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Unraveling the Complex Polymorphic Crystallization Behavior of the Alternating Copolymer DMDS-alt-DVE
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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 Sebastián 20018, Spain
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  • Justine Elgoyhen
    Justine Elgoyhen
    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 Sebastián 20018, Spain
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  • Radmila Tomovska
    Radmila Tomovska
    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 Sebastián 20018, Spain
    IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5, Bilbao 48009, Spain
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    Orcidhttps://orcid.org/0000-0003-1076-7988
  • 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 Sebastián 20018, Spain
    IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5, Bilbao 48009, Spain
    Campus Industrial de Ferrol, CITENI, Esteiro, Universidade da Coruña, Ferrol 15403, Spain
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  • Cuong Minh Quoc Le
    Cuong Minh Quoc Le
    Institut de Sciences des Matériaux de Mulhouse (IS2M), UMR CNRS 7361, Université de Haute-Alsace, 15 rue Jean Starcky, Mulhouse, Cedex 68057, France
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  • Abraham Chemtob
    Abraham Chemtob
    Institut de Sciences des Matériaux de Mulhouse (IS2M), UMR CNRS 7361, Université de Haute-Alsace, 15 rue Jean Starcky, Mulhouse, Cedex 68057, France
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    Orcidhttps://orcid.org/0000-0003-4434-1870
  • Brahim Bessif
    Brahim Bessif
    Institute of Physics, University of Freiburg, Hermann-Herder-Str. 3, Freiburg 79104, Germany
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  • Barbara Heck
    Barbara Heck
    Institute of Physics, University of Freiburg, Hermann-Herder-Str. 3, Freiburg 79104, Germany
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    Orcidhttps://orcid.org/0000-0002-5904-7597
  • Günter Reiter
    Günter Reiter
    Institute of Physics, University of Freiburg, Hermann-Herder-Str. 3, Freiburg 79104, Germany
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    Orcidhttps://orcid.org/0000-0003-4578-8316
  • 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 Sebastián 20018, Spain
    IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5, Bilbao 48009, Spain
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0001-7009-7715
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ACS Applied Polymer Materials

Cite this: ACS Appl. Polym. Mater. 2023, 5, 7, 5260–5269
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https://doi.org/10.1021/acsapm.3c00684
Published June 9, 2023

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Abstract

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A complex crystallization behavior was observed for the alternating copolymer DMDS-alt-DVE synthesized via thiol–ene step-growth polymerization. Understanding the underlying complex crystallization processes of such innovative polythioethers is critical for their application, for example, in polymer coating technologies. These alternating copolymers have polymorphic traits, resulting in different phases that may display distinct crystalline structures. The copolymer DMDS-alt-DVE was studied in an earlier work, where only two crystalline phases were reported: a low melting, L – Tm, and high melting, H – Tm phase. Remarkably, the H – Tm form was only achieved by the previous formation and melting of the L – Tm form. We applied calorimetric techniques encompassing seven orders of magnitude in scanning rates to further explore this complex polymorphic behavior. Most importantly, by rapidly quenching the sample to temperatures well below room temperature, we detected an additional polymorphic form (characterized by a very low melting phase, denoted VL – Tm). Moreover, through tailored thermal protocols, we successfully produced samples containing only one, two, or all three polymorphs, providing insights into their interrelationships. Understanding polymorphism, crystallization, and the resulting morphological differences can have significant implications and potential impact on mechanical resistance and barrier properties.

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Introduction

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Polymerization technologies have recently focused on thiol–ene chemistry. (1−8) Historically, this polymerization approach has been used mainly in bulk or solution for applications such as coatings or surface modification. (2,3,5,7) Aiming to make the process more eco-friendly, there has been a growing interest in thiol–ene polymerization in aqueous dispersed media, such as emulsion and miniemulsion. (4,6,8−11) Le et al. reported the synthesis of polythioethers with high sulfur content. Such polymers have the ability to crystallize, yielding semicrystalline properties (9) which are directly related to their chemical and mechanical resistance. (12) The characterization of newly synthesized materials, mainly when specific applications are targeted such as barrier coatings or materials with high mechanical resistance, requires a comprehensive understanding of their crystallization behavior.
The alternating copolymer DMDS-alt-DVE studied in this work is derived by alternatingly linking monomers of di(ethylene glycol) divinyl ether (DVE) and 2,2′-dimercaptodiethyl sulfide (DMDS). This polythioether exhibits different polymorphic forms. In general, polymorphic materials are substances that can form several distinctly different crystalline phases. (13−15) Polymorphism can profoundly impact the mechanical, thermal, and functional properties of a material, (15−17) and it is a highly researched topic in fields ranging from polymer science to electronics and biology. (18) The crystallization behavior and phase transformations of polymorphic materials are influenced by an extensive array of factors, such as temperature variation, additives, solvents, or nucleating agents. (14,17) A specific crystal form will develop due to an interplay of thermodynamics and kinetics directly related to the processing conditions. For instance, kinetically-controlled solidification may generate metastable structures with high values in free energy, whereas thermodynamically dominated crystallization typically leads to more stable structures. (19) Typically, the nucleation stage decides which phase will form. However, in some cases, a transformation from a metastable to a more stable form may be observed, (17,20) a process often causing complications in industrial applications of these materials.
Materials exhibiting polymorphism are sometimes considered problematic as controlling polymorph formation can be difficult. (16,17) However, in recent years, significant advances in implementing these materials in unprecedented applications have been achieved by exploiting and understanding the behavior of each polymorphic form. (16−19) The discovery of unknown polymorphic forms, with potentially different crystalline structures, and a profound understanding of how they can be achieved and controlled, allow for widening the spectrum of properties relevant to an array of applications. (21) For instance, isotactic poly(1-butene) (iPB) is a polymorphic material that can exist in different crystalline forms; when crystallized from the melt, it forms unstable tetragonal form II crystals. However, upon aging at room temperature, iPB will slowly transform into the more stable hexagonal form I crystals. The transformed crystals are reported to have enhanced elastic properties and a higher melting temperature, which makes i-PB highly sought after for various applications, including tubes, water pipes, and pressurized tanks. (22−26) In addition, isotactic polypropylene (iPP) is known to exhibit a monoclinic α-phase, a trigonal β-phase, and the orthorhombic γ-phase. iPP mainly crystallizes into the more thermodynamically stable α-form when crystallizing from the melt; however, by introducing β-nucleating agents, the β-form is obtained, which is reported to have higher ductility, higher impact resistance, and better weldability than the α-form. (27−30)
In this work, we focus on the tunability of the alternating copolymer DMDS-alt-DVE by investigating the calorimetric behavior of its various polymorphs in depth. By employing experiments spanning seven orders of magnitude in scanning rates, we comprehensively understand the structural transitions within the copolymer. We utilize a microcalorimeter (μ-differential scanning calorimeter, μ-DSC) for low scanning rates, a conventional DSC for intermediate rates, and a fast scanning chip calorimeter (FSC) for very fast rates. The morphology is examined using polarized light optical microscopy (PLOM), while the crystalline structure is analyzed through wide-angle X-ray scattering (WAXS). Our primary focus is to comprehensively understand all possible structural transitions of the DMDS-alt-DVE alternating copolymer and identify reliable thermal protocols that enable the tuning of properties by accessing different combinations of polymorphic phases. This knowledge is essential for maximizing the potential of this copolymer in various applications.

