluorene with Bu side chains and acrylate/hydroxy end-groups attached to the fluorene main chain via hexyl spacers. They identify a very small frequency dispersion in the vibrational modes connected to an increase of the conjugation length. Therefore, the assignment of the vibrational modes of the trimer is very important for understanding the F8 spectrum.
  2. 2
    Jimison, L. H.; Toney, M. F.; McCulloch, I.; Heeney, M.; Salleo, A. Charge-Transport Anisotropy Due to Grain Boundaries in Directionally Crystallized Thin Films of Regioregular Poly(3-Hexylthiophene). Adv. Mater. 2009, 21, 1568– 1572,  DOI: 10.1002/adma.200802722
    Google Scholar
    2
    Charge-Transport Anisotropy Due to Grain Boundaries in Directionally Crystallized Thin Films of Regioregular Poly(3-hexylthiophene)
    Jimison, Leslie H.; Toney, Michael F.; McCulloch, Iain; Heeney, Martin; Salleo, Alberto
    Advanced Materials (Weinheim, Germany) (2009), 21 (16), 1568-1572CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A directional crystn. technique was used to produce poly(3-hexylthiophene) (P3HT) films that are highly anisotropic in plane, to study the charge-transport properties of grain boundaries between different orientations of crystallites. Boundaries along the fiber provide a small barrier to charge transport when compared to fiber-to-fiber grain boundaries. In these in-line grain boundaries, relatively straight polymer mols. provide an easy intergranular charge-transport path. Fiber-to-fiber grain boundaries act as large transport barriers, because intergranular chains cannot exist without sharp bends or twists, thus decreasing elec. connectivity. The data help to solidify the hypothesis that in low-angle grain boundaries transport is easier only in the direction parallel to the polymer backbone, due to bridging mols. Optimization of the microstructure in electronic devices should therefore not focus solely on the elimination of grain boundaries, but also include efforts to control grain-boundary placement and relative grain orientation.
  3. 3
    Yang, H.; Shin, T. J.; Yang, L.; Cho, K.; Ryu, C. Y.; Bao, Z. Effect of Mesoscale Crystalline Structure on the Field-Effect Mobility of Regioregular Poly(3-Hexyl Thiophene) in Thin-Film Transistors. Adv. Funct. Mater. 2005, 15, 671– 676,  DOI: 10.1002/adfm.200400297
    Google Scholar
    3
    Effect of mesoscale crystalline structure on the field-effect mobility of regioregular poly(3-hexyl thiophene) in thin-film transistors
    Yang, Hoichang; Shin, Tae Joo; Yang, Lin; Cho, Kilwon; Ryu, Chang Y.; Bao, Zhenan
    Advanced Functional Materials (2005), 15 (4), 671-676CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Regioregular poly(3-hexylthiophene) (RR P3HT) is drop-cast to fabricate field-effect transistor (FET) devices from different solvents with different b.ps. and solubilities for RR P3HT, such as methylene chloride, toluene, THF, and chloroform. A Petri dish is used to cover the soln., and it takes less than 30 min for the solvents to evap. at room temp. The mesoscale cryst. morphol. of RR P3HT thin films can be manipulated from well-dispersed nanofibrils to well-developed spherulites by changing soln. processing conditions. The morphol. correlation with the charge-carrier mobility in RR P3HT thin-film transistor (TFT) devices is investigated. The TFT devices show charge-carrier mobilities in the range of 10-4-10-2 cm2V-1s-1 depending on the solvent used, although grazing-incidence X-ray diffraction (GIXD) reveals that all films develop the same π-π-stacking orientation, where the <100>-axis is normal to the polymer films. By combining results from at. force microscopy (AFM) and GIXD, it is found that the morphol. connectivity of cryst. nanofibrils and the <100>-axis orientation distribution of the π-π-stacking plane with respect to the film normal play important roles on the charge-carrier mobility of RR P3HT for TFT applications.
  4. 4
    Noriega, R.; Rivnay, J.; Vandewal, K.; Koch, F. P. V.; Stingelin, N.; Smith, P.; Toney, M. F.; Salleo, A. A General Relationship between Disorder, Aggregation and Charge Transport in Conjugated Polymers. Nat. Mater. 2013, 12, 1038– 1044,  DOI: 10.1038/nmat3722
    Google Scholar
    4
    A general relationship between disorder, aggregation and charge transport in conjugated polymers
    Noriega, Rodrigo; Rivnay, Jonathan; Vandewal, Koen; Koch, Felix P. V.; Stingelin, Natalie; Smith, Paul; Toney, Michael F.; Salleo, Alberto
    Nature Materials (2013), 12 (11), 1038-1044CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
    Conjugated polymer chains have many degrees of conformational freedom and interact weakly with each other, resulting in complex microstructures in the solid state. Understanding charge transport in such systems, which have amorphous and ordered phases exhibiting varying degrees of order, has proved difficult owing to the contribution of electronic processes at various length scales. The growing technol. appeal of these semiconductors makes such fundamental knowledge extremely important for materials and process design. We propose a unified model of how charge carriers travel in conjugated polymer films. We show that in high-mol.-wt. semiconducting polymers the limiting charge transport step is trapping caused by lattice disorder, and that short-range intermol. aggregation is sufficient for efficient long-range charge transport. This generalization explains the seemingly contradicting high performance of recently reported, poorly ordered polymers and suggests mol. design strategies to further improve the performance of future generations of org. electronic materials.
  5. 5
    Yu, L.; Davidson, E.; Sharma, A.; Andersson, M. R.; Segalman, R.; Müller, C. Isothermal Crystallization Kinetics and Time-Temperature-Transformation of the Conjugated Polymer: Poly(3-(2′-Ethyl)Hexylthiophene). Chem. Mater. 2017, 29, 5654– 5662,  DOI: 10.1021/acs.chemmater.7b01393
    Google Scholar
    5
    Isothermal Crystallization Kinetics and Time-Temperature-Transformation of the Conjugated Polymer: Poly(3-(2'-ethyl)hexylthiophene)
    Yu, Liyang; Davidson, Emily; Sharma, Anirudh; Andersson, Mats R.; Segalman, Rachel; Muller, Christian
    Chemistry of Materials (2017), 29 (13), 5654-5662CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    Thermal annealing strongly impacts the nano- and microstructure of conjugated polymers. Despite the fundamental importance for the resulting opto-electronic behavior of this class of materials, the underlying crystn. processes have not received the same attention that is encountered in other disciplines of materials science. The question arises whether classical treatment of nucleation and growth phenomena is truly applicable to conjugated polymers. Here, the isothermal crystn. behavior of the conjugated polymer poly(3-(2'-ethyl)hexylthiophene) (P3EHT) is monitored with differential scanning calorimetry (DSC). Avrami anal. reveals growth- and nucleation limited temp. regimes that are sepd. by the max. rate of crystn. The mol. wt. of the polymer is found to strongly influence the abs. rate of crystn. at the same degree of undercooling relative to the melting temp. A combination of optical microscopy and grazing-incidence wide-angle X-ray scattering (GIWAXS) confirms that the resulting nano- and microstructure strongly correlate with the selected isothermal annealing temp. Hence, this work establishes that classical nucleation and growth theory can be applied to describe the solidification behavior of the semi-cryst. conjugated polymer P3EHT.
  6. 6
    Duong, D. T.; Ho, V.; Shang, Z.; Mollinger, S.; Mannsfeld, S. C. B.; Dacuña, J.; Toney, M. F.; Segalman, R.; Salleo, A. Mechanism of Crystallization and Implications for Charge Transport in Poly(3-Ethylhexylthiophene) Thin Films. Adv. Funct. Mater. 2014, 24, 4515– 4521,  DOI: 10.1002/adfm.201304247
    Google Scholar
    6
    Mechanism of Crystallization and Implications for Charge Transport in Poly(3-ethylhexylthiophene) Thin Films
    Duong, Duc T.; Ho, Victor; Shang, Zhengrong; Mollinger, Sonya; Mannsfeld, Stefan C. B.; Dacuna, Javier; Toney, Michael F.; Segalman, Rachel; Salleo, Alberto
    Advanced Functional Materials (2014), 24 (28), 4515-4521CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
    In this work, crystn. kinetics and aggregate growth of poly(3-ethylhexylthiophene) (P3EHT) thin films are studied as a function of film thickness. X-ray diffraction and optical absorption show that individual aggregates and crystallites grow anisotropically and mostly along only two packing directions: the alkyl stacking and the polymer chain backbone direction. Further, it is also detd. that crystn. kinetics is limited by the reorganization of polymer chains and depends strongly on the film thickness and av. mol. wt. Time-dependent, field-effect hole mobilities in thin films reveal a percolation threshold for both low and high mol. wt. P3EHT. Structural anal. reveals that charge percolation requires bridged aggregates sepd. by a distance of ≈2-3 nm, which is on the order of the polymer persistence length. These results thus highlight the importance of tie mols. and inter-aggregate distance in supporting charge percolation in semiconducting polymer thin films. The study as a whole also demonstrates that P3EHT is an ideal model system for polythiophenes and should prove to be useful for future investigations into crystn. kinetics.
  7. 7
    Zhao, Y.; Yuan, G.; Roche, P.; Leclerc, M. A Calorimetric Study of the Phase Transitions in Poly(3-Hexylthiophene). Polymer 1995, 36, 2211– 2214,  DOI: 10.1016/0032-3861(95)95298-f
    Google Scholar
    7
    A calorimetric study of the phase transitions in poly(3-hexylthiophene)
    Zhao, Yue; Yuan, Guoxiong; Roche, Philippe; Leclerc, Mario
    Polymer (1995), 36 (11), 2211-14CODEN: POLMAG; ISSN:0032-3861. (Elsevier)
    Differential scanning calorimetry was utilized for investigating the isothermal crystn. of a poly(3-hexylthiophene) (P3HT) sample over a wide range of temps. We found two well sepd. crystal formation processes: a fast process, essentially completed before the sample reaches the isothermal conditions, which produces crystals having higher transition temps. (at around 178°C), and a slow process which leads to continuous growth of less stable crystals, the transition temps. of which are detd. by the crystn. temp., namely, about 32°C above. The slow crystn. process occurs at temps. as low as 40°C. This crystn. behavior supports the suggestion that a nematic state exists in the melt of P3HT.
  8. 8
    Pal, S.; Nandi, A. K. Cocrystallization Mechanism of Poly(3-Hexyl Thiophenes) with Different Amount of Chain Regioregularity. J. Appl. Polym. Sci. 2006, 101, 3811– 3820,  DOI: 10.1002/app.24067
    Google Scholar
    8
    Cocrystallization mechanism of poly(3-hexyl thiophenes) with different amount of chain regioregularity
    Pal, Susmita; Nandi, Arun K.
    Journal of Applied Polymer Science (2006), 101 (6), 3811-3820CODEN: JAPNAB; ISSN:0021-8995. (John Wiley & Sons, Inc.)
    The overall crystn. rates of poly(3-hexyl thiophene) (P3HT) cocrystals with different amt. of regioregularity of the components are measured using differential scanning calorimetry (DSC). Two pairs of cocrystals with varying compns. of the component polymers (viz P3HT(R) (regioregularity 92 mol%)/P3HT-2 (regioregularity 82 mol%), and P3HT-2/P3HT-1 (regioregularity 75 mol%)) are used. The crystn. rate at the same isothermal crystn. temp. (Tc) decreases with increasing regioregularity. The low Avrami exponent values (0.15-1.0) in all the samples suggest the presence of rigid amorphous portion, which cannot diffuse out quickly from the crystal growth front (soft impingement). Anal. of crystn. rate using Laurintzen-Hoffman (L-H) growth rate theory indicates Regime I to Regime II transition in all the samples. The product of lateral and end surface energy values (σσe) increases gradually with increasing regioirregularity in the blend. Anal. of σ values indicates chain extension of the components in the melt of the blend and the entropy of activation (ΔSI-II) of the cocrystals are higher than those of the components. The entropy of cocrystn. (ΔSc) values are 1-2.4 e.u for P3HT(R)/P3HT-2 system and 0.5-1 e.u for P3HT-2/P3HT-1 system.
  9. 9
    Yang, G. Z.; Chen, X.; Wang, W.; Wang, M.; Liu, T.; Li, C. Z. Nonisothermal Crystallization and Melting Behavior of a Luminescent Conjugated Polymer, Poly(9,9-Dihexylfluorene-Alt-Co-2,5-Didecyloxy-1,4- Phenylene). J. Polym. Sci. Part B Polym. Phys. 2007, 45, 976– 987,  DOI: 10.1002/polb.21110
    Google Scholar
    9
    Nonisothermal crystallization and melting behavior of a luminescent conjugated polymer, poly(9,9-dihexylfluorene-alt-co-2,5-didecyloxy-1,4-phenylene)
    Yang, Gui-Zhong; Chen, Xiaolei; Wang, Weizhi; Wang, Min; Liu, Tianxi; Li, Chun-Zhong
    Journal of Polymer Science, Part B: Polymer Physics (2007), 45 (8), 976-987CODEN: JPBPEM; ISSN:0887-6266. (John Wiley & Sons, Inc.)
    The nonisothermal crystn. kinetics of a luminescent conjugated polymer, poly(9,9-dihexylfluorene-alt-co-2,5-didecyloxy-1,4-phenylene) (PF6OC10) with three different mol. wts. was studied by differential scanning calorimetry under different cooling rates from the melt. With increasing mol. wt. of PF6OC10, the temp. range of crystn. peak steadily became narrower and shifted to higher temp. region and the crystn. rate increased. The Ozawa method failed to describe the nonisothermal crystn. behavior of PF6OC10. Although the Avrami method did not effectively describe the nonisothermal crystn. kinetics of PF6OC10 for overall process, it was valid for describing the early stage of crystn. with an Avrami exponent n of about 3. The combined method, proposed by the authors was able to satisfactorily describe the nonisothermal crystn. behavior of PF6OC10. The crystn. activation energy detd. by Kissinger, Takhor, and Augis-Bennett models were comparable. The melting temp. of PF6OC10 increased with increasing mol. wt. For a low-mol.-wt. sample, PF6OC10 showed double melting phenomenon. The interval between the two melting peaks decreased with increasing mol. wt., and only one melting peak was obsd. for the high-mol.-wt. sample.
  10. 10
    Chen, X. L.; Huang, H. L.; Shi, J. G.; Liu, Y. L.; Wang, L. M. Isothermal Crystallization Kinetics and Melting Behavior of a Luminescent Conjugated Polymer, Poly(9,9-Dihexylfluorene-Alt-2,5-Didodecyloxybenzene). J. Macromol. Sci. Part B Phys. 2012, 51, 1049– 1056,  DOI: 10.1080/00222348.2011.625883
    Google Scholar
    10
    Isothermal Crystallization Kinetics and Melting Behavior of a Luminescent Conjugated Polymer, Poly(9,9-Dihexylfluorene-Alt-2,5-Didodecyloxybenzene)
    Chen, Xiao-Lei; Huang, Hong-Liang; Shi, Jian-Gao; Liu, Yong-Li; Wang, Lu-Min
    Journal of Macromolecular Science, Part B: Physics (2012), 51 (6), 1049-1056CODEN: JMAPBR; ISSN:0022-2348. (Taylor & Francis, Inc.)
    A study of the isothermal crystn. behaviors of poly(9,9-dihexylfluorene-alt-2,5-didodecyloxybenzene) (PF6OC12) was carried out using differential scanning calorimetry (DSC). The crystn. kinetics under isothermal conditions could be described by the Avrami equation. The Avrami exponent n ranges from 3.43 to 3.71 for PF6OC12 at crystn. temps. between 100.0°C and 90.0°C, indicating a three-dimensional spherical crystal growth with homogeneous nucleation in the primary crystn. stage for the isothermal melt crystn. process. In the DSC scan, after the isothermal crystn., multiple melting behavior was found. The multiple endotherms could be attributed to melting of recrystd. materials produced originally during different crystn. processes. According to the Arrhenius equation, the activation energy was detd. to be 211.29 kJmol-1 for the isothermal melt crystn. of PF6OC12.
  11. 11
    Chen, S. H.; Wu, Y. H.; Su, C. H.; Jeng, U.; Hsieh, C. C.; Su, A. C.; Chen, S. A. Cold Crystallization of Poly(9,9-Di-n-Octyl-2,7-Fluorene). Macromolecules 2007, 40, 5353– 5359,  DOI: 10.1021/ma070237g
    Google Scholar
    11
    Cold Crystallization of Poly(9,9-di-n-octyl-2,7-fluorene)
    Chen, S. H.; Wu, Y. H.; Su, C. H.; Jeng, U.; Hsieh, C. C.; Su, A. C.; Chen, S. A.
    Macromolecules (Washington, DC, United States) (2007), 40 (15), 5353-5359CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    We have previously demonstrated that soln.-cast films of conjugated polymers with grafted alkyl side chains comprise clearly identifiable domains ca. 10 nm in size upon solvent evapn. Here we show that these nanodomains indeed serve as basic units for morphol. development in poly(9,9-di-n-octyl-2,7-fluorene) (PFO) films during cold crystn. Results of our microscopic and diffraction observations indicate that the cold crystn. process involves intradomain nucleation and growth, followed by nanodomain alignment and coalescence into fibrils in the sub-micrometer length scale via thermally activated adjustment of nanodomain orientation. An analogy with oriented aggregation (or oriented attachment-coalescence) behavior of nanocrystals of metal oxides is drawn; the relevance to recently proposed models of polymer crystn. via primary nucleation induced at the growth front is addressed.
  12. 12
    Yang, G. Z.; Chen, X.; Xu, Y.; Li, C. Z.; Wu, P.; Liu, T. Nonisothermal Crystallization Behavior of a Luminescent Conjugated Polymer, Poly(9,9-Dihexylfluorene-Alt-2,5-Didodecyloxybenzene). Polym. Int. 2007, 56, 245– 251,  DOI: 10.1002/pi.2147
    Google Scholar
    12
    Nonisothermal crystallization behavior of a luminescent conjugated polymer, poly(9,9-dihexylfluorene-alt-2,5-didodecyloxybenzene)
    Yang, Gui-Zhong; Chen, Xiaolei; Xu, Yan; Li, Chun-Zhong; Wu, Peiyi; Liu, Tianxi
    Polymer International (2007), 56 (2), 245-251CODEN: PLYIEI; ISSN:0959-8103. (John Wiley & Sons Ltd.)
    The nonisothermal crystn. kinetics of poly(9,9-dihexylfluorene-alt-2,5-didodecyloxybenzene) (PF6OC12) from the melt were investigated using differential scanning calorimetry under different cooling rates. Several anal. methods were used to describe the nonisothermal crystn. behavior of PF6OC12. It was found that the modified Avrami method by Jeziorny was only valid for describing the early stage of crystn. but was not able to describe the later stage of PF6OC12 crystn. Also, the Ozawa method failed to describe the nonisothermal crystn. behavior of PF6OC12. However, the method developed by combining the Avrami and Ozawa equations could successfully describe the nonisothermal crystn. kinetics of PF6OC12. According to the Kissinger method, the activation energy was detd. to be 114.9 kJ mol-1 for the nonisothermal melt crystn. of PF6OC12.
  13. 13