Experimental Section

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Materials

The DMDS-alt-DVE alternating copolymer was synthesized via thiol–ene step-growth polymerization between 2,2′ DMDS and a diene di(ethylene glycol) DVE (Scheme 1).

Scheme 1

Scheme 1. Reaction for the Formation of DMDS-alt-DVE
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The polymer used in this study has a number average molecular weight (Mn) of 9.8 kDa, a weight average molecular weight (Mw) of 21.9 kDa, and a polydispersity (Đ) of 2.23. The synthesis and molecular weight determination are described in the Supporting Information (SI).

μ-DSC

The measurements were conducted using a Setaram micro-DSC (Micro-Calvet) connected to an Intracooler III under a nitrogen atmosphere with 20 mL/min flow. The samples measured weighted ca. 10 mg. Non-isothermal experiments were conducted where the samples were heated and cooled at a rate of 0.2 °C/min (0.0033 °C/s). Samples were heated from 25 °C to a temperature thirty degrees above the melting point (Tm + 30 °C) to ensure erasing thermal history for 3 min, then cooled to a temperature below the glass transition temperature (Tg), and subsequently heated thirty degrees above Tm. The relevant temperatures to consider are the crystallization temperature (Tc), the melting point (Tm), and the glass transition temperature (Tg).

DSC

The experiments were performed using a PerkinElmer DSC 8500 connected to an Intracooler III under a nitrogen atmosphere with 20 mL/min flow. The DSC 8500 was calibrated with indium and tin standards. The samples measured were ca. 5 mg. The Pyris software was used to analyze the data. The samples were heated and cooled at 20 °C/min (0.33 °C/s) during non-isothermal experiments. The sample was heated from room temperature (RT = 25 °C) to a temperature ca. thirty degrees above Tm2 (i.e., 120 °C) for 3 min to completely erase thermal history. The sample was then cooled to a temperature below the glass transition temperature (Tg ≈ −45 °C) and heated again to Tm2 + 30 °C.

FSC

FSC experiments were performed on a Mettler-Toledo Flash DSC 2+ device. The equipment was 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 before 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. It is important to notice that for FSC measurements, the sample mass is in the nanogram scale of magnitude. The STARe software was used to analyze the data. The Results and Discussion section describes the different protocols employed in detail; rates used for this technique ranged from 1 to 10,000 °C/s.

PLOM

Experiments were performed on a polarized light optical microscope, Olympus BX51 (Olympus, Tokyo, Japan), with an Olympus SC50 digital camera coupled to the microscope. The PLOM was equipped with a Linkam-15 TP-91 hot stage Linkam, Tadworth, U.K., connected to a liquid nitrogen cooling system that was used to observe the morphology of the sample. Films of around 50 μm thickness were prepared by melting the sample between two glass slides.

WAXS

Experiments were performed using a D500 X-ray powder diffractometer (Siemens, Germany) in reflection mode (θ–2θ scans) with a Cu-Kα radiation source (λ = 1.54 Å) and a scintillation counter at an angular resolution slightly better than 0.1°. The diffractometer was equipped with an evacuated temperature controlled TTK sample chamber (Paar, Austria). To achieve sub-ambient temperature ranges, the chamber was connected to a liquid nitrogen reservoir. The polymer powder, which scattered isotropically, was deposited on an aluminum plate (fabricated in the lab) and placed on a brass block. The temperature was varied by resistive heating through controlling the current. The temperature was measured by a thermometer at the bottom of the heated brass block. This temperature was calibrated to the sample temperature by measuring the actual temperature at the surface of the polymer samples in a control experiment using an external thermocouple (Mini Dual K/J Thermometer, Uni-T, Munich, Germany). Data points of the XRD patterns obtained from the polymers were collected over a range of the scattering angle between the incident beams and diffracted beam (2θ) from ≈1.8° to 30° at steps (Δ2θ) of 0.04°, each measured for 10 s. Changes in position and intensity of peaks of the diffracted X-rays were measured upon crystallization and melting of the polymers.

Results and Discussion

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Investigating the Crystallization of the H – Tm Form of DMDS-alt-DVE Alternating Copolymer

Based on a combination of techniques such as a PLOM, X-ray scattering, and conventional DSC employing scan rates of 5 °C/min, the crystallization behavior of the alternating copolymer DMDS-alt-DVE was studied recently. (31) The polymorphic nature of this polymer was established, and two different polymorphic forms were identified, having distinctly different melting temperatures (Tm1 and Tm2, respectively). The low-melting temperature polymorph (L – Tm) was reported to have a Tm1 of ca. 68 °C, while the high-melting polymorph (H – Tm) had a Tm2 of ca. 81 °C. A table reporting approximate crystallization and melting temperatures obtained by the different calorimeters and the corresponding scan rates can be found in the Supporting Information (see Table S1).
In the present study, non-isothermal DSC experiments were carried out, employing heating and cooling scan rates of 20 °C/min. The resulting scans presented no detectable differences from those obtained at a slower scan rate of 5 °C/min. (31) The corresponding DSC results of the heating and cooling runs are reported in Figure 1A. During heating, the DMDS-alt-DVE alternating copolymer melted at Tm1 ≈ 66 °C. Following this initial melting, the sample underwent a cold-crystallization step at Tcc ≈ 68 °C, followed by a second melting at Tm2 ≈ 81 °C.

Figure 1

Figure 1. Thermal behavior of the DMDS-alt-DVE alternating copolymer determined via DSC, μ-DSC, and FSC. (A) DSC scans at 20 °C/min; (B) μ-DSC scans at 0.2 °C/min. (C) Thermal protocol employed for isothermal crystallization in FSC. (D) FSC heating scans (“Analysis Scan”) after isothermal crystallization for 24 h at varying Tc. The arrows point to the peaks corresponding to H – Tm, L – Tm, or VL – Tm forms, respectively and the curves correspond to: first heating (black), cooling (blue), and second heating (red).”

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According to the data reported in Figure 1A, the first endotherm (i.e., Tm1) is attributed to the melting of the low-melting temperature polymorph, the L – Tm form. After the L – Tm has melted, the sample re-crystallized at Tcc (in a cold-crystallization process) into the high-melting temperature polymorph, the H – Tm form, which melted at higher temperatures (i.e., at Tm2). Interestingly, when cooling from the molten state, only a single crystallization peak was observed at a crystallization temperature of Tc ≈ 40 °C, indicating that only one of the polymorphs, i.e., the L – Tm form, crystallized during cooling, as demonstrated in our previous work. (31) Thus, by cooling from the molten state at 20 °C/min, only the L – Tm form was generated. The second heating scan in Figure 1A further supports this conclusion, showing similar behavior to that observed during the first heating. Upon heating, the L – Tm phase melted, the sample re-crystallized (cold-crystallization) and transformed into the H – Tm phase, and finally, the H – Tm phase melted. This sequential behavior occurred because the molten L – Tm phase provided a non-equilibrated melt with the memory of the previous ordered state, which assisted nucleation of the H – Tm form. That is, the formation of the H – Tm form was initiated by a kind of self-seeding (31,32) from the memory of the molten L – Tm form. Interestingly, when using a conventional DSC, identical results were obtained for all scanning rates ranging from 1 to 50 °C/min. That is, crystallization of the H – Tm form was not achieved at any of these scanning rates when cooling the sample from the molten state at T > Tm2. (31) Furthermore, our findings are consistent with Ostwald’s rule of stages, which describes the sequential transformation of DMDS-alt-DVE as crystallization progresses. This phenomenon suggests that the first polymorph to crystallize from a polymer melt is the closest in structure to the amorphous state and differs the least in energy, eventually transforming into the more stable form. (33,34)
It is crucial to study the influence of the scanning rate on the formation of the H – Tm form to understand if its direct formation from the melt is impossible even at an extremely slow cooling rate or if the formation of the H – Tm form can also be initiated from the molten state at T > Tm2, for example, by heterogeneous nucleation. In this work, complementary experiments have been performed at rates slower than 1 °C/min. By employing μ-DSC, we performed non-isothermal experiments at a cooling rate of 0.2 °C/min in the same manner as a conventional DSC. The sample was heated for 3 min to a temperature thirty degrees above Tm2, slowly cooled to a temperature below Tg, and subsequently reheated above Tm2.
Figure 1B shows the results of these μ-DSC experiments. The first heating scan did not exhibit any significant differences compared to the results obtained by standard DSC for rates between 1 to 50 °C/min (see also Figure 1A). The lower observed melting peak corresponds to the L – Tm form, and the higher melting peak corresponds to the H – Tm, as indicated by arrows in Figure 1B. During cooling the sample at 0.2 °C/min, a single crystallization peak was observed at a rather high temperature, with an exothermic peak at Tc ≈ 69 °C. Strikingly, this crystallization temperature is higher than Tm1 measured for the L – Tm phase, indicating that this crystallization peak cannot correspond to the crystallization of the L – Tm form. Thus, it can only be due to the crystallization of the H – Tm phase. This conclusion is further supported by the absence of any melting peak associated with the L – Tm during the second μ-DSC heating scan in Figure 1B. A single melting point was observed during the second heating, which coincided with the melting temperature of the H – Tm phase, confirming that the H – Tm form crystallized at ca. 69 °C. The results of Figure 1B indicate that in the μ-DSC experiments, the H – Tm form of the alternating copolymer DMDS-alt-DVE can be obtained through slow cooling (i.e., at 0.2 °C/min) of the molten sample.
In light of these results, a series of experiments were carried out to explore if the H – Tm form can also be achieved by isothermal crystallization. To this end, we used FSC, a technique that allows changing temperatures so rapidly that any crystallization can be excluded during the temperature change. (35−41) For such experiments, we used a rate of 1000 °C/s. At such a cooling rate, we did not detect any crystallization, as will be shown later in the section on the influence of the cooling rate. To erase thermal history, the sample was first heated above the maximum melting point. Next, the sample was rapidly cooled to various values of Tc above the Tm1 of the L – Tm form. At Tc > Tm1, only the H – Tm form can crystallize. At these various values of Tc, the sample was then kept for a long time, i.e., 24 h. Subsequently, the sample was rapidly cooled to a temperature below Tg and heated again above the highest melting temperature of the material. The applied thermal protocol is presented schematically in Figure 1C.
Each of these FSC heating scans (the “Analysis Scan”) after isothermal crystallization at various values of Tc (see Figure 1D) showed a single melting endotherm at Tm>80 °C, which we associated with the melting temperature Tm2 of the H – Tm form. Thus, we have demonstrated that by providing sufficiently long times for crystallization, the H – Tm form of DMDS-alt-DVE can also be obtained via isothermal crystallization.

Morphology of the H – Tm Form of the DMDS-alt-DVE Alternating Copolymer

The morphology and structure of a crystalline phase can be influenced by several factors, including nucleation and growth kinetics and the thermal protocol applied to the sample. As a result, depending on the thermal protocol used, the same crystallographic phase can reveal different morphologies. To generate the H – Tm crystalline phase directly from the melt, an experiment was carried out using PLOM on a thick film of ca. 50 μm. To erase thermal history, the sample was first heated thirty degrees above the maximum Tm and then cooled at 50 °C/min to Tc = 70 °C, where it was allowed to crystallize for ca. 32 h. Interestingly, as shown in Figure 2A, a single large spherulite was obtained within an area of ca. 1 mm2. Such large spherulites require an extremely low nucleation probability, i.e., very few nucleation sites were generated at Tc = 70 °C when cooling the sample from the molten state according to the procedure described above. For comparison, Figure 2B shows the H – Tm form obtained with the help of the melt memory of the previous crystalline state of the L – Tm form for an assisted generation of the H – Tm form. First, the sample was heated to erase thermal history and then cooled at 50 °C/min to Tc = 40 °C for 30 min, where the L – Tm form crystallized. Subsequently, the temperature was increased in order to melt the L – Tm form and to crystallize the H – Tm form at Tc = 70 °C for 30 min, yielding the different morphology shown in Figure 2B. In this case, a large number of very small impinged spherulites were observed. This nucleation density was comparable with the one previously reported for thin films of ca. 100 nm. (31) Due to the melt memory of the molten L – Tm form, a large number density of self-nucleation sites was provided, resulting in a large number of small crystallites of the H – Tm form. Tentatively, we attribute the very few nucleation sites observed when cooling the sample directly from the molten state at T > Tm2 to heterogeneous nuclei with a number proportional to the sample volume. We note that in thin films, upon cooling from the molten state at T > Tm2, we never observed crystallization of the H – Tm form. Assuming that thin and thick films contain the same number of heterogeneous nuclei per unit volume, we expect that, compared to the previous examined thin films, the here studied thick films contain 1000 times more heterogeneous nuclei.

Figure 2

Figure 2. PLOM images of the H – Tm form of the alternating copolymer DMDS-alt-DVE after (A) isothermal crystallization at Tc = 70 °C for ca. 32 h and (B) after self-seeding from the L – Tm form and isothermal crystallization at Tc = 70 °C for 30 min.