    Perevedentsev, A.; Stavrinou, P. N.; Bradley, D. D. C.; Smith, P. Solution-Crystallization and Related Phenomena in 9,9-Dialkyl-Fluorene Polymers. I. Crystalline Polymer-Solvent Compound Formation for Poly(9,9-Dioctylfluorene). J. Polym. Sci. Part B Polym. Phys. 2015, 53, 1481– 1491,  DOI: 10.1002/polb.23798
    Google Scholar
    13
    Solution-crystallization and related phenomena in 9,9-dialkyl-fluorene polymers. I. Crystalline polymer-solvent compound formation for poly(9,9-dioctylfluorene)
    Perevedentsev, Aleksandr; Stavrinou, Paul N.; Bradley, Donal D. C.; Smith, Paul
    Journal of Polymer Science, Part B: Polymer Physics (2015), 53 (21), 1481-1491CODEN: JPBPEM; ISSN:0887-6266. (John Wiley & Sons, Inc.)
    Polymer-solvent compd. formation, occurring via co-crystn. of polymer chains and selected small-mol. species, is demonstrated for the conjugated polymer poly(9,9-dioctylfluorene) (PFO) and a range of org. solvents. The resulting crystn. and gelation processes in PFO solns. are studied by differential scanning calorimetry, with X-ray diffraction providing addnl. information on the resulting microstructure. It is shown that PFO-solvent compds. comprise an ultra-regular mol.-level arrangement of the semiconducting polymer host and small-mol. solvent guest. Crystals form following adoption of the planar-zigzag β-phase chain conformation, which, due to its geometry, creates periodic cavities that accommodate the ordered inclusion of solvent mols. of matching vol. The findings are formalized in terms of nonequil. temp.-compn. phase diagrams. The potential applications of these compds. and the new functionalities that they might enable are also discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015.
  14. 14
    Bridges, C. R.; Ford, M. J.; Bazan, G. C.; Segalman, R. A. Molecular Considerations for Mesophase Interaction and Alignment of Lyotropic Liquid Crystalline Semiconducting Polymers. ACS Macro Lett. 2017, 6, 619– 624,  DOI: 10.1021/acsmacrolett.7b00273
    Google Scholar
    14
    Molecular Considerations for Mesophase Interaction and Alignment of Lyotropic Liquid Crystalline Semiconducting Polymers
    Bridges, Colin R.; Ford, Michael J.; Bazan, Guillermo C.; Segalman, Rachel A.
    ACS Macro Letters (2017), 6 (6), 619-624CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
    Intermol. interactions in conjugated polymers influence crystallinity, self-assembly, and packing motif, factors which in turn crucially impact charge transport properties such as carrier mobility in org. electronic devices. Correlated alignment of mol. and cryst. morphologies provides direct pathways for charge carriers to follow; however, the role of intermol. interactions in achieving this is unexplored. Herein, we synthesize a series of lyotropic liq. cryst. conjugated polymers with variable side-chain structure to lend distinct steric repulsion and van der Waals attractive forces to each mesophase. We use this to study the role of intermol. interactions on mesophase alignment. The strength of intermol. interaction for each mesophase is compared by measuring melting temp., π-stacking distance, and the Maier-Saupe interaction parameter. In general we find that side-chain structure can impact interaction strength by varying steric repulsion and backbone attractions and that the Maier-Saupe interaction parameters correlate with higher degrees of alignment after shearing, achieving a dichroic absorbance ratio of up to 2. This observation is used to develop equil. processing methods for fabricating macroscopically aligned polymer substrates used in transistors, improving mobility by a factor of 3 compared to spin-coated devices.
  15. 15
    Zhang, L.; Zhao, K.; Li, H.; Zhang, T.; Liu, D.; Han, Y. Liquid Crystal Ordering on Conjugated Polymers Film Morphology for High Performance. J. Polym. Sci. Part B Polym. Phys. 2019, 57, 1572– 1591,  DOI: 10.1002/polb.24885
    Google Scholar
    15
    Liquid Crystal Ordering on Conjugated Polymers Film Morphology for High Performance
    Zhang, Lu; Zhao, Kefeng; Li, Hongxiang; Zhang, Tao; Liu, Duo; Han, Yanchun
    Journal of Polymer Science, Part B: Polymer Physics (2019), 57 (23), 1572-1591CODEN: JPBPEM; ISSN:0887-6266. (John Wiley & Sons, Inc.)
    A review. The electronic performance of conjugated polymers depends on the microstructure of the polymer films. A percolated network morphol. with high crystallinity, ordered intermol. packing and long-range order is beneficial for charge transport. In recent reports, some conjugated polymers have been shown to exhibit liq. crystallinity. The appearance of liq. cryst. ordering provides a new soln. to solve the difficulties in microstructure manipulation. In this review, we summarize how liq. crystallinity can assist mol. arrangement and guide long-range orientation during film processing, leading to high charge mobility. We expect that this article could draw more attention to the liq. crystallinity of conjugated polymers.
  16. 16
    McCulloch, I.; Heeney, M.; Bailey, C.; Genevicius, K.; MacDonald, I.; Shkunov, M.; Sparrowe, D.; Tierney, S.; Wagner, R.; Zhang, W.; Chabinyc, M. L.; Kline, R. J.; McGehee, M. D.; Toney, M. F. Liquid-Crystalline Semiconducting Polymers with High Charge-Carrier Mobility. Nat. Mater. 2006, 5, 328– 333,  DOI: 10.1038/nmat1612
    Google Scholar
    16
    Liquid-crystalline semiconducting polymers with high charge-carrier mobility
    McCulloch, Iain; Heeney, Martin; Bailey, Clare; Genevicius, Kristijonas; MacDonald, Iain; Shkunov, Maxim; Sparrowe, David; Tierney, Steve; Wagner, Robert; Zhang, Weimin; Chabinyc, Michael L.; Kline, R. Joseph; McGehee, Michael D.; Toney, Michael F.
    Nature Materials (2006), 5 (4), 328-333CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
    Org. semiconductors that can be fabricated by simple processing techniques and possess excellent elec. performance, are key requirements in the progress of org. electronics. Both high semiconductor charge-carrier mobility, optimized through understanding and control of the semiconductor microstructure, and stability of the semiconductor to ambient electrochem. oxidative processes are required. The authors report on new semiconducting liq.-cryst. thieno[3,2-b ]thiophene polymers, the enhancement in charge-carrier mobility achieved through highly organized morphol. from processing in the mesophase, and the effects of exposure to both ambient and low-humidity air on the performance of transistor devices. Relatively large cryst. domain sizes on the length scale of lithog. accessible channel lengths (∼200 nm) were exhibited in thin films, thus offering the potential for fabrication of single-crystal polymer transistors. Good transistor stability under static storage and operation in a low-humidity air environment was demonstrated, with charge-carrier field-effect mobilities of 0.2-0.6 cm2 V-1 s-1 achieved under nitrogen.
  17. 17
    Bridges, C. R.; Ford, M. J.; Popere, B. C.; Bazan, G. C.; Segalman, R. A. Formation and Structure of Lyotropic Liquid Crystalline Mesophases in Donor-Acceptor Semiconducting Polymers. Macromolecules 2016, 49, 7220– 7229,  DOI: 10.1021/acs.macromol.6b01650
    Google Scholar
    17
    Formation and Structure of Lyotropic Liquid Crystalline Mesophases in Donor-Acceptor Semiconducting Polymers
    Bridges, Colin R.; Ford, Michael J.; Popere, Bhooshan C.; Bazan, Guillermo C.; Segalman, Rachel A.
    Macromolecules (Washington, DC, United States) (2016), 49 (19), 7220-7229CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Controlling crystallinity and mol. packing at nano- and macroscopic length scales in conjugated polymer thin films is vital for improving the performance of polymer-based electronic devices. Herein, the inherent amphiphilicity of rigid donor-acceptor copolymers used in high performance polymer electronics is leveraged to allow the formation of highly ordered lyotropic mesophases. By increasing the length and branching of solubilizing chains on cyclopentadithiophene-alt-thiadiazolopyridine-based alternating copolymers, amphiphilicity can be increased, and lyotropic liq. cryst. mesophases are obsd. in selective solvents. These lyotropic mesophases consist of chain extended polymers exhibiting close, ordered π-stacking. This is evidenced by birefringent solns. and red-shifted absorbance spectra displaying pronounced excitonic coupling. Crystallinity developed in soln. can be transferred to the solid state, and thin films of donor-acceptor copolymers cast from lyotropic solns. exhibit improved cryst. order in both the alkyl and π-stacking directions. Because of this improved crystallinity, transistors with active layers cast from lyotropic solns. exhibit a significant improvement in carrier mobility compared to those cast from isotropic soln., reaching a max. value of 0.61 cm2 V-1 s-1. This approach of rational side chain design bridges the gap from soln. structure to solid state structure and is a promising and general approach to allow the expression of lyotropic mesophases in rigid conjugated polymers.
  18. 18
    Marina, S.; Gutierrez-Fernandez, E.; Gutierrez, J.; Gobbi, M.; Ramos, N.; Solano, E.; Rech, J.; You, W.; Hueso, L. E.; Tercjak, A.; Ade, H.; Martin, J. Semi-Paracrystallinity in Semi-Conducting Polymers. Mater. Horizons 2022, 9, 1196– 1206,  DOI: 10.1039/d1mh01349a
    Google Scholar
    18
    Semi-paracrystallinity in semi-conducting polymers
    Marina, Sara; Gutierrez-Fernandez, Edgar; Gutierrez, Junkal; Gobbi, Marco; Ramos, Nicolas; Solano, Eduardo; Rech, Jeromy; You, Wei; Hueso, Luis; Tercjak, Agnieszka; Ade, Harald; Martin, Jaime
    Materials Horizons (2022), 9 (4), 1196-1206CODEN: MHAOBM; ISSN:2051-6355. (Royal Society of Chemistry)
    Precise detn. of structural organization of semi-conducting polymers is of paramount importance for the further development of these materials in org. electronic technologies. Yet, prior characterization of some of the best-performing materials for transistor and photovoltaic applications, which are based on polymers with rigid backbones, often resulted in conundrums in which X-ray scattering and microscopy yielded seemingly contradicting results. Here we solve the paradox by introducing a new structural model, i.e., semi-paracryst. organization. The model establishes that the microstructure of these materials relies on a dense array of small paracryst. domains embedded in a more disordered matrix. Thus, the overall structural order relies on two parameters: the novel concept of degree of paracrystallinity (i.e., paracryst. vol./mass fraction, introduced here for the first time) and the lattice distortion parameter of paracryst. domains (g-parameter from X-ray scattering). Structural parameters of the model are correlated with long-range charge carrier transport, revealing that charge transport in semi-paracryst. materials is particularly sensitive to the interconnection of paracryst. domains.
  19. 19
    Liu, X.; Huettner, S.; Rong, Z.; Sommer, M.; Friend, R. H. Solvent Additive Control of Morphology and Crystallization in Semiconducting Polymer Blends. Adv. Mater. 2012, 24, 669– 674,  DOI: 10.1002/adma.201103097
    Google Scholar
    19
    Solvent Additive Control of Morphology and Crystallization in Semiconducting Polymer Blends
    Liu, Xueliang; Huettner, Sven; Rong, Zhuxia; Sommer, Michael; Friend, Richard H.
    Advanced Materials (Weinheim, Germany) (2012), 24 (5), 669-674CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    BrAni (4-bromoanisole) is an effective and versatile solvent additive for promoting P3HT crystn. during processing of different P3HT-contg. blends is demonstrated. The mechanism is attributed to its lower volatility than the principal solvent, and its selective soly. as confirmed with studies of absorption spectra and solvent-vapor swelling isotherms. Furthermore, P3HT crystn. induced during film formation can reduce the dependence of morphol. on the often different natural demixing behavior of various P3HT blends, there by allowing pure, ordered and interpenetrating domains close to the ideal size to be formed for a no. of different acceptor choices. This improved morphol. in turn led to enhanced OPV performance than using conventional thermal annealing alone, particularly for polymer-polymer systems. Finally, we draw attention to the defining role that the design and development of new conjugated semiconducting polymers has made in this field.
  20. 20
    Liu, Y.; Zhao, J.; Li, Z.; Mu, C.; Ma, W.; Hu, H.; Jiang, K.; Lin, H.; Ade, H.; Yan, H. Aggregation and Morphology Control Enables Multiple Cases of High-Efficiency Polymer Solar Cells. Nat. Commun. 2014, 5, 1– 8,  DOI: 10.1038/ncomms6293
    Google Scholar
    There is no corresponding record for this reference.
  21. 21
    Luzio, A.; Nübling, F.; Martin, J.; Fazzi, D.; Selter, P.; Gann, E.; McNeill, C. R.; Brinkmann, M.; Hansen, M. R.; Stingelin, N.; Sommer, M.; Caironi, M. Microstructural Control Suppresses Thermal Activation of Electron Transport at Room Temperature in Polymer Transistors. Nat. Commun. 2019, 10, 3365,  DOI: 10.1038/s41467-019-11125-9
    Google Scholar
    21
    Microstructural control suppresses thermal activation of electron transport at room temperature in polymer transistors
    Luzio Alessandro; Caironi Mario; Nubling Fritz; Sommer Michael; Martin Jaime; Martin Jaime; Fazzi Daniele; Selter Philipp; Hansen Michael Ryan; Gann Eliot; McNeill Christopher R; Gann Eliot; Gann Eliot; Brinkmann Martin; Stingelin Natalie
    Nature communications (2019), 10 (1), 3365 ISSN:.
    Recent demonstrations of inverted thermal activation of charge mobility in polymer field-effect transistors have excited the interest in transport regimes not limited by thermal barriers. However, rationalization of the limiting factors to access such regimes is still lacking. An improved understanding in this area is critical for development of new materials, establishing processing guidelines, and broadening of the range of applications. Here we show that precise processing of a diketopyrrolopyrrole-tetrafluorobenzene-based electron transporting copolymer results in single crystal-like and voltage-independent mobility with vanishing activation energy above 280 K. Key factors are uniaxial chain alignment and thermal annealing at temperatures within the melting endotherm of films. Experimental and computational evidences converge toward a picture of electrons being delocalized within crystalline domains of increased size. Residual energy barriers introduced by disordered regions are bypassed in the direction of molecular alignment by a more efficient interconnection of the ordered domains following the annealing process.
  22. 22
    Padmaja, S.; Ajita, N.; Srinivasulu, M.; Girish, S. R.; Pisipati, V. G. K. M.; Potukuchi, D. M. Crystallization Kinetics in Liquid Crystals with Hexagonal Precursor Phases by Calorimetry. Zeitschrift fur Naturforsch. - Sect. A J. Phys. Sci. 2010, 65, 733– 744,  DOI: 10.1515/zna-2010-8-916
    Google Scholar
    There is no corresponding record for this reference.
  23. 23
    Carpaneto, L.; Marsano, E.; Valenti, B.; Zanardi, G. Crystallization and Melting Behaviour of a Semirigid Liquid-Crystalline Polyester. Polymer 1992, 33, 3865– 3872,  DOI: 10.1016/0032-3861(92)90374-6
    Google Scholar
    23
    Crystallization and melting behavior of a semirigid liquid-crystalline polyester
    Carpaneto, L.; Marsano, E.; Valenti, B.; Zanardi, G.
    Polymer (1992), 33 (18), 3865-72CODEN: POLMAG; ISSN:0032-3861.
    DSC was used to investigate the thermal behavior of a mesogenic polyester built up of a flexible spacer of 8 CH2 units and a rigid arom. ester triad. Nonisothermal crystns. at different cooling rates and isothermal crystns. at various temps. were carried out; the variations of the melting temps. and enthalpies as a function of the crystn. parameters were investigated. The melting profiles of the treated samples reveal 2 endotherms at temps. Tm1 and Tm2, which could not be interpreted as usually reported for conventional polymers. A new model of crystn. was proposed, taking into account that a certain registry of neighboring chains persists in the nematic state above Tm, and becomes poorer and poorer on increasing the temp. and time; this persistent registry can be regarded as potential nuclei of crystn., responsible for the high-temp. endotherm. Therefore, the presence of multiple endotherms in the melting profile of thermotropic polymers crystd. from the liq.-cryst. state appears to be a consequence of the annealing conditions in the nematic phase.
  24. 24
    Katerska, B.; Exner, G.; Perez, E.; Krasteva, M. N. Cooling Rate Effect on the Phase Transitions in a Polymer Liquid Crystal: DSC and Real-Time MAXS and WAXD Experiments. Eur. Polym. J. 2010, 46, 1623– 1632,  DOI: 10.1016/j.eurpolymj.2010.03.018
    Google Scholar
    24
    Cooling rate effect on the phase transitions in a polymer liquid crystal: DSC and real-time MAXS and WAXD experiments
    Katerska, Borislava; Exner, Ginka; Perez, Ernesto; Krasteva, Manya N.
    European Polymer Journal (2010), 46 (7), 1623-1632CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Ltd.)
    The importance of the cooling rate for the structural transformations in a main-chain poly(hexamethylene-4,4'-bibenzoate) was presented. Detailed anal. of the phase transitions, main structural parameters and their temp. changes was performed by differential scanning calorimetry, real-time middle-angle x-ray scattering and wide-angle x-ray diffraction methods. The thermodn. nature of the initial transformation into a smectic A phase was discussed. The material in the smectic state is supposed to be organized in smectic domains. The crystn. from the smectic phase depends strongly on the kinetics. The crystn. inside the smectic domains results into different final structures detd. by the cooling rate applied. At the highest cooling rates, only one cryst. form was obsd. Different possible modifications were discussed for the case: either a γ-polymorphic form or still some mesophase of high order, as a frozen metastable state. There is a possibility that the phase might be also identified as a condis crystal. At decreasing cooling rates, a new cryst. form, named α*, appears together with the first one. Lowering the cooling rate, the vol. fraction of the α*-polymorph gradually increases, at the expenses of the first form. The interesting feature of the new obsd. α*-polymorph is that it has some similarities with α- and δ-phases of the same material. Contrary to the previous observations, no γ ⇔α* transformation was obsd. neither during the course of single crystn. nor during the subsequent heating. A model describing the gradual transformation of the material during its temp. treatment was proposed.
  25. 25
    Androsch, R.; Soccio, M.; Lotti, N.; Cavallo, D.; Schick, C. Cold-Crystallization of Poly(Butylene 2,6-Naphthalate) Following Ostwald’s Rule of Stages. Thermochim. Acta 2018, 670, 71– 75,  DOI: 10.1016/j.tca.2018.10.015