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It should be noted that the spherulites have a positive sign as indicated by the colors generated when a lambda plate (i.e., a red-sensitive plate) is inserted at a 45° angle with respect to the polarization direction, as done in the present case. A positive spherulite has a larger refractive index (nr) in the radial direction than in the tangential direction (nt < nr). Most polymers exhibit negative spherulites, but there are a few examples where polymers can display, depending on the crystallization conditions, positive spherulites, like isotactic polypropylene, poly(ethylene terephthalate), and poly(hydroxy butyrate). (42,43) The exact origin of the sign of the spherulite is beyond the scope of the present work, requiring further morphological investigations.

Forming and Characterizing the VL – Tm Form of the DMDS-alt-DVE Alternating Copolymer

To further investigate the influence of the cooling rate on the crystallization behavior of the alternating copolymer DMDS-alt-DVE, FSC experiments were conducted as this technique allows for very fast cooling rates. Noteworthy results were obtained by such non-isothermal crystallization experiments performed at various cooling rates but for a constant heating rate of 1000 °C/s. The samples were initially heated thirty degrees above the maximum Tm to erase any thermal history, then cooled to a temperature below Tg, and heated again to temperatures well above Tm.
Figure 3 shows the FSC heating scans (obtained at a constant heating rate of 1000 °C/s) after cooling the samples at different rates as indicated next to each heating curve. For cooling rates faster than 100 °C/s, no signs of crystallization were detected during cooling, corroborated by the absence of melting peaks in the heating scans. Curves corresponding to cooling rates faster than 100 °C/s only showed a glass transition below ca. −40 °C. Thus, for such fast cooling rates, the material remained amorphous.

Figure 3

Figure 3. Thermal behavior of alternating copolymer DMDS-alt-DVE under non-isothermal conditions via FSC. The arrows indicate the distinct phases found during heating at a constant rate of 1000 °C/s, pointing to the peaks corresponding to the L – Tm and VL – Tm forms, respectively.

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For cooling rates of 10, 5, and 2.5 °C/s, the heating scans of the samples showed a sequence of melting–recrystallization–melting processes. During the second heating scan, two distinct melting peaks, separated by a crystallization peak, were observed. The first melting peak was detected around 25 °C, followed by a crystallization peak around 45 °C and the second melting peak around 69 °C. The latter two peaks coincide approximately with the crystallization and melting of the L – Tm form observed with both DSC and μ-DSC, consistent with a previous study. (31) Outstandingly, an additional polymorphic form could be observed that is distinct from the already identified H – Tm and L – Tm forms. The endotherm at Tm, VL ≈ 25 °C does not correspond to any previously reported phase, suggesting the existence of a third polymorphic form for the alternating copolymer DMDS-alt-DVE. When cooling at rates faster than 1 °C/s and slower than 100 °C/s, the newly discovered very low-temperature form melts and re-crystallizes into the L – Tm form, which subsequently melts. We refer to this additional phase as the very low melting temperature form (VL – Tm form or crystalline VL – Tm phase). For a cooling rate of 1 °C/s, the peak at Tm, VL ≈ 25 °C became smaller, and the one at Tm1 ≈ 69 °C became more prominent. This behavior is consistent with the results shown above, for example, in Figure 1B. Microcalorimetry results indicated a tiny peak at Tm ≈ 20 °C, suggesting that a very small amount of the VL – Tm form was generated during slow cooling.
After identifying this additional polymorphic phase (VL – Tm form), experiments were conducted to generate each of the three phases individually and to explore whether they can co-exist. To generate each phase individually, the samples were initially heated well above the maximum Tm to erase any thermal history (e.g., to 170 °C).
To avoid crystallization during cooling, samples were then rapidly cooled to different Tc values, where they were allowed to isothermally crystallize for 1 h. Finally, the samples were rapidly cooled below Tg. For each Tc, the subsequent FSC heating scan, denoted as “Analysis Scan” in Figure 4A, revealed the melting of the crystals formed during the 1 h crystallization at Tc. We have chosen heating and cooling rates of 4000 °C/s for the thermal protocol of Figure 4A.

Figure 4

Figure 4. (A) Thermal protocol for isothermal crystallization experiments employed at varying Tc. (B) FSC heating scans at a heating rate of 4000 °C/s, after 1 h isothermal crystallization at the indicated values of Tc. The brackets point to the range of temperatures corresponding to the H – Tm, L – Tm, or VL – Tm forms, respectively.

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Figure 4B shows the FSC heating curves measured after 1 h isothermal crystallization at the values of Tc indicated next to each curve. At Tc = −50 °C, the sample was below Tg; no crystallization occurred. Upon heating at 4000 °C/s, only the glass transition was observed at approximately −37 °C. For a Tc range from −20 to −10 °C, a broad melting endotherm around Tm, VL ≈ 25 °C could be observed. For a Tc range from 20 to 30 °C, another endotherm with a higher melting point of Tm1 ≈ 68 °C was found. The peak at around 25 °C corresponds to the melting of VL – Tm crystals, and that at about 68 °C corresponds to the melting of L – Tm crystals as these values align well with previously found ones. Finally, for Tc = 10 °C, we could observe the convolution of two endotherms; hence, both VL – Tm and L – Tm polymorphs crystallized at that temperature. Interestingly, at a first glance on Figure 4B, no significant endotherms could be detected after isothermal crystallization at Tc = 70 °C. However, if the curve was magnified, a weak endotherm could be observed with a melting point of around 81 °C, associated with melting of crystals of the H – Tm form.
To summarize, the individual generation of each of the phases was accomplished. Through isothermal crystallization at appropriate values of Tc, samples with only one or two crystalline forms can be produced. Individual generation of the VL – Tm form and the L – Tm form can be mainly achieved by isothermal crystallization after rapidly cooling the sample (e.g., at rates faster than 100 °C/s) to a very low Tc. Exclusive generation of the H – Tm form can be achieved either by slow cooling from the melt or by isothermal crystallization over long periods at Tc > Tm1.
Having accomplished the generation of each phase individually by employing the protocols described above, we shift the focus to observing all three distinct forms simultaneously within the same sample. The ability of the material to adopt different crystalline structures under various thermal conditions, potentially leading to different properties, is of interest for tailoring the material properties required for specific applications. For this particular purpose, we devised a complex thermal protocol. However, it is worth noting that there are multiple alternative protocols suitable for accomplishing three distinct forms simultaneously within a sample. Nonetheless, the protocol described here is illustrative of the tunable thermal properties of this alternating copolymer.
In the protocol outlined in Figure 5A, depending on the desired outcome, the indicated crystallization temperatures can be adjusted. To achieve all forms within the same sample, the key requirement is that the highest melting phase (H – Tm) has to be formed first. In the following, the form with an intermediate melting temperature (L – Tm) and finally the one with the lowest melting temperature (VL – Tm) can be generated. For the employed thermal protocol, we have chosen 1000 °C/s for all heating and cooling rates. Following the protocol of Figure 5A, the sample was first heated thirty degrees above the maximum Tm to erase thermal history, then rapidly cooled (at 1000 °C/s) to Tc = 25 °C, and kept at that temperature for 30 min. During this isothermal crystallization step, we generated the L – Tm form. The sample was then rapidly heated to Tc= 70 °C where it was kept for 30 min, and part of the sample was crystallized in the H – Tm form. The L – Tm crystals formed in the previous step melted during heating, but the memory of the previous crystalline state assisted generation of the H – Tm form at Tc= 70 °C. To re-generate the L – Tm form, the sample was rapidly cooled to Tc = 25 °C and kept there for 30 min. After this stage, both the H – Tm and L – Tm have been formed within the same sample. However, the sample was not yet crystallized completely, and crystallization of the VL – Tm form was achieved by rapidly cooling to Tc= −10 °C and keeping the sample at this low isothermal crystallization temperature for 30 min. Finally, the sample was rapidly quenched (at 1000 °C/s) below Tg. After all three forms were generated in the same sample, an FSC heating scan (denoted as “Analysis Scan”, in Figure 5A) was performed to determine the individual melting temperatures.