    Google Scholar
    25
    Cold-crystallization of poly(butylene 2,6-naphthalate) following Ostwald's rule of stages
    Androsch, Rene; Soccio, Michelina; Lotti, Nadia; Cavallo, Dario; Schick, Christoph
    Thermochimica Acta (2018), 670 (), 71-75CODEN: THACAS; ISSN:0040-6031. (Elsevier B.V.)
    Melt-crystn. of poly (butylene 2,6-naphthalate) (PBN) at temps. lower than about 160 °C follows Ostwald's rule of stages, leading first to formation of a transient smectic liq. cryst. phase (LC) which then may convert in a second step into crystals, controlled by kinetics. In the present work, the PBN melt was cooled at different rates in a fast scanning chip calorimeter to below the glass transition temp., to obtain different structural states before anal. of the cold-crystn. behavior on heating. It was found that heating of fully amorphous PBN at 1000 K/s leads to a similar two-step crystn. process as on cooling the quiescent melt, with LC-formation occurring slightly above Tg and their transformation into crystals at their stability limit close to 200 °C. In-situ polarized-light optical microscopy provided information that the transition of the LC-phase into crystals on slow heating is not connected with a change of the micrometer-scale superstructure, as the recently found Schlieren texture remains unchanged.
  26. 26
    Ding, Q.; Soccio, M.; Lotti, N.; Cavallo, D.; Androsch, R. Melt Crystallization of Poly(Butylene 2,6-Naphthalate). Chinese J. Polym. 2020, 38, 311– 322,  DOI: 10.1007/s10118-020-2354-5
    Google Scholar
    26
    Melt Crystallization of Poly(butylene 2,6-naphthalate)
    Ding, Qian; Soccio, Michelina; Lotti, Nadia; Cavallo, Dario; Androsch, Rene
    Chinese Journal of Polymer Science (2020), 38 (4), 311-322CODEN: CJPSEG; ISSN:0256-7679. (Springer)
    A review. Poly(butylene 2,6-naphthalate) (PBN) is a crystallizable linear polyester contg. a rigid naphthalene unit and flexible methylene spacer in the chem. repeat unit. Polymeric materials made of PBN exhibit excellent anti-abrasion and low friction properties, superior chem. resistance, and outstanding gas barrier characteristics. Many of the properties rely on the presence of crystals and the formation of a semicryst. morphol. To develop specific crystal structures and morphologies during cooling the melt, precise information about the melt-crystn. process is required. This review article summarizes the current knowledge about the temp.-controlled crystal polymorphism of PBN. At rather low supercooling of the melt, with decreasing crystn. temp., β'- and α-crystals grow directly from the melt and organize in largely different spherulitic superstructures. Formation of α-crystals at high supercooling may also proceed via intermediate formation of a transient monotropic liq. cryst. structure, then yielding a non-spherulitic semicryst. morphol. Crystn. of PBN is rather fast since its suppression requires cooling the melt at a rate higher than 6000 K·s-1. For this reason, investigation of the two-step crystn. process at low temps. requires application of sophisticated exptl. tools. These include temp.-resolved X-ray scattering techniques using fast detectors and synchrotron-based X-rays and fast scanning chip calorimetry. Fast scanning chip calorimetry allows freezing the transient liq.-cryst. structure before its conversion into α-crystals, by fast cooling to below its glass transition temp. Subsequent anal. using polarized-light optical microscopy reveals its texture and X-ray scattering confirms the smectic arrangement of the mesogens. The combination of a large variety of exptl. techniques allows obtaining a complete picture about crystn. of PBN in the entire range of melt-supercoolings down to the glass transition, including quant. data about the crystn. kinetics, semicryst. morphologies at the micrometer length scale, as well as nanoscale X-ray structure information.
  27. 27
    Ding, Q.; Jehnichen, D.; Göbel, M.; Soccio, M.; Lotti, N.; Cavallo, D.; Androsch, R. Smectic Liquid Crystal Schlieren Texture in Rapidly Cooled Poly(Butylene Naphthalate). Eur. Polym. J. 2018, 101, 90– 95,  DOI: 10.1016/j.eurpolymj.2018.02.010
    Google Scholar
    27
    Smectic liquid crystal Schlieren texture in rapidly cooled poly(butylene naphthalate)
    Ding, Qian; Jehnichen, Dieter; Gobel, Michael; Soccio, Michelina; Lotti, Nadia; Cavallo, Dario; Androsch, Rene
    European Polymer Journal (2018), 101 (), 90-95CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Ltd.)
    The morphol. of partially cryst./ordered poly(butylene naphthalate) (PBN) forming on cooling the melt has been analyzed by polarized-light optical microscopy (POM) and microfocus-beam X-ray diffraction (XRD). Crystn. at rather low supercooling of the melt, at temps. higher than about 200°C, leads to slow and irregular spherulitic growth of β'-crystals, with spherulites not showing a distinct Maltese cross in POM. At temps. between approx. 200 and 160°C, the melt partially converts directly to α-crystals, and the obtained spherulitic superstructure reveals an increasing nuclei d. with decreasing crystn. temp. At even lower temp., a liq. cryst. (LC) phase develops. This mesophase may subsequently convert to α-crystals according to Ostwald's rule of stages. The transition of the LC-phase into α-crystals is suppressed at temps. lower than about 120°C or on cooling faster than about 200-500K/s. X-ray anal. of PBN liq. crystals formed at well-defined cooling conditions in a fast scanning chip calorimeter revealed smectic periodicity while there is simultaneously obsd. a distinct Schlieren texture in POM.
  28. 28
    Cavallo, D.; Mileva, D.; Portale, G.; Zhang, L.; Balzano, L.; Alfonso, G. C.; Androsch, R. Mesophase-Mediated Crystallization of Poly(Butylene-2,6- Naphthalate): An Example of Ostwald’s Rule of Stages. ACS Macro Lett. 2012, 1, 1051– 1055,  DOI: 10.1021/mz300349z
    Google Scholar
    28
    Mesophase-Mediated Crystallization of Poly(butylene-2,6-naphthalate): An Example of Ostwald's Rule of Stages
    Cavallo, Dario; Mileva, Daniela; Portale, Giuseppe; Zhang, Li; Balzano, Luigi; Alfonso, Giovanni C.; Androsch, Rene
    ACS Macro Letters (2012), 1 (8), 1051-1055CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
    The investigation of poly(butylene-2,6-naphthalate) crystn. by means of chip-calorimetry and ultrafast wide-angle X-ray diffraction (WAXD) revealed the existence of two possible mechanisms. The formation of the stable triclinic α-phase occurs directly from the undercooled melt at low cooling rates/high crystn. temp. At higher cooling rates a two-stage route is obsd.: crystn. was preceded by the formation of a mesomorphic phase from the isotropic melt. The monotropic behavior of poly(butylene-2,6-naphthalate), becoming apparent only under severe cooling conditions, obeys the well-known Ostwald's rule of stages.
  29. 29
    Martin, J.; Davidson, E. C.; Greco, C.; Xu, W.; Bannock, J. H.; Agirre, A.; de Mello, J.; Segalman, R. A.; Stingelin, N.; Daoulas, K. C. Temperature-Dependence of Persistence Length Affects Phenomenological Descriptions of Aligning Interactions in Nematic Semiconducting Polymers. Chem. Mater. 2018, 30, 748– 761,  DOI: 10.1021/acs.chemmater.7b04194
    Google Scholar
    29
    Temperature-Dependence of Persistence Length Affects Phenomenological Descriptions of Aligning Interactions in Nematic Semiconducting Polymers
    Martin, Jaime; Davidson, Emily C.; Greco, Cristina; Xu, Wenmin; Bannock, James H.; Agirre, Amaia; de Mello, John; Segalman, Rachel A.; Stingelin, Natalie; Daoulas, Kostas Ch.
    Chemistry of Materials (2018), 30 (3), 748-761CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    Electronic and optical properties of conjugated polymers are strongly affected by their solid-state microstructure. In nematic polymers, mesoscopic order and structure can be theor. understood using Maier-Saupe (MS) models, motivating us to apply them to conjugated macromol. systems and consider the problem of their material-specific parametrization. MS models represent polymers by worm-like chains (WLC) and can describe collective polymer alignment through anisotropic MS interactions. Their strength is controlled by a phenomenol. temp.-dependent parameter, υ(T). We undertake the challenging task of estg. material-specific υ(T), combining expts. and SCF theory (SCFT). Considering three different materials and a spectrum of mol. wts., we cover the cases of rod-like, semiflexible, and flexible conjugated polymers. The temp. of the isotropic-nematic transition, TIN, is identified via polarized optical microscopy and spectroscopy. The polymers are mapped on WLC with temp.-dependent persistence length. Fixed persistence lengths are also considered, reproducing situations addressed in earlier studies. We est. υ(T) by matching TIN in expts. and SCFT treatment of the MS model. An important conclusion is that accounting explicitly for changes of persistence length with temp. has significant qual. effects on υ(T). We moreover correlate our findings with earlier discussions on the thermodn. nature of phenomenol. MS interactions.
  30. 30
    Kawamura, T.; Misaki, M.; Koshiba, Y.; Horie, S.; Kinashi, K.; Ishida, K.; Ueda, Y. Crystalline Thin Films of β-Phase Poly(9,9-Dioctylfluorene). Thin Solid Films 2011, 519, 2247– 2250,  DOI: 10.1016/j.tsf.2010.10.048
    Google Scholar
    30
    Crystalline thin films of β-phase poly(9,9-dioctylfluorene)
    Kawamura, Takuji; Misaki, Masahiro; Koshiba, Yasuko; Horie, Satoshi; Kinashi, Kenji; Ishida, Kenji; Ueda, Yasukiyo
    Thin Solid Films (2011), 519 (7), 2247-2250CODEN: THSFAP; ISSN:0040-6090. (Elsevier B.V.)
    The detailed structure of cryst. β-phase poly(9,9-dioctylfluorene) (PFO) films was studied by polarized optical measurements, transmission electron microscopy, and grazing-incidence X-ray diffraction. Cryst. β-phase PFO thin films were fabricated by a friction transfer technique and subsequent vapor treatment. Compared to the α-phase, the lattice parameters of the β-phase crystals shrank along the a-axis (film thickness direction) and elongated along the b-axis (side-chain direction), but the period along the c-axis (main-chain direction) remained nearly equal. These changes in mol. packing were consistent with a planar conformational change from the α-phase to the β-phase of PFO.
  31. 31
    Elshaikh, M.; Marouf, A. A. S.; Modwi, A.; Ibnaouf, K. H. Influence of the Organic Solvents on the α and β Phases of a Conjugated Polymer (PFO). Dig. J. Nanomater. Biostructures 2019, 14, 1069– 1077
    Google Scholar
    There is no corresponding record for this reference.
  32. 32
    Wang, W.; Fenni, S. E.; Ma, Z.; Righetti, M. C.; Cangialosi, D.; Di Lorenzo, M. L.; Cavallo, D. Glass Transition and Aging of the Rigid Amorphous Fraction in Polymorphic Poly(Butene-1). Polymer 2021, 226, 1– 9,  DOI: 10.1016/j.polymer.2021.123830
    Google Scholar
    There is no corresponding record for this reference.
  33. 33
    Cangialosi, D.; Alegría, A.; Colmenero, J. Cooling Rate Dependent Glass Transition in Thin Polymer Films and in Bulk. In Fast Scanning Calorimetry , 2016, pp 403– 431.
    Google Scholar
    There is no corresponding record for this reference.
  34. 34
    Martín, J.; Stingelin, N.; Cangialosi, D. Direct Calorimetric Observation of the Rigid Amorphous Fraction in a Semiconducting Polymer. J. Phys. Chem. Lett. 2018, 9, 990– 995
    Google Scholar
    34
    Direct Calorimetric Observation of the Rigid Amorphous Fraction in a Semiconducting Polymer
    Martin, Jaime; Stingelin, Natalie; Cangialosi, Daniele
    Journal of Physical Chemistry Letters (2018), 9 (5), 990-995CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    The performance of polymeric semiconductors is profoundly affected by the thermodn. state of its cryst. and amorphous fractions and how they affect the optoelectronic properties. While intense research has been conducted on the cryst. features, fundamental understanding of the amorphous fraction(s) is still lacking. Here, we employ fast scanning calorimetry to provide insights on the glass transition of the archetypal conjugated polymer poly(3-hexylthiophene) (P3HT). According to the conceptual definition of the glass transition temp. (Tg), i.e., the temp. marking the crossover from the melt in metastable equil. to the nonequil. glass, an enthalpy relaxation should be obsd. by calorimetry when the glass is aged below Tg. Thus, we are able to identify the enthalpy relaxations of mobile and rigid amorphous fractions (MAF and RAF, resp.) of P3HT and to det. their resp. Tg. Our work moreover highlights that the RAF should be included in structural models when establishing structure/property interrelationships of polymer semiconductors.
  35. 35
    Lorenzo, A. T.; Arnal, M. L.; Albuerne, J.; Müller, A. J. DSC Isothermal Polymer Crystallization Kinetics Measurements and the Use of the Avrami Equation to Fit the Data: Guidelines to Avoid Common Problems. Polym. Test. 2007, 26, 222– 231,  DOI: 10.1016/j.polymertesting.2006.10.005
    Google Scholar
    35
    DSC isothermal polymer crystallization kinetics measurements and the use of the Avrami equation to fit the data: Guidelines to avoid common problems
    Lorenzo, Arnaldo T.; Arnal, Maria Luisa; Albuerne, Julio; Mueller, Alejandro J.
    Polymer Testing (2007), 26 (2), 222-231CODEN: POTEDZ; ISSN:0142-9418. (Elsevier B.V.)
    Guidelines were developed to adequately fit isothermal polymer crystn. kinetics data obtained by differential scanning calorimetry (DSC) using the Avrami equation. A methodol. on how the exptl. DSC data should be measured and later analyzed to minimize possible errors assocd. with data manipulation is provided by a thorough evaluation of: (i) detn. of the onset of crystn. or induction time, (ii) the establishment of the baseline and incomplete isothermal crystn. data, (iii) the effect of cooling rate from the melt to isothermal crystn. temp., and (iv) the conversion range used for fitting.
  36. 36
    Pérez-Camargo, R. A.; Liu, G. M.; Wang, D. J.; Müller, A. J. Experimental and Data Fitting Guidelines for the Determination of Polymer Crystallization Kinetics. Chinese J. Polym. Sci. 2022, 40, 658– 691
    Google Scholar
    36
    Experimental and Data Fitting Guidelines for the Determination of Polymer Crystallization Kinetics
    Perez-Camargo, Ricardo Arpad; Liu, Guo-Ming; Wang, Du-Jin; Muller, Alejandro J.
    Chinese Journal of Polymer Science (2022), 40 (6), 658-691CODEN: CJPSEG; ISSN:0256-7679. (Springer)
    A review. The crystn. kinetics of semicryst. polymers is often studied with isothermal expts. and analyzed by fitting the data with anal. expressions of the Avrami and Lauritzen and Hoffman (LH) theories. To correctly carry out the anal., precautions in both expts. and data fitting should be taken. Here, we systematically discussed the factors that influence the validity of the crystn. kinetics study. The basic concepts and fundamentals of the Avrami and LH theories were introduced at first. Then, exptl. protocols were discussed in detail. To clarify the impact of various exptl. parameters, selected common polymers, i.e., polypropylene and polylactide, were studied using various exptl. techniques (i.e., differential scanning calorimetry and polarized light optical microscopy). Common mistakes were simulated under conditions when non-ideal exptl. parameters were applied. Furthermore, from a practical point of view, we show how to fit the exptl. data to the Avrami and the LH theories, using an Origin App developed by us.
  37. 37
    Müller, A. J.; Balsamo, V.; Arnal, M. L. Nucleation and Crystallization in Diblock and Triblock Copolymers. Adv. Polym. Sci. 2005, 190, 1– 63
    Google Scholar
    37
    Nucleation and crystallization in diblock and triblock copolymers
    Muller, Alejandro J.; Balsamo, Vittoria; Arnal, Maria Luisa
    Advances in Polymer Science (2005), 190 (Block Copolymers II), 1-63CODEN: APSIDK; ISSN:0065-3195. (Springer GmbH)
    A review. Crystn. of block copolymer microdomains can have a tremendous influence on the morphol., properties and applications of these materials. In this review, particular emphasis is placed on the nucleation, crystn., thermal properties, and morphol. of diblock and triblock copolymers with one or two crystallizable components. The issues of the different types of nucleation processes (i.e., homogeneous nucleation and heterogeneous nucleation by different types of heterogeneities and surface nucleation) and their relation to the crystn. kinetics of the components is addressed in detail in a wide range of polymeric materials for droplet dispersions, blends, and block copolymers. The case of AB double cryst. diblock copolymers is discussed in the light of recent works on biodegradable systems, while the nucleation, crystn. and morphol. of more complex materials like ABC triblock copolymers with one or 2 crystallizable components are thoroughly reviewed.
  38. 38
    Balsamo, V.; Urdaneta, N.; Pérez, L.; Carrizales, P.; Abetz, V.; Müller, A. J. Effect of the Polyethylene Confinement and Topology on Its Crystallisation within Semicrystalline ABC Triblock Copolymers. Eur. Polym. J. 2004, 40, 1033– 1049,  DOI: 10.1016/j.eurpolymj.2004.01.009
    Google Scholar
    38
    Effect of the polyethylene confinement and topology on its crystallization within semicrystalline ABC triblock copolymers
    Balsamo, V.; Urdaneta, N.; Perez, L.; Carrizales, P.; Abetz, V.; Muller, A. J.
    European Polymer Journal (2004), 40 (6), 1033-1049CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Science B.V.)
    The isothermal crystn. behavior of the polyethylene block within polystyrene-b-polyethylene-b-poly(.vepsiln.-caprolactone), SEC, triblock copolymers was studied by differential scanning calorimetry. The morphol. was obsd. by transmission electron microscopy. Melting scans after isothermal crystn. performed at different times were employed to det. the crystn. kinetics one step at a time ("isothermal step crystn."). Double melting endotherms were obsd. after isothermal crystn. and they were interpreted as a result of the melting of two lamellar populations. These arise from the intrinsic short chain branching distribution within the hydrogenated polybutadiene chains that conform the PE blocks and from their location within the copolymer microdomains. The Hoffman-Weeks procedure failed to yield reasonable values for the equil. m.p. of the PE blocks as a result of the distribution of linear sequences present in these blocks. The results indicate that as the degree of PE confinement increases the Avrami index decreases to values that are even lower than 1, a result that can be explained by the nature of the homogeneous nucleation process that is in between sporadic and instantaneous.