Figure 5

Figure 5. FSC experiments on alternating copolymer DMDS-alt-DVE. (A) Thermal protocol employed to achieve all three polymorphs of this alternating copolymer within the same sample. (B) FSC results obtained during the analysis (heating) scan shown in the protocol described in (A). All heating and cooling rates for this experiment were 1000 °C/s. The arrows point to the endothermic peaks corresponding to melting of the VL – Tm, L – Tm, and H – Tm forms, respectively.

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Figure 5B shows the corresponding FSC analysis scan performed at a rate of 1000 °C/s, where three melting peaks can be observed. The peak at Tm,VL ≈ 20 °C corresponds to the melting of the VL – Tm form, the peak at Tm1 ≈ 65 °C corresponds to the melting of the L – Tm form, and finally the peak at Tm2 ≈ 95 °C corresponds to the melting of the H – Tm form. We note that due to the fast heating scan, the values of the melting peaks are somewhat higher than those observed for slow heating rates. We conclude that by applying properly-tailored thermal protocols, we can generate each phase individually or produce a sample where two or all three of them co-exist.

Crystalline Structures of the Alternating Copolymer DMDS-alt-DVE at Various Low Temperatures and Related Changes in Time

Our WAXS experiments aimed to explore differences in crystalline structures between the VL – Tm and L – Tm forms. The scattering patterns for the L – Tm and H – Tm forms have been reported previously. (31) Samples were prepared as described in the experimental section. First, thermal history was erased by heating the sample to 100 °C for 1 min, which is above the maximum Tm2. Subsequently, the sample was quenched by rapidly depositing it onto a brass block cooled to −20 °C, where it was kept for 5 min. According to the FSC results discussed above, the VL – Tm form was generated by this thermal treatment. To identify the anticipated crystalline structures, the sample was mounted in the diffractometer’s holder, which had been previously cooled to −10 °C. Starting at this low temperature, ten isothermal WAXS spectra were measured in steps of 5 °C up to 35 °C. Two of these spectra are shown in Figure 6A. The sample was eventually cooled back to room temperature (RT = 20 °C) and measured again after being kept at RT for 4 days. As shown in Figure 6A, the spectrum measured at 20 °C did not differ from the one measured before at 35 °C, indicating the stability of the underlying crystalline L – Tm phase. Notably, at temperatures below ca. 5 °C, the measured spectra showed clear differences from the ones observed at temperatures above ca. 5 °C. As an example, we show in Figure 6A the spectrum measured at −5 °C. In particular, the position of the dominant peak differed by about (0.2 ± 0.05)°, and the peak at ca. 25° was not observed at temperatures below ca. 5 °C. We conclude that the VL – Tm form generated at −20 °C has transformed into the L – Tm form at temperatures above 5 °C.

Figure 6

Figure 6. Isothermal WAXS diffractograms measured at (A) −5 °C (green curve) and 35 °C (black curve) by increasing the temperature in steps of 5 °C after being stored for four days at RT = 20 °C (red curve) and at 90 °C, (amorphous background, blue curve) and (B) −10 °C (black curve) in steps of 5 °C up to 5 °C and left for four days (after 30 min = red curve; 24 h = purple curve; 96 h = green curve) and after heating it to 20 °C (blue curve).

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In order to explore if this transformation was a rapid or a slow process, we examined the temporal evolution of the spectrum measured at 5 °C. As can be seen in Figure 6B, the transformation of the VL – Tm form into the L – Tm form was slow and required more than ca. 30 h. Besides the progressive shifting of the dominant peak to lower scattering angles, two distinguishable peaks emerged out of the initially “broad” peak located at around 23.5°. We tentatively conclude that the VL – Tm form is probably metastable and contains less perfectly ordered crystalline structures. While the similarities of the peak positions may indicate similar unit cell parameters, the difference in the scattering intensities may result from differences in chain packing. For the VL – Tm form, which has the lowest melting temperature, we may expect a rather imperfect or less ordered structure. However, at present, all details of the crystalline structure of the three detected polymorphs are still not resolved.

Conclusions

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This work explored the different polymorphic forms generated by the alternating copolymer DMDS-alt-DVE at low temperatures. We demonstrated that under specific thermal protocols, this polymer has the ability to crystallize into up to three polymorphic forms. Besides the previously presented L – Tm and H – Tm forms, (31) the alternating copolymer DMDS-alt-DVE possesses an additional polymorphic form that can be generated at temperatures well below room temperature (i.e., the VL – Tm polymorph). Due to clear differences in their melting temperatures and certain microstructural features, these polymorphs are easily distinguishable.
Interestingly, as shown here, the most stable crystallographic form (the H – Tm form) of DMDS-alt-DVE can also be established directly from the molten state. Given that there exist appropriate heterogeneous nuclei, the H – Tm form can be generated by either cooling the sample very slowly from the melt (e.g., at a rate of 0.2 °C/min or less) or by cooling the sample rapidly to a temperature above the melting temperature of the L – Tm form and keeping it there for long times (e.g., 24 h or longer). However, even without any heterogeneous nuclei, the H – Tm form can be generated rapidly by first preparing the L – Tm form and employing the melt memory of the previous crystalline state of the L – Tm form for an assisted nucleation of the H – Tm form.
Finally, based on the knowledge of the melting temperatures of the different polymorphs and the corresponding nucleation probability, including concepts of melt memory and self-nucleation, we have successfully devised an appropriate thermal protocol, which allows to generate samples that contain only one, two, or all three crystalline forms. Thus, our results demonstrate the tunability and controlled formation of different crystalline polymorphs with potentially different properties within a single polymer sample. Further studies on each polymorph generated individually may reveal differences in mechanical or optical properties, opening a promising avenue for the exploitation of the specific properties of each polymorph.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsapm.3c00684.