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  • Abstract

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    Figure 1

    Figure 1. Thermotropic phase behavior of PFO. (A) Thermal protocol employed for the experiment. Relevant temperatures: annealing temperature, Ta, glass transition temperature, Tg, melting temperature, Tm, and nematic-to-isotropic transition temperature, TLC-I. (B) FSC heating traces (at 4000 °C/s) following the isothermal step of 1 h at temperatures ranging from Ta = 40 to 160 °C. Endothermic peaks shadowed in purple-cyan and orange correspond to the enthalpic relaxation of the glassy phase, the melting of crystals, and the nematic–isotropic transition, respectively.

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    Figure 2

    Figure 2. Crystallization from an ISO state (left column) and from a NEM state (right column) for varying times. (A and B) Thermal protocols used, where Ta is the annealing temperature, TLC is the temperature at which the liquid crystal develops, Tm is the melting temperature, t is the annealing time, and tsat is the annealing time when the degree of crystallization reaches saturation. (C and D) FSC heating traces (analysis scans); the progression of time is illustrated by the color scale inside the arrow. (E and F) Advance of crystallization (from normalized enthalpy values) with time at the indicated temperatures and their corresponding Avrami fits. t and to are the annealing time and the induction time, respectively.

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    Figure 3

    Figure 3. Experimental results and Avrami parameters as a function of crystallization temperature. (A) Experimental values of the inverse of crystallization times (1/τ50% and 1/τ20%) for different conversions, (B) Avrami index (n), (C) Specific heat capacity for the longest crystallization time times the mass (Cp·m) (i.e., a proxy for the final degree of crystallinity because m is kept constant in the entire experiment), and (D) isothermal crystallization rate obtained from the Avrami model (k1/n).