  • A brief description of the synthesis of the alternating copolymer DMDS-alt-DVE, a brief description on the obtention of the molecular weight distribution, and a table containing calorimetric data of DMDS-alt-DVE obtained for different techniques and rates (PDF)

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Author Information

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  • Corresponding Author
    • 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 Sebastián 20018, Spain;  IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5, Bilbao 48009, Spain;  Orcidhttps://orcid.org/0000-0001-7009-7715;  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 Sebastián 20018, Spain
    • Justine Elgoyhen - 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 Sebastián 20018, Spain
    • Radmila Tomovska - 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 Sebastián 20018, Spain;  IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5, Bilbao 48009, Spain;  Orcidhttps://orcid.org/0000-0003-1076-7988
    • 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 Sebastián 20018, Spain;  IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5, Bilbao 48009, Spain;  Campus Industrial de Ferrol, CITENI, Esteiro, Universidade da Coruña, Ferrol 15403, Spain
    • Cuong Minh Quoc Le - Institut de Sciences des Matériaux de Mulhouse (IS2M), UMR CNRS 7361, Université de Haute-Alsace, 15 rue Jean Starcky, Mulhouse, Cedex 68057, France
    • Abraham Chemtob - Institut de Sciences des Matériaux de Mulhouse (IS2M), UMR CNRS 7361, Université de Haute-Alsace, 15 rue Jean Starcky, Mulhouse, Cedex 68057, France;  Orcidhttps://orcid.org/0000-0003-4434-1870
    • Brahim Bessif - Institute of Physics, University of Freiburg, Hermann-Herder-Str. 3, Freiburg 79104, Germany
    • Barbara Heck - Institute of Physics, University of Freiburg, Hermann-Herder-Str. 3, Freiburg 79104, Germany;  Orcidhttps://orcid.org/0000-0002-5904-7597
    • Günter Reiter - Institute of Physics, University of Freiburg, Hermann-Herder-Str. 3, Freiburg 79104, Germany;  Orcidhttps://orcid.org/0000-0003-4578-8316
  • Author Contributions

    The manuscript was written through the contributions of all authors. All authors have approved the final version of the manuscript.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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We acknowledge the support of the Basque Government through grant IT1503-22 and IT-1525-22. J.M thanks 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.