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    Figure 4

    Figure 4. (A) AFM-height images of PFO crystallized at Ta = 80 °C from an ISO state. (B) AFM-height images of PFO crystallized Ta = 80 °C from a NEM state. (C) Height histograms obtained from A and B AFM data. Height distributions in (C) are fitted to Gaussian curves.

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    Figure 5

    Figure 5. Photoluminescence spectra of crystallized FSC thin-film samples at Ta = 80 °C from an ISO state (blue) and from a NEM state (green).

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  • References

    This article references 38 other publications.

    1. 1
      Ariu, M.; Lidzey, D. G.; Lavrentiev, M.; Bradley, D. D. C.; Jandke, M.; Strohriegl, P. Study of the Different Structural Phases of the Polymer Poly(9,9′-Dioctyl Fluorene) Using Raman Spectroscopy. Synth. Met. 2001, 116, 217– 221,  DOI: 10.1016/s0379-6779(00)00456-2
      1
      A study of the different structural phases of the polymer poly(9,9'-dioctylfluorene) using Raman spectroscopy
      Ariu, M.; Lidzey, D. G.; Lavrentiev, M.; Bradley, D. D. C.; Jandke, M.; Strohriegl, P.
      Synthetic Metals (2001), 116 (1-3), 217-221CODEN: SYMEDZ; ISSN:0379-6779. (Elsevier Science S.A.)
      The polymer poly(9,9-dioctylfluorene) (F8) can be easily driven between a no. of different structural phases by different thermal or solvent treatments. The phases which the authors have identified include (i) as-spin-coated, (ii) semi-cryst., (iii) glassy, (iv) with an extended intrachain conformation. At. force microscopy was used to investigate the surface structures assocd. with the different phases of the polymer and different solvents used to cast the film. Raman spectroscopy was performed on these samples to understand how the polymer conformation changes with the phases. Variations in the relative intensity of the peaks and shifts in energy are obsd. The authors have compared the F8 spectrum with a trimer of fluorene with Bu side chains and acrylate/hydroxy end-groups attached to the fluorene main chain via hexyl spacers. They identify a very small frequency dispersion in the vibrational modes connected to an increase of the conjugation length. Therefore, the assignment of the vibrational modes of the trimer is very important for understanding the F8 spectrum.
    2. 2
      Jimison, L. H.; Toney, M. F.; McCulloch, I.; Heeney, M.; Salleo, A. Charge-Transport Anisotropy Due to Grain Boundaries in Directionally Crystallized Thin Films of Regioregular Poly(3-Hexylthiophene). Adv. Mater. 2009, 21, 1568– 1572,  DOI: 10.1002/adma.200802722
      2
      Charge-Transport Anisotropy Due to Grain Boundaries in Directionally Crystallized Thin Films of Regioregular Poly(3-hexylthiophene)
      Jimison, Leslie H.; Toney, Michael F.; McCulloch, Iain; Heeney, Martin; Salleo, Alberto
      Advanced Materials (Weinheim, Germany) (2009), 21 (16), 1568-1572CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A directional crystn. technique was used to produce poly(3-hexylthiophene) (P3HT) films that are highly anisotropic in plane, to study the charge-transport properties of grain boundaries between different orientations of crystallites. Boundaries along the fiber provide a small barrier to charge transport when compared to fiber-to-fiber grain boundaries. In these in-line grain boundaries, relatively straight polymer mols. provide an easy intergranular charge-transport path. Fiber-to-fiber grain boundaries act as large transport barriers, because intergranular chains cannot exist without sharp bends or twists, thus decreasing elec. connectivity. The data help to solidify the hypothesis that in low-angle grain boundaries transport is easier only in the direction parallel to the polymer backbone, due to bridging mols. Optimization of the microstructure in electronic devices should therefore not focus solely on the elimination of grain boundaries, but also include efforts to control grain-boundary placement and relative grain orientation.
    3. 3
      Yang, H.; Shin, T. J.; Yang, L.; Cho, K.; Ryu, C. Y.; Bao, Z. Effect of Mesoscale Crystalline Structure on the Field-Effect Mobility of Regioregular Poly(3-Hexyl Thiophene) in Thin-Film Transistors. Adv. Funct. Mater. 2005, 15, 671– 676,  DOI: 10.1002/adfm.200400297
      3
      Effect of mesoscale crystalline structure on the field-effect mobility of regioregular poly(3-hexyl thiophene) in thin-film transistors
      Yang, Hoichang; Shin, Tae Joo; Yang, Lin; Cho, Kilwon; Ryu, Chang Y.; Bao, Zhenan
      Advanced Functional Materials (2005), 15 (4), 671-676CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Regioregular poly(3-hexylthiophene) (RR P3HT) is drop-cast to fabricate field-effect transistor (FET) devices from different solvents with different b.ps. and solubilities for RR P3HT, such as methylene chloride, toluene, THF, and chloroform. A Petri dish is used to cover the soln., and it takes less than 30 min for the solvents to evap. at room temp. The mesoscale cryst. morphol. of RR P3HT thin films can be manipulated from well-dispersed nanofibrils to well-developed spherulites by changing soln. processing conditions. The morphol. correlation with the charge-carrier mobility in RR P3HT thin-film transistor (TFT) devices is investigated. The TFT devices show charge-carrier mobilities in the range of 10-4-10-2 cm2V-1s-1 depending on the solvent used, although grazing-incidence X-ray diffraction (GIXD) reveals that all films develop the same π-π-stacking orientation, where the <100>-axis is normal to the polymer films. By combining results from at. force microscopy (AFM) and GIXD, it is found that the morphol. connectivity of cryst. nanofibrils and the <100>-axis orientation distribution of the π-π-stacking plane with respect to the film normal play important roles on the charge-carrier mobility of RR P3HT for TFT applications.
    4. 4
      Noriega, R.; Rivnay, J.; Vandewal, K.; Koch, F. P. V.; Stingelin, N.; Smith, P.; Toney, M. F.; Salleo, A. A General Relationship between Disorder, Aggregation and Charge Transport in Conjugated Polymers. Nat. Mater. 2013, 12, 1038– 1044,  DOI: 10.1038/nmat3722
      4
      A general relationship between disorder, aggregation and charge transport in conjugated polymers
      Noriega, Rodrigo; Rivnay, Jonathan; Vandewal, Koen; Koch, Felix P. V.; Stingelin, Natalie; Smith, Paul; Toney, Michael F.; Salleo, Alberto
      Nature Materials (2013), 12 (11), 1038-1044CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
      Conjugated polymer chains have many degrees of conformational freedom and interact weakly with each other, resulting in complex microstructures in the solid state. Understanding charge transport in such systems, which have amorphous and ordered phases exhibiting varying degrees of order, has proved difficult owing to the contribution of electronic processes at various length scales. The growing technol. appeal of these semiconductors makes such fundamental knowledge extremely important for materials and process design. We propose a unified model of how charge carriers travel in conjugated polymer films. We show that in high-mol.-wt. semiconducting polymers the limiting charge transport step is trapping caused by lattice disorder, and that short-range intermol. aggregation is sufficient for efficient long-range charge transport. This generalization explains the seemingly contradicting high performance of recently reported, poorly ordered polymers and suggests mol. design strategies to further improve the performance of future generations of org. electronic materials.
    5. 5
      Yu, L.; Davidson, E.; Sharma, A.; Andersson, M. R.; Segalman, R.; Müller, C. Isothermal Crystallization Kinetics and Time-Temperature-Transformation of the Conjugated Polymer: Poly(3-(2′-Ethyl)Hexylthiophene). Chem. Mater. 2017, 29, 5654– 5662,  DOI: 10.1021/acs.chemmater.7b01393
      5
      Isothermal Crystallization Kinetics and Time-Temperature-Transformation of the Conjugated Polymer: Poly(3-(2'-ethyl)hexylthiophene)
      Yu, Liyang; Davidson, Emily; Sharma, Anirudh; Andersson, Mats R.; Segalman, Rachel; Muller, Christian
      Chemistry of Materials (2017), 29 (13), 5654-5662CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Thermal annealing strongly impacts the nano- and microstructure of conjugated polymers. Despite the fundamental importance for the resulting opto-electronic behavior of this class of materials, the underlying crystn. processes have not received the same attention that is encountered in other disciplines of materials science. The question arises whether classical treatment of nucleation and growth phenomena is truly applicable to conjugated polymers. Here, the isothermal crystn. behavior of the conjugated polymer poly(3-(2'-ethyl)hexylthiophene) (P3EHT) is monitored with differential scanning calorimetry (DSC). Avrami anal. reveals growth- and nucleation limited temp. regimes that are sepd. by the max. rate of crystn. The mol. wt. of the polymer is found to strongly influence the abs. rate of crystn. at the same degree of undercooling relative to the melting temp. A combination of optical microscopy and grazing-incidence wide-angle X-ray scattering (GIWAXS) confirms that the resulting nano- and microstructure strongly correlate with the selected isothermal annealing temp. Hence, this work establishes that classical nucleation and growth theory can be applied to describe the solidification behavior of the semi-cryst. conjugated polymer P3EHT.
    6. 6
      Duong, D. T.; Ho, V.; Shang, Z.; Mollinger, S.; Mannsfeld, S. C. B.; Dacuña, J.; Toney, M. F.; Segalman, R.; Salleo, A. Mechanism of Crystallization and Implications for Charge Transport in Poly(3-Ethylhexylthiophene) Thin Films. Adv. Funct. Mater. 2014, 24, 4515– 4521,  DOI: 10.1002/adfm.201304247
      6
      Mechanism of Crystallization and Implications for Charge Transport in Poly(3-ethylhexylthiophene) Thin Films
      Duong, Duc T.; Ho, Victor; Shang, Zhengrong; Mollinger, Sonya; Mannsfeld, Stefan C. B.; Dacuna, Javier; Toney, Michael F.; Segalman, Rachel; Salleo, Alberto
      Advanced Functional Materials (2014), 24 (28), 4515-4521CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
      In this work, crystn. kinetics and aggregate growth of poly(3-ethylhexylthiophene) (P3EHT) thin films are studied as a function of film thickness. X-ray diffraction and optical absorption show that individual aggregates and crystallites grow anisotropically and mostly along only two packing directions: the alkyl stacking and the polymer chain backbone direction. Further, it is also detd. that crystn. kinetics is limited by the reorganization of polymer chains and depends strongly on the film thickness and av. mol. wt. Time-dependent, field-effect hole mobilities in thin films reveal a percolation threshold for both low and high mol. wt. P3EHT. Structural anal. reveals that charge percolation requires bridged aggregates sepd. by a distance of ≈2-3 nm, which is on the order of the polymer persistence length. These results thus highlight the importance of tie mols. and inter-aggregate distance in supporting charge percolation in semiconducting polymer thin films. The study as a whole also demonstrates that P3EHT is an ideal model system for polythiophenes and should prove to be useful for future investigations into crystn. kinetics.
    7. 7
      Zhao, Y.; Yuan, G.; Roche, P.; Leclerc, M. A Calorimetric Study of the Phase Transitions in Poly(3-Hexylthiophene). Polymer 1995, 36, 2211– 2214,  DOI: 10.1016/0032-3861(95)95298-f
      7
      A calorimetric study of the phase transitions in poly(3-hexylthiophene)
      Zhao, Yue; Yuan, Guoxiong; Roche, Philippe; Leclerc, Mario
      Polymer (1995), 36 (11), 2211-14CODEN: POLMAG; ISSN:0032-3861. (Elsevier)
      Differential scanning calorimetry was utilized for investigating the isothermal crystn. of a poly(3-hexylthiophene) (P3HT) sample over a wide range of temps. We found two well sepd. crystal formation processes: a fast process, essentially completed before the sample reaches the isothermal conditions, which produces crystals having higher transition temps. (at around 178°C), and a slow process which leads to continuous growth of less stable crystals, the transition temps. of which are detd. by the crystn. temp., namely, about 32°C above. The slow crystn. process occurs at temps. as low as 40°C. This crystn. behavior supports the suggestion that a nematic state exists in the melt of P3HT.
    8. 8
      Pal, S.; Nandi, A. K. Cocrystallization Mechanism of Poly(3-Hexyl Thiophenes) with Different Amount of Chain Regioregularity. J. Appl. Polym. Sci. 2006, 101, 3811– 3820,  DOI: 10.1002/app.24067
      8
      Cocrystallization mechanism of poly(3-hexyl thiophenes) with different amount of chain regioregularity
      Pal, Susmita; Nandi, Arun K.
      Journal of Applied Polymer Science (2006), 101 (6), 3811-3820CODEN: JAPNAB; ISSN:0021-8995. (John Wiley & Sons, Inc.)
      The overall crystn. rates of poly(3-hexyl thiophene) (P3HT) cocrystals with different amt. of regioregularity of the components are measured using differential scanning calorimetry (DSC). Two pairs of cocrystals with varying compns. of the component polymers (viz P3HT(R) (regioregularity 92 mol%)/P3HT-2 (regioregularity 82 mol%), and P3HT-2/P3HT-1 (regioregularity 75 mol%)) are used. The crystn. rate at the same isothermal crystn. temp. (Tc) decreases with increasing regioregularity. The low Avrami exponent values (0.15-1.0) in all the samples suggest the presence of rigid amorphous portion, which cannot diffuse out quickly from the crystal growth front (soft impingement). Anal. of crystn. rate using Laurintzen-Hoffman (L-H) growth rate theory indicates Regime I to Regime II transition in all the samples. The product of lateral and end surface energy values (σσe) increases gradually with increasing regioirregularity in the blend. Anal. of σ values indicates chain extension of the components in the melt of the blend and the entropy of activation (ΔSI-II) of the cocrystals are higher than those of the components. The entropy of cocrystn. (ΔSc) values are 1-2.4 e.u for P3HT(R)/P3HT-2 system and 0.5-1 e.u for P3HT-2/P3HT-1 system.
    9. 9
      Yang, G. Z.; Chen, X.; Wang, W.; Wang, M.; Liu, T.; Li, C. Z. Nonisothermal Crystallization and Melting Behavior of a Luminescent Conjugated Polymer, Poly(9,9-Dihexylfluorene-Alt-Co-2,5-Didecyloxy-1,4- Phenylene). J. Polym. Sci. Part B Polym. Phys. 2007, 45, 976– 987,  DOI: 10.1002/polb.21110
      9
      Nonisothermal crystallization and melting behavior of a luminescent conjugated polymer, poly(9,9-dihexylfluorene-alt-co-2,5-didecyloxy-1,4-phenylene)