References

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    A review. The controlling factor and mechanism of the crystn. of polymorphs were investigated in various systems; i.e. amino acids, inorg. compds. (calcium carbonate), pharmaceuticals and inclusion compds. The controlling factor depends on the systems (compds. and solvents and additives) and the crystn. methods (cooling crystn., reactive crystn. and anti-solvent crystn.). The controlling factors for each system were found and a schematic diagram was shown. The mechanism of each controlling factor was investigated and some rules were found. It appears that the establishment of "Ostwald's step rule" depends on the systems. In the cooling crystn. of amino acids (L-glutamic acid and L-histidine), the "Ostwald's step rule" cannot be obsd.; however, in the crystn. of BPT esters, it is clearly established. The difference of the temp. effect between L-glutamic acid and L-histidine polymorphs may be related to the difference of the mol. conformation between the polymorphs. In the reactive crystn. of calcium carbonate polymorphs, the concn. (supersatn.) of reactant solns., the mixing rate of the solns., pH, stirring rate and temp. were found to be the controlling factors for the morphol. and the crystn. behavior of polymorphs. As for the effect of additives it should be noted that the additive affects not only one polymorph, but each polymorph. Then, knowing the relative effect of additives on each polymorph is important for the control. The growth kinetics of polymorphs of L-glutamic acid and the mechanism of morphol. change of each polymorph were examd. in the presence of L-phenylalanine (as an additive) with batch crystn. and the single crystal method. The growth rate model including the additive concn. was proposed for each polymorph and the method of the selective crystn. of the polymorphs by controlling the supersatn. and the additive concn. was also indicated. In anti-solvent crystn. of pharmaceuticals (BPT) it was shown that the addn. rate of anti-solvent, initial concn. of solute and temp. are the controlling factors. With the increase of the addn. rate the water compn. in the nucleation zone increases, resulting in the preferential crystn. of the hydrate crystals. The transformation from BH to A form was obsd., however, the transformation rate increased with a decrease in the water addn. rate. Even when none of the A form was detected by XRD a small amt. of fine crystals (A form) is included within the BH crystals and act as seed crystals for the transformation. Furthermore, the change in the mol. structure is related to a dynamic change of the polymorphic crystn. behavior as obsd. in L-Glu and L-His systems. The dependence of the polymorphic crystn. behavior on the mol. structure was systematically investigated using the newly synthesized BPT esters. It appeared that the conformational flexibility, the size of alkyl group of the esters and the presence of functional group influences the formation of hydrogen bond and the polymorphism. The solvent effect on the polymorphism was also examd. in relation to the mol. structure. The functionality of clathrate crystals and the sepn. efficiency of isomers by clathrate crystals depend on their polymorphic crystn. behavior. The mechanism of the mol. recognition for the guest isomers by the host mol. is clarified. It was also elucidated that the release process of a guest biocide mol. from clathrate crystals includes polymorphic transformation.
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    De Rosa, C.; Auriemma, F.; Malafronte, A.; Scoti, M. Crystal Structures and Polymorphism of Polymers: Influence of Defects and Disorder. Polym. Cryst. 2018, 1, e10015  DOI: 10.1002/pcr2.10015
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    Gentili, D.; Gazzano, M.; Melucci, M.; Jones, D.; Cavallini, M. Polymorphism as an Additional Functionality of Materials for Technological Applications at Surfaces and Interfaces. Chem. Soc. Rev. 2019, 48, 2502– 2517,  DOI: 10.1039/C8CS00283E
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    Polymorphism as an additional functionality of materials for technological applications at surfaces and interfaces
    Gentili, Denis; Gazzano, Massimo; Melucci, Manuela; Jones, Derek; Cavallini, Massimiliano
    Chemical Society Reviews (2019), 48 (9), 2502-2517CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    Polymorphism is a widespread phenomenon occurring in many solid materials having important effects in many scientific disciplines. Since mol. packing can det. the functional properties of materials but is often difficult to control, polymorphism has usually been considered a drawback for technol. applications. Thanks to advances in its control over the past few years, polymorphism is now often considered more as an opportunity because it allows a much wider range of functionality in, for example, a solid mol. material, where a corresponding packing type can be selected or even promoted. This tutorial review introduces the reader to the most representative progress in applications of polymorphism as an addnl. functionality of materials esp. in its current promise for technol. applications. In addn., it examines the most powerful strategies to control and fully exploit the intrinsic properties of polymorphism and transitions between its various metastable states, through fine-tuning of mol. packing in a reproducible manner. The aim is to create awareness about polymorphism as a novel enabling technol. rather than as a problem.
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    De Rosa, C.; Scoti, M.; Di Girolamo, R.; de Ballesteros, O. R.; Auriemma, F.; Malafronte, A. Polymorphism in Polymers: A Tool to Tailor Material’s Properties. Polym. Cryst. 2020, 3, 1– 29,  DOI: 10.1002/PCR2.10101
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    Brittain, H. G. Polymorphism in Pharmaceutical Solids, 2nd edition; Brittain, H. G., Ed.; CRC Press: Milford, 2009; vol 192.
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    Liu, C.; Brandenburg, J. G.; Valsson, O.; Kremer, K.; Bereau, T. Free-Energy Landscape of Polymer-Crystal Polymorphism. Soft Matter 2020, 16, 9683– 9692,  DOI: 10.1039/D0SM01342K
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    Free-energy landscape of polymer-crystal polymorphism
    Liu, Chan; Brandenburg, Jan Gerit; Valsson, Omar; Kremer, Kurt; Bereau, Tristan
    Soft Matter (2020), 16 (42), 9683-9692CODEN: SMOABF; ISSN:1744-6848. (Royal Society of Chemistry)
    Polymorphism rationalizes how processing can control the final structure of a material. The rugged free-energy landscape and exceedingly slow kinetics in the solid state have so far hampered computational investigations. We report for the first time the free-energy landscape of a polymorphic cryst. polymer, syndiotactic polystyrene. Coarse-grained metadynamics simulations allow us to efficiently sample the landscape at large. The free-energy difference between the two main polymorphs, α and β, is further investigated by quantum-chem. calcns. The results of the two methods are in line with exptl. observations: they predict β as the more stable polymorph under std. conditions. Critically, the free-energy landscape suggests how the α polymorph may lead to exptl. obsd. kinetic traps. The combination of multiscale modeling, enhanced sampling, and quantum-chem. calcns. offers an appealing strategy to uncover complex free-energy landscapes with polymorphic behavior.
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    Keller, A.; Cheng, S. Z. D. The Role of Metastability in Polymer Phase Transitions. Polymer 1998, 39, 4461– 4487,  DOI: 10.1016/S0032-3861(97)10320-2
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    Zheng, Y.; Pan, P. Crystallization of Biodegradable and Biobased Polyesters: Polymorphism, Cocrystallization, and Structure-Property Relationship. Prog. Polym. Sci. 2020, 109, 101291  DOI: 10.1016/J.PROGPOLYMSCI.2020.101291
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    Crystallization of biodegradable and biobased polyesters: Polymorphism, cocrystallization, and structure-property relationship
    Zheng, Ying; Pan, Pengju
    Progress in Polymer Science (2020), 109 (), 101291CODEN: PRPSB8; ISSN:0079-6700. (Elsevier Ltd.)
    In the past two decades, synthetic biodegradable and biobased polyesters have emerged as a sustainable alternative to traditional petroleum-derived polymers for diverse range of applications. Most of the synthetic biodegradable and biobased polyesters are semicryst. Some of these polymers can exist in a variety of polymorphs depending on the crystn. and processing conditions. In addn., blends or copolymers can exhibit cocrystn. behavior (such as stereocomplex, isomorphic, and isodimorphic crystn.). Polymorphic crystn. and cocrystn. of polymers plays an essential role not only in the scientific understanding of condensed matter structures of polymers, but also in the technol. development and application of this new class of materials. This paper reviews the recent progress in the understanding of the polymorphic crystn., co-crystn., and structure-property relationship of synthetic biodegradable and biobased polyesters that has occurred within the past decade. Particular focus is on the structure, morphol., formation kinetics, and phase transition of crystals grown from biodegradable and biobased polyesters. Since the phys. properties of polymers depend on their crystal structure and morphol., we also reviewed the relationships between the crystn. and processing conditions, cryst. structure and morphol., and phys. properties (e.g., mech. and biodegradability) of biodegradable and biobased polymorphic, cocrystallizable polyesters.
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    Wu, X.; Shi, S.; Yu, Z.; Russell, T. P.; Wang, D. AFM Nanomechanical Mapping and Nanothermal Analysis Reveal Enhanced Crystallization at the Surface of a Semicrystalline Polymer. Polymer 2018, 146, 188– 195,  DOI: 10.1016/J.POLYMER.2018.05.043
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    AFM nanomechanical mapping and nanothermal analysis reveal enhanced crystallization at the surface of a semicrystalline polymer
    Wu, Xuefei; Shi, Shaowei; Yu, Zhongzhen; Russell, Thomas P.; Wang, Dong
    Polymer (2018), 146 (), 188-195CODEN: POLMAG; ISSN:0032-3861. (Elsevier Ltd.)