      Yang, Gui-Zhong; Chen, Xiaolei; Wang, Weizhi; Wang, Min; Liu, Tianxi; Li, Chun-Zhong
      Journal of Polymer Science, Part B: Polymer Physics (2007), 45 (8), 976-987CODEN: JPBPEM; ISSN:0887-6266. (John Wiley & Sons, Inc.)
      The nonisothermal crystn. kinetics of a luminescent conjugated polymer, poly(9,9-dihexylfluorene-alt-co-2,5-didecyloxy-1,4-phenylene) (PF6OC10) with three different mol. wts. was studied by differential scanning calorimetry under different cooling rates from the melt. With increasing mol. wt. of PF6OC10, the temp. range of crystn. peak steadily became narrower and shifted to higher temp. region and the crystn. rate increased. The Ozawa method failed to describe the nonisothermal crystn. behavior of PF6OC10. Although the Avrami method did not effectively describe the nonisothermal crystn. kinetics of PF6OC10 for overall process, it was valid for describing the early stage of crystn. with an Avrami exponent n of about 3. The combined method, proposed by the authors was able to satisfactorily describe the nonisothermal crystn. behavior of PF6OC10. The crystn. activation energy detd. by Kissinger, Takhor, and Augis-Bennett models were comparable. The melting temp. of PF6OC10 increased with increasing mol. wt. For a low-mol.-wt. sample, PF6OC10 showed double melting phenomenon. The interval between the two melting peaks decreased with increasing mol. wt., and only one melting peak was obsd. for the high-mol.-wt. sample.
    10. 10
      Chen, X. L.; Huang, H. L.; Shi, J. G.; Liu, Y. L.; Wang, L. M. Isothermal Crystallization Kinetics and Melting Behavior of a Luminescent Conjugated Polymer, Poly(9,9-Dihexylfluorene-Alt-2,5-Didodecyloxybenzene). J. Macromol. Sci. Part B Phys. 2012, 51, 1049– 1056,  DOI: 10.1080/00222348.2011.625883
      10
      Isothermal Crystallization Kinetics and Melting Behavior of a Luminescent Conjugated Polymer, Poly(9,9-Dihexylfluorene-Alt-2,5-Didodecyloxybenzene)
      Chen, Xiao-Lei; Huang, Hong-Liang; Shi, Jian-Gao; Liu, Yong-Li; Wang, Lu-Min
      Journal of Macromolecular Science, Part B: Physics (2012), 51 (6), 1049-1056CODEN: JMAPBR; ISSN:0022-2348. (Taylor & Francis, Inc.)
      A study of the isothermal crystn. behaviors of poly(9,9-dihexylfluorene-alt-2,5-didodecyloxybenzene) (PF6OC12) was carried out using differential scanning calorimetry (DSC). The crystn. kinetics under isothermal conditions could be described by the Avrami equation. The Avrami exponent n ranges from 3.43 to 3.71 for PF6OC12 at crystn. temps. between 100.0°C and 90.0°C, indicating a three-dimensional spherical crystal growth with homogeneous nucleation in the primary crystn. stage for the isothermal melt crystn. process. In the DSC scan, after the isothermal crystn., multiple melting behavior was found. The multiple endotherms could be attributed to melting of recrystd. materials produced originally during different crystn. processes. According to the Arrhenius equation, the activation energy was detd. to be 211.29 kJmol-1 for the isothermal melt crystn. of PF6OC12.
    11. 11
      Chen, S. H.; Wu, Y. H.; Su, C. H.; Jeng, U.; Hsieh, C. C.; Su, A. C.; Chen, S. A. Cold Crystallization of Poly(9,9-Di-n-Octyl-2,7-Fluorene). Macromolecules 2007, 40, 5353– 5359,  DOI: 10.1021/ma070237g
      11
      Cold Crystallization of Poly(9,9-di-n-octyl-2,7-fluorene)
      Chen, S. H.; Wu, Y. H.; Su, C. H.; Jeng, U.; Hsieh, C. C.; Su, A. C.; Chen, S. A.
      Macromolecules (Washington, DC, United States) (2007), 40 (15), 5353-5359CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      We have previously demonstrated that soln.-cast films of conjugated polymers with grafted alkyl side chains comprise clearly identifiable domains ca. 10 nm in size upon solvent evapn. Here we show that these nanodomains indeed serve as basic units for morphol. development in poly(9,9-di-n-octyl-2,7-fluorene) (PFO) films during cold crystn. Results of our microscopic and diffraction observations indicate that the cold crystn. process involves intradomain nucleation and growth, followed by nanodomain alignment and coalescence into fibrils in the sub-micrometer length scale via thermally activated adjustment of nanodomain orientation. An analogy with oriented aggregation (or oriented attachment-coalescence) behavior of nanocrystals of metal oxides is drawn; the relevance to recently proposed models of polymer crystn. via primary nucleation induced at the growth front is addressed.
    12. 12
      Yang, G. Z.; Chen, X.; Xu, Y.; Li, C. Z.; Wu, P.; Liu, T. Nonisothermal Crystallization Behavior of a Luminescent Conjugated Polymer, Poly(9,9-Dihexylfluorene-Alt-2,5-Didodecyloxybenzene). Polym. Int. 2007, 56, 245– 251,  DOI: 10.1002/pi.2147
      12
      Nonisothermal crystallization behavior of a luminescent conjugated polymer, poly(9,9-dihexylfluorene-alt-2,5-didodecyloxybenzene)
      Yang, Gui-Zhong; Chen, Xiaolei; Xu, Yan; Li, Chun-Zhong; Wu, Peiyi; Liu, Tianxi
      Polymer International (2007), 56 (2), 245-251CODEN: PLYIEI; ISSN:0959-8103. (John Wiley & Sons Ltd.)
      The nonisothermal crystn. kinetics of poly(9,9-dihexylfluorene-alt-2,5-didodecyloxybenzene) (PF6OC12) from the melt were investigated using differential scanning calorimetry under different cooling rates. Several anal. methods were used to describe the nonisothermal crystn. behavior of PF6OC12. It was found that the modified Avrami method by Jeziorny was only valid for describing the early stage of crystn. but was not able to describe the later stage of PF6OC12 crystn. Also, the Ozawa method failed to describe the nonisothermal crystn. behavior of PF6OC12. However, the method developed by combining the Avrami and Ozawa equations could successfully describe the nonisothermal crystn. kinetics of PF6OC12. According to the Kissinger method, the activation energy was detd. to be 114.9 kJ mol-1 for the nonisothermal melt crystn. of PF6OC12.
    13. 13
      Perevedentsev, A.; Stavrinou, P. N.; Bradley, D. D. C.; Smith, P. Solution-Crystallization and Related Phenomena in 9,9-Dialkyl-Fluorene Polymers. I. Crystalline Polymer-Solvent Compound Formation for Poly(9,9-Dioctylfluorene). J. Polym. Sci. Part B Polym. Phys. 2015, 53, 1481– 1491,  DOI: 10.1002/polb.23798
      13
      Solution-crystallization and related phenomena in 9,9-dialkyl-fluorene polymers. I. Crystalline polymer-solvent compound formation for poly(9,9-dioctylfluorene)
      Perevedentsev, Aleksandr; Stavrinou, Paul N.; Bradley, Donal D. C.; Smith, Paul
      Journal of Polymer Science, Part B: Polymer Physics (2015), 53 (21), 1481-1491CODEN: JPBPEM; ISSN:0887-6266. (John Wiley & Sons, Inc.)
      Polymer-solvent compd. formation, occurring via co-crystn. of polymer chains and selected small-mol. species, is demonstrated for the conjugated polymer poly(9,9-dioctylfluorene) (PFO) and a range of org. solvents. The resulting crystn. and gelation processes in PFO solns. are studied by differential scanning calorimetry, with X-ray diffraction providing addnl. information on the resulting microstructure. It is shown that PFO-solvent compds. comprise an ultra-regular mol.-level arrangement of the semiconducting polymer host and small-mol. solvent guest. Crystals form following adoption of the planar-zigzag β-phase chain conformation, which, due to its geometry, creates periodic cavities that accommodate the ordered inclusion of solvent mols. of matching vol. The findings are formalized in terms of nonequil. temp.-compn. phase diagrams. The potential applications of these compds. and the new functionalities that they might enable are also discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015.
    14. 14
      Bridges, C. R.; Ford, M. J.; Bazan, G. C.; Segalman, R. A. Molecular Considerations for Mesophase Interaction and Alignment of Lyotropic Liquid Crystalline Semiconducting Polymers. ACS Macro Lett. 2017, 6, 619– 624,  DOI: 10.1021/acsmacrolett.7b00273
      14
      Molecular Considerations for Mesophase Interaction and Alignment of Lyotropic Liquid Crystalline Semiconducting Polymers
      Bridges, Colin R.; Ford, Michael J.; Bazan, Guillermo C.; Segalman, Rachel A.
      ACS Macro Letters (2017), 6 (6), 619-624CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
      Intermol. interactions in conjugated polymers influence crystallinity, self-assembly, and packing motif, factors which in turn crucially impact charge transport properties such as carrier mobility in org. electronic devices. Correlated alignment of mol. and cryst. morphologies provides direct pathways for charge carriers to follow; however, the role of intermol. interactions in achieving this is unexplored. Herein, we synthesize a series of lyotropic liq. cryst. conjugated polymers with variable side-chain structure to lend distinct steric repulsion and van der Waals attractive forces to each mesophase. We use this to study the role of intermol. interactions on mesophase alignment. The strength of intermol. interaction for each mesophase is compared by measuring melting temp., π-stacking distance, and the Maier-Saupe interaction parameter. In general we find that side-chain structure can impact interaction strength by varying steric repulsion and backbone attractions and that the Maier-Saupe interaction parameters correlate with higher degrees of alignment after shearing, achieving a dichroic absorbance ratio of up to 2. This observation is used to develop equil. processing methods for fabricating macroscopically aligned polymer substrates used in transistors, improving mobility by a factor of 3 compared to spin-coated devices.
    15. 15
      Zhang, L.; Zhao, K.; Li, H.; Zhang, T.; Liu, D.; Han, Y. Liquid Crystal Ordering on Conjugated Polymers Film Morphology for High Performance. J. Polym. Sci. Part B Polym. Phys. 2019, 57, 1572– 1591,  DOI: 10.1002/polb.24885
      15
      Liquid Crystal Ordering on Conjugated Polymers Film Morphology for High Performance
      Zhang, Lu; Zhao, Kefeng; Li, Hongxiang; Zhang, Tao; Liu, Duo; Han, Yanchun
      Journal of Polymer Science, Part B: Polymer Physics (2019), 57 (23), 1572-1591CODEN: JPBPEM; ISSN:0887-6266. (John Wiley & Sons, Inc.)
      A review. The electronic performance of conjugated polymers depends on the microstructure of the polymer films. A percolated network morphol. with high crystallinity, ordered intermol. packing and long-range order is beneficial for charge transport. In recent reports, some conjugated polymers have been shown to exhibit liq. crystallinity. The appearance of liq. cryst. ordering provides a new soln. to solve the difficulties in microstructure manipulation. In this review, we summarize how liq. crystallinity can assist mol. arrangement and guide long-range orientation during film processing, leading to high charge mobility. We expect that this article could draw more attention to the liq. crystallinity of conjugated polymers.
    16. 16
      McCulloch, I.; Heeney, M.; Bailey, C.; Genevicius, K.; MacDonald, I.; Shkunov, M.; Sparrowe, D.; Tierney, S.; Wagner, R.; Zhang, W.; Chabinyc, M. L.; Kline, R. J.; McGehee, M. D.; Toney, M. F. Liquid-Crystalline Semiconducting Polymers with High Charge-Carrier Mobility. Nat. Mater. 2006, 5, 328– 333,  DOI: 10.1038/nmat1612
      16
      Liquid-crystalline semiconducting polymers with high charge-carrier mobility
      McCulloch, Iain; Heeney, Martin; Bailey, Clare; Genevicius, Kristijonas; MacDonald, Iain; Shkunov, Maxim; Sparrowe, David; Tierney, Steve; Wagner, Robert; Zhang, Weimin; Chabinyc, Michael L.; Kline, R. Joseph; McGehee, Michael D.; Toney, Michael F.
      Nature Materials (2006), 5 (4), 328-333CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
      Org. semiconductors that can be fabricated by simple processing techniques and possess excellent elec. performance, are key requirements in the progress of org. electronics. Both high semiconductor charge-carrier mobility, optimized through understanding and control of the semiconductor microstructure, and stability of the semiconductor to ambient electrochem. oxidative processes are required. The authors report on new semiconducting liq.-cryst. thieno[3,2-b ]thiophene polymers, the enhancement in charge-carrier mobility achieved through highly organized morphol. from processing in the mesophase, and the effects of exposure to both ambient and low-humidity air on the performance of transistor devices. Relatively large cryst. domain sizes on the length scale of lithog. accessible channel lengths (∼200 nm) were exhibited in thin films, thus offering the potential for fabrication of single-crystal polymer transistors. Good transistor stability under static storage and operation in a low-humidity air environment was demonstrated, with charge-carrier field-effect mobilities of 0.2-0.6 cm2 V-1 s-1 achieved under nitrogen.
    17. 17
      Bridges, C. R.; Ford, M. J.; Popere, B. C.; Bazan, G. C.; Segalman, R. A. Formation and Structure of Lyotropic Liquid Crystalline Mesophases in Donor-Acceptor Semiconducting Polymers. Macromolecules 2016, 49, 7220– 7229,  DOI: 10.1021/acs.macromol.6b01650
      17
      Formation and Structure of Lyotropic Liquid Crystalline Mesophases in Donor-Acceptor Semiconducting Polymers
      Bridges, Colin R.; Ford, Michael J.; Popere, Bhooshan C.; Bazan, Guillermo C.; Segalman, Rachel A.
      Macromolecules (Washington, DC, United States) (2016), 49 (19), 7220-7229CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Controlling crystallinity and mol. packing at nano- and macroscopic length scales in conjugated polymer thin films is vital for improving the performance of polymer-based electronic devices. Herein, the inherent amphiphilicity of rigid donor-acceptor copolymers used in high performance polymer electronics is leveraged to allow the formation of highly ordered lyotropic mesophases. By increasing the length and branching of solubilizing chains on cyclopentadithiophene-alt-thiadiazolopyridine-based alternating copolymers, amphiphilicity can be increased, and lyotropic liq. cryst. mesophases are obsd. in selective solvents. These lyotropic mesophases consist of chain extended polymers exhibiting close, ordered π-stacking. This is evidenced by birefringent solns. and red-shifted absorbance spectra displaying pronounced excitonic coupling. Crystallinity developed in soln. can be transferred to the solid state, and thin films of donor-acceptor copolymers cast from lyotropic solns. exhibit improved cryst. order in both the alkyl and π-stacking directions. Because of this improved crystallinity, transistors with active layers cast from lyotropic solns. exhibit a significant improvement in carrier mobility compared to those cast from isotropic soln., reaching a max. value of 0.61 cm2 V-1 s-1. This approach of rational side chain design bridges the gap from soln. structure to solid state structure and is a promising and general approach to allow the expression of lyotropic mesophases in rigid conjugated polymers.
    18. 18
      Marina, S.; Gutierrez-Fernandez, E.; Gutierrez, J.; Gobbi, M.; Ramos, N.; Solano, E.; Rech, J.; You, W.; Hueso, L. E.; Tercjak, A.; Ade, H.; Martin, J. Semi-Paracrystallinity in Semi-Conducting Polymers. Mater. Horizons 2022, 9, 1196– 1206,  DOI: 10.1039/d1mh01349a
      18
      Semi-paracrystallinity in semi-conducting polymers
      Marina, Sara; Gutierrez-Fernandez, Edgar; Gutierrez, Junkal; Gobbi, Marco; Ramos, Nicolas; Solano, Eduardo; Rech, Jeromy; You, Wei; Hueso, Luis; Tercjak, Agnieszka; Ade, Harald; Martin, Jaime
      Materials Horizons (2022), 9 (4), 1196-1206CODEN: MHAOBM; ISSN:2051-6355. (Royal Society of Chemistry)
      Precise detn. of structural organization of semi-conducting polymers is of paramount importance for the further development of these materials in org. electronic technologies. Yet, prior characterization of some of the best-performing materials for transistor and photovoltaic applications, which are based on polymers with rigid backbones, often resulted in conundrums in which X-ray scattering and microscopy yielded seemingly contradicting results. Here we solve the paradox by introducing a new structural model, i.e., semi-paracryst. organization. The model establishes that the microstructure of these materials relies on a dense array of small paracryst. domains embedded in a more disordered matrix. Thus, the overall structural order relies on two parameters: the novel concept of degree of paracrystallinity (i.e., paracryst. vol./mass fraction, introduced here for the first time) and the lattice distortion parameter of paracryst. domains (g-parameter from X-ray scattering). Structural parameters of the model are correlated with long-range charge carrier transport, revealing that charge transport in semi-paracryst. materials is particularly sensitive to the interconnection of paracryst. domains.
    19. 19
      Liu, X.; Huettner, S.; Rong, Z.; Sommer, M.; Friend, R. H. Solvent Additive Control of Morphology and Crystallization in Semiconducting Polymer Blends. Adv. Mater. 2012, 24, 669– 674,  DOI: 10.1002/adma.201103097
      19
      Solvent Additive Control of Morphology and Crystallization in Semiconducting Polymer Blends
      Liu, Xueliang; Huettner, Sven; Rong, Zhuxia; Sommer, Michael; Friend, Richard H.
      Advanced Materials (Weinheim, Germany) (2012), 24 (5), 669-674CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      BrAni (4-bromoanisole) is an effective and versatile solvent additive for promoting P3HT crystn. during processing of different P3HT-contg. blends is demonstrated. The mechanism is attributed to its lower volatility than the principal solvent, and its selective soly. as confirmed with studies of absorption spectra and solvent-vapor swelling isotherms. Furthermore, P3HT crystn. induced during film formation can reduce the dependence of morphol. on the often different natural demixing behavior of various P3HT blends, there by allowing pure, ordered and interpenetrating domains close to the ideal size to be formed for a no. of different acceptor choices. This improved morphol. in turn led to enhanced OPV performance than using conventional thermal annealing alone, particularly for polymer-polymer systems. Finally, we draw attention to the defining role that the design and development of new conjugated semiconducting polymers has made in this field.
    20. 20
      Liu, Y.; Zhao, J.; Li, Z.; Mu, C.; Ma, W.; Hu, H.; Jiang, K.; Lin, H.; Ade, H.; Yan, H. Aggregation and Morphology Control Enables Multiple Cases of High-Efficiency Polymer Solar Cells. Nat. Commun. 2014, 5, 1– 8,  DOI: 10.1038/ncomms6293
      There is no corresponding record for this reference.
    21. 21
      Luzio, A.; Nübling, F.; Martin, J.; Fazzi, D.; Selter, P.; Gann, E.; McNeill, C. R.; Brinkmann, M.; Hansen, M. R.; Stingelin, N.; Sommer, M.; Caironi, M. Microstructural Control Suppresses Thermal Activation of Electron Transport at Room Temperature in Polymer Transistors. Nat. Commun. 2019, 10, 3365,  DOI: 10.1038/s41467-019-11125-9
      21
      Microstructural control suppresses thermal activation of electron transport at room temperature in polymer transistors
      Luzio Alessandro; Caironi Mario; Nubling Fritz; Sommer Michael; Martin Jaime; Martin Jaime; Fazzi Daniele; Selter Philipp; Hansen Michael Ryan; Gann Eliot; McNeill Christopher R; Gann Eliot; Gann Eliot; Brinkmann Martin; Stingelin Natalie
      Nature communications (2019), 10 (1), 3365 ISSN:.
      Recent demonstrations of inverted thermal activation of charge mobility in polymer field-effect transistors have excited the interest in transport regimes not limited by thermal barriers. However, rationalization of the limiting factors to access such regimes is still lacking. An improved understanding in this area is critical for development of new materials, establishing processing guidelines, and broadening of the range of applications. Here we show that precise processing of a diketopyrrolopyrrole-tetrafluorobenzene-based electron transporting copolymer results in single crystal-like and voltage-independent mobility with vanishing activation energy above 280 K. Key factors are uniaxial chain alignment and thermal annealing at temperatures within the melting endotherm of films. Experimental and computational evidences converge toward a picture of electrons being delocalized within crystalline domains of increased size. Residual energy barriers introduced by disordered regions are bypassed in the direction of molecular alignment by a more efficient interconnection of the ordered domains following the annealing process.
    22. 22
      Padmaja, S.; Ajita, N.; Srinivasulu, M.; Girish, S. R.; Pisipati, V. G. K. M.; Potukuchi, D. M. Crystallization Kinetics in Liquid Crystals with Hexagonal Precursor Phases by Calorimetry. Zeitschrift fur Naturforsch. - Sect. A J. Phys. Sci. 2010, 65, 733– 744,  DOI: 10.1515/zna-2010-8-916
      There is no corresponding record for this reference.
    23. 23
      Carpaneto, L.; Marsano, E.; Valenti, B.; Zanardi, G. Crystallization and Melting Behaviour of a Semirigid Liquid-Crystalline Polyester. Polymer 1992, 33, 3865– 3872,  DOI: 10.1016/0032-3861(92)90374-6
      23
      Crystallization and melting behavior of a semirigid liquid-crystalline polyester
      Carpaneto, L.; Marsano, E.; Valenti, B.; Zanardi, G.
      Polymer (1992), 33 (18), 3865-72CODEN: POLMAG; ISSN:0032-3861.
      DSC was used to investigate the thermal behavior of a mesogenic polyester built up of a flexible spacer of 8 CH2 units and a rigid arom. ester triad. Nonisothermal crystns. at different cooling rates and isothermal crystns. at various temps. were carried out; the variations of the melting temps. and enthalpies as a function of the crystn. parameters were investigated. The melting profiles of the treated samples reveal 2 endotherms at temps. Tm1 and Tm2, which could not be interpreted as usually reported for conventional polymers. A new model of crystn. was proposed, taking into account that a certain registry of neighboring chains persists in the nematic state above Tm, and becomes poorer and poorer on increasing the temp. and time; this persistent registry can be regarded as potential nuclei of crystn., responsible for the high-temp. endotherm. Therefore, the presence of multiple endotherms in the melting profile of thermotropic polymers crystd. from the liq.-cryst. state appears to be a consequence of the annealing conditions in the nematic phase.
    24. 24
      Katerska, B.; Exner, G.; Perez, E.; Krasteva, M. N. Cooling Rate Effect on the Phase Transitions in a Polymer Liquid Crystal: DSC and Real-Time MAXS and WAXD Experiments. Eur. Polym. J. 2010, 46, 1623– 1632,  DOI: 10.1016/j.eurpolymj.2010.03.018
      24
      Cooling rate effect on the phase transitions in a polymer liquid crystal: DSC and real-time MAXS and WAXD experiments
      Katerska, Borislava; Exner, Ginka; Perez, Ernesto; Krasteva, Manya N.
      European Polymer Journal (2010), 46 (7), 1623-1632CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Ltd.)
      The importance of the cooling rate for the structural transformations in a main-chain poly(hexamethylene-4,4'-bibenzoate) was presented. Detailed anal. of the phase transitions, main structural parameters and their temp. changes was performed by differential scanning calorimetry, real-time middle-angle x-ray scattering and wide-angle x-ray diffraction methods. The thermodn. nature of the initial transformation into a smectic A phase was discussed. The material in the smectic state is supposed to be organized in smectic domains. The crystn. from the smectic phase depends strongly on the kinetics. The crystn. inside the smectic domains results into different final structures detd. by the cooling rate applied. At the highest cooling rates, only one cryst. form was obsd. Different possible modifications were discussed for the case: either a γ-polymorphic form or still some mesophase of high order, as a frozen metastable state. There is a possibility that the phase might be also identified as a condis crystal. At decreasing cooling rates, a new cryst. form, named α*, appears together with the first one. Lowering the cooling rate, the vol. fraction of the α*-polymorph gradually increases, at the expenses of the first form. The interesting feature of the new obsd. α*-polymorph is that it has some similarities with α- and δ-phases of the same material. Contrary to the previous observations, no γ ⇔α* transformation was obsd. neither during the course of single crystn. nor during the subsequent heating. A model describing the gradual transformation of the material during its temp. treatment was proposed.
    25. 25
      Androsch, R.; Soccio, M.; Lotti, N.; Cavallo, D.; Schick, C. Cold-Crystallization of Poly(Butylene 2,6-Naphthalate) Following Ostwald’s Rule of Stages. Thermochim. Acta 2018, 670, 71– 75,  DOI: 10.1016/j.tca.2018.10.015
      25
      Cold-crystallization of poly(butylene 2,6-naphthalate) following Ostwald's rule of stages
      Androsch, Rene; Soccio, Michelina; Lotti, Nadia; Cavallo, Dario; Schick, Christoph
      Thermochimica Acta (2018), 670 (), 71-75CODEN: THACAS; ISSN:0040-6031. (Elsevier B.V.)
      Melt-crystn. of poly (butylene 2,6-naphthalate) (PBN) at temps. lower than about 160 °C follows Ostwald's rule of stages, leading first to formation of a transient smectic liq. cryst. phase (LC) which then may convert in a second step into crystals, controlled by kinetics. In the present work, the PBN melt was cooled at different rates in a fast scanning chip calorimeter to below the glass transition temp., to obtain different structural states before anal. of the cold-crystn. behavior on heating. It was found that heating of fully amorphous PBN at 1000 K/s leads to a similar two-step crystn. process as on cooling the quiescent melt, with LC-formation occurring slightly above Tg and their transformation into crystals at their stability limit close to 200 °C. In-situ polarized-light optical microscopy provided information that the transition of the LC-phase into crystals on slow heating is not connected with a change of the micrometer-scale superstructure, as the recently found Schlieren texture remains unchanged.
    26. 26
      Ding, Q.; Soccio, M.; Lotti, N.; Cavallo, D.; Androsch, R. Melt Crystallization of Poly(Butylene 2,6-Naphthalate). Chinese J. Polym. 2020, 38, 311– 322,  DOI: 10.1007/s10118-020-2354-5
      26
      Melt Crystallization of Poly(butylene 2,6-naphthalate)
      Ding, Qian; Soccio, Michelina; Lotti, Nadia; Cavallo, Dario; Androsch, Rene
      Chinese Journal of Polymer Science (2020), 38 (4), 311-322CODEN: CJPSEG; ISSN:0256-7679. (Springer)
      A review. Poly(butylene 2,6-naphthalate) (PBN) is a crystallizable linear polyester contg. a rigid naphthalene unit and flexible methylene spacer in the chem. repeat unit. Polymeric materials made of PBN exhibit excellent anti-abrasion and low friction properties, superior chem. resistance, and outstanding gas barrier characteristics. Many of the properties rely on the presence of crystals and the formation of a semicryst. morphol. To develop specific crystal structures and morphologies during cooling the melt, precise information about the melt-crystn. process is required. This review article summarizes the current knowledge about the temp.-controlled crystal polymorphism of PBN. At rather low supercooling of the melt, with decreasing crystn. temp., β'- and α-crystals grow directly from the melt and organize in largely different spherulitic superstructures. Formation of α-crystals at high supercooling may also proceed via intermediate formation of a transient monotropic liq. cryst. structure, then yielding a non-spherulitic semicryst. morphol. Crystn. of PBN is rather fast since its suppression requires cooling the melt at a rate higher than 6000 K·s-1. For this reason, investigation of the two-step crystn. process at low temps. requires application of sophisticated exptl. tools. These include temp.-resolved X-ray scattering techniques using fast detectors and synchrotron-based X-rays and fast scanning chip calorimetry. Fast scanning chip calorimetry allows freezing the transient liq.-cryst. structure before its conversion into α-crystals, by fast cooling to below its glass transition temp. Subsequent anal. using polarized-light optical microscopy reveals its texture and X-ray scattering confirms the smectic arrangement of the mesogens. The combination of a large variety of exptl. techniques allows obtaining a complete picture about crystn. of PBN in the entire range of melt-supercoolings down to the glass transition, including quant. data about the crystn. kinetics, semicryst. morphologies at the micrometer length scale, as well as nanoscale X-ray structure information.
    27. 27
      Ding, Q.; Jehnichen, D.; Göbel, M.; Soccio, M.; Lotti, N.; Cavallo, D.; Androsch, R. Smectic Liquid Crystal Schlieren Texture in Rapidly Cooled Poly(Butylene Naphthalate). Eur. Polym. J. 2018, 101, 90– 95,  DOI: 10.1016/j.eurpolymj.2018.02.010
      27
      Smectic liquid crystal Schlieren texture in rapidly cooled poly(butylene naphthalate)
      Ding, Qian; Jehnichen, Dieter; Gobel, Michael; Soccio, Michelina; Lotti, Nadia; Cavallo, Dario; Androsch, Rene
      European Polymer Journal (2018), 101 (), 90-95CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Ltd.)
      The morphol. of partially cryst./ordered poly(butylene naphthalate) (PBN) forming on cooling the melt has been analyzed by polarized-light optical microscopy (POM) and microfocus-beam X-ray diffraction (XRD). Crystn. at rather low supercooling of the melt, at temps. higher than about 200°C, leads to slow and irregular spherulitic growth of β'-crystals, with spherulites not showing a distinct Maltese cross in POM. At temps. between approx. 200 and 160°C, the melt partially converts directly to α-crystals, and the obtained spherulitic superstructure reveals an increasing nuclei d. with decreasing crystn. temp. At even lower temp., a liq. cryst. (LC) phase develops. This mesophase may subsequently convert to α-crystals according to Ostwald's rule of stages. The transition of the LC-phase into α-crystals is suppressed at temps. lower than about 120°C or on cooling faster than about 200-500K/s. X-ray anal. of PBN liq. crystals formed at well-defined cooling conditions in a fast scanning chip calorimeter revealed smectic periodicity while there is simultaneously obsd. a distinct Schlieren texture in POM.
    28. 28
      Cavallo, D.; Mileva, D.; Portale, G.; Zhang, L.; Balzano, L.; Alfonso, G. C.; Androsch, R. Mesophase-Mediated Crystallization of Poly(Butylene-2,6- Naphthalate): An Example of Ostwald’s Rule of Stages. ACS Macro Lett. 2012, 1, 1051– 1055,  DOI: 10.1021/mz300349z
      28
      Mesophase-Mediated Crystallization of Poly(butylene-2,6-naphthalate): An Example of Ostwald's Rule of Stages
      Cavallo, Dario; Mileva, Daniela; Portale, Giuseppe; Zhang, Li; Balzano, Luigi; Alfonso, Giovanni C.; Androsch, Rene
      ACS Macro Letters (2012), 1 (8), 1051-1055CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
      The investigation of poly(butylene-2,6-naphthalate) crystn. by means of chip-calorimetry and ultrafast wide-angle X-ray diffraction (WAXD) revealed the existence of two possible mechanisms. The formation of the stable triclinic α-phase occurs directly from the undercooled melt at low cooling rates/high crystn. temp. At higher cooling rates a two-stage route is obsd.: crystn. was preceded by the formation of a mesomorphic phase from the isotropic melt. The monotropic behavior of poly(butylene-2,6-naphthalate), becoming apparent only under severe cooling conditions, obeys the well-known Ostwald's rule of stages.
    29. 29
      Martin, J.; Davidson, E. C.; Greco, C.; Xu, W.; Bannock, J. H.; Agirre, A.; de Mello, J.; Segalman, R. A.; Stingelin, N.; Daoulas, K. C. Temperature-Dependence of Persistence Length Affects Phenomenological Descriptions of Aligning Interactions in Nematic Semiconducting Polymers. Chem. Mater. 2018, 30, 748– 761,  DOI: 10.1021/acs.chemmater.7b04194
      29
      Temperature-Dependence of Persistence Length Affects Phenomenological Descriptions of Aligning Interactions in Nematic Semiconducting Polymers
      Martin, Jaime; Davidson, Emily C.; Greco, Cristina; Xu, Wenmin; Bannock, James H.; Agirre, Amaia; de Mello, John; Segalman, Rachel A.; Stingelin, Natalie; Daoulas, Kostas Ch.
      Chemistry of Materials (2018), 30 (3), 748-761CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Electronic and optical properties of conjugated polymers are strongly affected by their solid-state microstructure. In nematic polymers, mesoscopic order and structure can be theor. understood using Maier-Saupe (MS) models, motivating us to apply them to conjugated macromol. systems and consider the problem of their material-specific parametrization. MS models represent polymers by worm-like chains (WLC) and can describe collective polymer alignment through anisotropic MS interactions. Their strength is controlled by a phenomenol. temp.-dependent parameter, υ(T). We undertake the challenging task of estg. material-specific υ(T), combining expts. and SCF theory (SCFT). Considering three different materials and a spectrum of mol. wts., we cover the cases of rod-like, semiflexible, and flexible conjugated polymers. The temp. of the isotropic-nematic transition, TIN, is identified via polarized optical microscopy and spectroscopy. The polymers are mapped on WLC with temp.-dependent persistence length. Fixed persistence lengths are also considered, reproducing situations addressed in earlier studies. We est. υ(T) by matching TIN in expts. and SCFT treatment of the MS model. An important conclusion is that accounting explicitly for changes of persistence length with temp. has significant qual. effects on υ(T). We moreover correlate our findings with earlier discussions on the thermodn. nature of phenomenol. MS interactions.
    30. 30
      Kawamura, T.; Misaki, M.; Koshiba, Y.; Horie, S.; Kinashi, K.; Ishida, K.; Ueda, Y. Crystalline Thin Films of β-Phase Poly(9,9-Dioctylfluorene). Thin Solid Films 2011, 519, 2247– 2250,  DOI: 10.1016/j.tsf.2010.10.048
      30
      Crystalline thin films of β-phase poly(9,9-dioctylfluorene)
      Kawamura, Takuji; Misaki, Masahiro; Koshiba, Yasuko; Horie, Satoshi; Kinashi, Kenji; Ishida, Kenji; Ueda, Yasukiyo
      Thin Solid Films (2011), 519 (7), 2247-2250CODEN: THSFAP; ISSN:0040-6090. (Elsevier B.V.)
      The detailed structure of cryst. β-phase poly(9,9-dioctylfluorene) (PFO) films was studied by polarized optical measurements, transmission electron microscopy, and grazing-incidence X-ray diffraction. Cryst. β-phase PFO thin films were fabricated by a friction transfer technique and subsequent vapor treatment. Compared to the α-phase, the lattice parameters of the β-phase crystals shrank along the a-axis (film thickness direction) and elongated along the b-axis (side-chain direction), but the period along the c-axis (main-chain direction) remained nearly equal. These changes in mol. packing were consistent with a planar conformational change from the α-phase to the β-phase of PFO.
    31. 31
      Elshaikh, M.; Marouf, A. A. S.; Modwi, A.; Ibnaouf, K. H. Influence of the Organic Solvents on the α and β Phases of a Conjugated Polymer (PFO). Dig. J. Nanomater. Biostructures 2019, 14, 1069– 1077
      There is no corresponding record for this reference.
    32. 32
      Wang, W.; Fenni, S. E.; Ma, Z.; Righetti, M. C.; Cangialosi, D.; Di Lorenzo, M. L.; Cavallo, D. Glass Transition and Aging of the Rigid Amorphous Fraction in Polymorphic Poly(Butene-1). Polymer 2021, 226, 1– 9,  DOI: 10.1016/j.polymer.2021.123830
      There is no corresponding record for this reference.
    33. 33
      Cangialosi, D.; Alegría, A.; Colmenero, J. Cooling Rate Dependent Glass Transition in Thin Polymer Films and in Bulk. In Fast Scanning Calorimetry , 2016, pp 403– 431.
      There is no corresponding record for this reference.
    34. 34
      Martín, J.; Stingelin, N.; Cangialosi, D. Direct Calorimetric Observation of the Rigid Amorphous Fraction in a Semiconducting Polymer. J. Phys. Chem. Lett. 2018, 9, 990– 995
      34
      Direct Calorimetric Observation of the Rigid Amorphous Fraction in a Semiconducting Polymer
      Martin, Jaime; Stingelin, Natalie; Cangialosi, Daniele
      Journal of Physical Chemistry Letters (2018), 9 (5), 990-995CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      The performance of polymeric semiconductors is profoundly affected by the thermodn. state of its cryst. and amorphous fractions and how they affect the optoelectronic properties. While intense research has been conducted on the cryst. features, fundamental understanding of the amorphous fraction(s) is still lacking. Here, we employ fast scanning calorimetry to provide insights on the glass transition of the archetypal conjugated polymer poly(3-hexylthiophene) (P3HT). According to the conceptual definition of the glass transition temp. (Tg), i.e., the temp. marking the crossover from the melt in metastable equil. to the nonequil. glass, an enthalpy relaxation should be obsd. by calorimetry when the glass is aged below Tg. Thus, we are able to identify the enthalpy relaxations of mobile and rigid amorphous fractions (MAF and RAF, resp.) of P3HT and to det. their resp. Tg. Our work moreover highlights that the RAF should be included in structural models when establishing structure/property interrelationships of polymer semiconductors.
    35. 35
      Lorenzo, A. T.; Arnal, M. L.; Albuerne, J.; Müller, A. J. DSC Isothermal Polymer Crystallization Kinetics Measurements and the Use of the Avrami Equation to Fit the Data: Guidelines to Avoid Common Problems. Polym. Test. 2007, 26, 222– 231,  DOI: 10.1016/j.polymertesting.2006.10.005
      35
      DSC isothermal polymer crystallization kinetics measurements and the use of the Avrami equation to fit the data: Guidelines to avoid common problems
      Lorenzo, Arnaldo T.; Arnal, Maria Luisa; Albuerne, Julio; Mueller, Alejandro J.
      Polymer Testing (2007), 26 (2), 222-231CODEN: POTEDZ; ISSN:0142-9418. (Elsevier B.V.)
      Guidelines were developed to adequately fit isothermal polymer crystn. kinetics data obtained by differential scanning calorimetry (DSC) using the Avrami equation. A methodol. on how the exptl. DSC data should be measured and later analyzed to minimize possible errors assocd. with data manipulation is provided by a thorough evaluation of: (i) detn. of the onset of crystn. or induction time, (ii) the establishment of the baseline and incomplete isothermal crystn. data, (iii) the effect of cooling rate from the melt to isothermal crystn. temp., and (iv) the conversion range used for fitting.
    36. 36
      Pérez-Camargo, R. A.; Liu, G. M.; Wang, D. J.; Müller, A. J. Experimental and Data Fitting Guidelines for the Determination of Polymer Crystallization Kinetics. Chinese J. Polym. Sci. 2022, 40, 658– 691
      36
      Experimental and Data Fitting Guidelines for the Determination of Polymer Crystallization Kinetics
      Perez-Camargo, Ricardo Arpad; Liu, Guo-Ming; Wang, Du-Jin; Muller, Alejandro J.
      Chinese Journal of Polymer Science (2022), 40 (6), 658-691CODEN: CJPSEG; ISSN:0256-7679. (Springer)
      A review. The crystn. kinetics of semicryst. polymers is often studied with isothermal expts. and analyzed by fitting the data with anal. expressions of the Avrami and Lauritzen and Hoffman (LH) theories. To correctly carry out the anal., precautions in both expts. and data fitting should be taken. Here, we systematically discussed the factors that influence the validity of the crystn. kinetics study. The basic concepts and fundamentals of the Avrami and LH theories were introduced at first. Then, exptl. protocols were discussed in detail. To clarify the impact of various exptl. parameters, selected common polymers, i.e., polypropylene and polylactide, were studied using various exptl. techniques (i.e., differential scanning calorimetry and polarized light optical microscopy). Common mistakes were simulated under conditions when non-ideal exptl. parameters were applied. Furthermore, from a practical point of view, we show how to fit the exptl. data to the Avrami and the LH theories, using an Origin App developed by us.
    37. 37
      Müller, A. J.; Balsamo, V.; Arnal, M. L. Nucleation and Crystallization in Diblock and Triblock Copolymers. Adv. Polym. Sci. 2005, 190, 1– 63
      37
      Nucleation and crystallization in diblock and triblock copolymers
      Muller, Alejandro J.; Balsamo, Vittoria; Arnal, Maria Luisa
      Advances in Polymer Science (2005), 190 (Block Copolymers II), 1-63CODEN: APSIDK; ISSN:0065-3195. (Springer GmbH)
      A review. Crystn. of block copolymer microdomains can have a tremendous influence on the morphol., properties and applications of these materials. In this review, particular emphasis is placed on the nucleation, crystn., thermal properties, and morphol. of diblock and triblock copolymers with one or two crystallizable components. The issues of the different types of nucleation processes (i.e., homogeneous nucleation and heterogeneous nucleation by different types of heterogeneities and surface nucleation) and their relation to the crystn. kinetics of the components is addressed in detail in a wide range of polymeric materials for droplet dispersions, blends, and block copolymers. The case of AB double cryst. diblock copolymers is discussed in the light of recent works on biodegradable systems, while the nucleation, crystn. and morphol. of more complex materials like ABC triblock copolymers with one or 2 crystallizable components are thoroughly reviewed.
    38. 38
      Balsamo, V.; Urdaneta, N.; Pérez, L.; Carrizales, P.; Abetz, V.; Müller, A. J. Effect of the Polyethylene Confinement and Topology on Its Crystallisation within Semicrystalline ABC Triblock Copolymers. Eur. Polym. J. 2004, 40, 1033– 1049,  DOI: 10.1016/j.eurpolymj.2004.01.009
      38
      Effect of the polyethylene confinement and topology on its crystallization within semicrystalline ABC triblock copolymers
      Balsamo, V.; Urdaneta, N.; Perez, L.; Carrizales, P.; Abetz, V.; Muller, A. J.
      European Polymer Journal (2004), 40 (6), 1033-1049CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Science B.V.)
      The isothermal crystn. behavior of the polyethylene block within polystyrene-b-polyethylene-b-poly(.vepsiln.-caprolactone), SEC, triblock copolymers was studied by differential scanning calorimetry. The morphol. was obsd. by transmission electron microscopy. Melting scans after isothermal crystn. performed at different times were employed to det. the crystn. kinetics one step at a time ("isothermal step crystn."). Double melting endotherms were obsd. after isothermal crystn. and they were interpreted as a result of the melting of two lamellar populations. These arise from the intrinsic short chain branching distribution within the hydrogenated polybutadiene chains that conform the PE blocks and from their location within the copolymer microdomains. The Hoffman-Weeks procedure failed to yield reasonable values for the equil. m.p. of the PE blocks as a result of the distribution of linear sequences present in these blocks. The results indicate that as the degree of PE confinement increases the Avrami index decreases to values that are even lower than 1, a result that can be explained by the nature of the homogeneous nucleation process that is in between sporadic and instantaneous.

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    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.chemmater.2c02917.

    • PLOM experiments to determine the microscopic morphology of the material as a function of temperature; melting behavior of isothermal crystallized sample monitored by FSC at different Tas from both the ISO state and NEM state; and isothermal crystallization kinetics results from WAXS experiments and FFT analysis of AFM experiments (PDF)


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