    We used at. force microscopy (AFM) nanomech. mapping to image the surface of a semicryst. polymer, specifically polymorphic isotactic poly (1-butene) (iPB), to det. the mech. properties of a surface layer, and compared this to the properties in the bulk. The measured Young's modulus of the surface layer as a function of annealing time at room temp. was found to be higher than that of the bulk, indicating a more rapid transformation from form II to I polymorphs and an enhanced movement of polymer chain segments at the surface relative to the bulk for this polymer. Plate-like crystals were found at the surface and, as the annealing temp. increased from 70 to 110 °C, evidence of a surface layer was found that increased in thickness from ∼30 to ∼130 nm, resp. After removing this layer, the morphol. found in the bulk was markedly different. We also used AFM nanothermal anal. to det. the local m.p. (Tm) and found, that the m.p., Tm, of the crystals at the surface was higher than that of the bulk, in keeping with the modulus measurements. The nanomech. and nanothermal properties and the morphol. at the surface suggest an enhanced movement of polymer chain segments at the surface and therefore, an enhanced crystn. at the surface.
  23. 23
    Marigo, A.; Marega, C.; Cecchin, G.; Collina, G.; Ferrara, G. Phase Transition II → I in Isotactic Poly-1-Butene: Wide- and Small-Angle X-Ray Scattering Measurements. Eur. Polym. J. 2000, 36, 131– 136,  DOI: 10.1016/S0014-3057(99)00043-9
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    Phase transition II → I in isotactic poly-1-butene: wide- and small-angle X-ray scattering measurements
    Marigo, Antonio; Marega, Carla; Cecchin, Giuliano; Collina, Gianni; Ferrara, Giuseppe
    European Polymer Journal (1999), 36 (1), 131-136CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Science Ltd.)
    Phase transition II → I in isotactic poly-1-butene was studied by wide- and small-angle X-ray scattering in order to follow the change of crystallinity and of the characteristic parameters of the lamellar stacks over time. Small-angle X-ray scattering exptl. patterns were analyzed by a fitting method with the profiles calcd. from some theor. distribution models of the lamellar thickness. The math. evaluation of small-angle X-ray scattering patterns provided crystallinity values which were compared with those obtained by wide-angle X-ray scattering, in order to obtain information on the lamellar stacks organization. The transition nucleation seems to be localized on lamellar distortion points and the transition itself involves the rearrangement of lamellae and of lamellar stacks.
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    Azzurri, F.; Flores, A.; Alfonso, G. C.; Baltá Calleja, F. J. Polymorphism of Isotactic Poly(1-Butene) as Revealed by Microindentation Hardness. 1: Kinetics of the Transformation. Macromolecules 2002, 35, 9069– 9073,  DOI: 10.1021/ma021005e
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    Polymorphism of isotactic poly(1-butene) as revealed by microindentation hardness. 1. Kinetics of the transformation
    Azzurri, F.; Flores, A.; Alfonso, G. C.; Balta Calleja, F. J.
    Macromolecules (2002), 35 (24), 9069-9073CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    The microindentation hardness technique has been employed to examine the II → I polymorphic transformation of isotactic poly-1-butene taking place upon aging at room temp. The hardness values of form I are shown to be remarkably higher than those of form II due to the denser packing of chains in the hexagonal crystal modification. The kinetics of the II → I transformation has been followed by means of microindentation hardness measurements in real time. The influence of molar mass and crystn. temp. on the kinetics of the polymorphic transformation is examd. Results suggest that the rate of polymorphic transformation is independent of mol. wt. In addn., it is seen that increasing the crystn. temp. (up to 105 °C) notably reduces the time required for a full transformation of form II into form I. The influence of the fraction of amorphous material on the rate of polymorphic transformation is discussed.
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    Cavallo, D.; Kanters, M. J. W.; Caelers, H. J. M.; Portale, G.; Govaert, L. E. Kinetics of the Polymorphic Transition in Isotactic Poly(1-Butene) under Uniaxial Extension. New Insights from Designed Mechanical Histories. Macromolecules 2014, 47, 3033– 3040,  DOI: 10.1021/ma500281f
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    25
    Kinetics of the Polymorphic Transition in Isotactic Poly(1-butene) under Uniaxial Extension. New Insights From Designed Mechanical histories.
    Cavallo, Dario; Kanters, Marc J. W.; Caelers, Harm J. M.; Portale, Giuseppe; Govaert, Leon E.
    Macromolecules (Washington, DC, United States) (2014), 47 (9), 3033-3040CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Isotactic poly(1-butene) (i-PBu) crystallizes upon cooling from the melt in a metastable tetragonal structure (form II), which slowly evolves toward the state of ultimate stability, i.e., the trigonal form I. It is well-known that this polymorphic transformation, which typically requires few weeks at room temp., can be greatly accelerated by the application of mech. stresses and/or deformation. However, the exact mechanism of this kinetics enhancement is not completely understood. In this work, the polymorphic transformation of i-PBu under tensile deformation is investigated in details. Thanks to properly designed mech. histories-including expts. at different true strain and true stress rates-and to in situ wide-angle X-ray diffraction expts., the role of the various deformation parameters is elucidated. The use of different time scales during the expts. enabled us to gain kinetics data on the transition, information which is disregarded in current literature. The set of expts. performed permit to highlight a stress-driven mechanism, active up to a fraction of transformed form I of about 0.4-0.5. After this value is reached, the stress-transformation time superposition principle does not hold anymore and the transition kinetics slows down, since a major part of the total applied stress is carried by the mech. stronger form I lamellae.
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    Qiao, Y.; Wang, Q.; Men, Y. Kinetics of Nucleation and Growth of Form II to I Polymorphic Transition in Polybutene-1 as Revealed by Stepwise Annealing. Macromolecules 2016, 49, 5126– 5136,  DOI: 10.1021/acs.macromol.6b00862
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    26
    Kinetics of Nucleation and Growth of Form II to I Polymorphic Transition in Polybutene-1 as Revealed by Stepwise Annealing
    Qiao, Yongna; Wang, Qiao; Men, Yongfeng
    Macromolecules (Washington, DC, United States) (2016), 49 (14), 5126-5136CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Kinetics of II to I polymorphic transformation in isotactic polybutene-1 (PB-1) and its annealing temp. and time dependencies have been investigated by means of differential scanning calorimetry and in situ wide-angle X-ray diffraction techniques. The PB-1 samples were isothermally crystd. into metastable form II cryst. modification followed by annealing at a lower temp. (Tl) and at a higher temp. (Th) subsequently or at a single temp. (Ts) to promote polymorphic transition from form II to I. This solid-to-solid phase transition was shown to be a two-step process including nucleation and growth suggested by the result that more form I was obtained after being annealed at Tl and Th than annealed at Ts for the same period. Annealing at Tl benefits nucleation due to internal stress induced by unbalanced shrinkage of amorphous and cryst. phases because of their different thermal expansion coeffs., while annealing at Th is beneficial to growth owing to rapid segmental diffusion at that temp. At a given annealing time at Tl (tl) and at Th (th), and fixing one of temps. between Tl and Th, it shows a max. in the transformation-temp. profile that can be correlated with the optimal temp. for nucleation or growth. The phase transition was efficiently accelerated with the increase of isothermal crystn. temp. Such dependency can be understood as a result of higher internal stress built up during cooling from higher isothermal crystn. temp. to Tl. Our results decompd. the polymorphic transition into nucleation and growth for the first time providing a simple and effective way for rapid transition of form II to I in PB-1.
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    Xiao, W.; Wu, P.; Feng, J.; Yao, R. Influence of a Novel β-Nucleating Agent on the Structure, Morphology, and Nonisothermal Crystallization Behavior of Isotactic Polypropylene. J. Appl. Polym. Sci. 2009, 111, 1076– 1085,  DOI: 10.1002/APP.29139
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    Influence of a novel β-nucleating agent on the structure, morphology, and nonisothermal crystallization behavior of isotactic polypropylene
    Xiao, Wenchang; Wu, Peiyi; Feng, Jiachun; Yao, Riyuan
    Journal of Applied Polymer Science (2009), 111 (2), 1076-1085CODEN: JAPNAB; ISSN:0021-8995. (John Wiley & Sons, Inc.)
    The cryst. structure, morphol., and nonisothermal crystn. behavior of isotactic polypropylene (iPP) with and without a novel rare earth-contg. β-nucleating agent (WBG) were investigated with wide-angle X-ray diffraction, polar optical microscopy, and differential scanning calorimetry. WBG could induce the formation of the β form, and a higher proportion of the β form could be obtained by the combined effect of the optimum WBG concn. and a lower cooling rate. The content of the β form could reach more than 0.90 in a 0.08% WBG nucleated sample at cooling rates lower than 5°/min. Polar optical microscopy showed that WBG led to substantial changes in both the morphol. development and crystn. process of iPP. At all the studied cooling rates, the temp. at which the max. rate of crystn. occurred was increased by 8-11° in the presence of the nucleating agent. An anal. of the nonisothermal crystn. kinetics also revealed that the introduction of WBG significantly shortened both the apparent incubation period for crystn. and the overall crystn. time.
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    Marco, C.; Gómez, M. A.; Ellis, G.; Arribas, J. M. Activity of a β-Nucleating Agent for Isotactic Polypropylene and Its Influence on Polymorphic Transitions. J. Appl. Polym. Sci. 2002, 86, 531– 539,  DOI: 10.1002/APP.10811
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    Activity of β-nucleating agent for isotactic polypropylene and its influence on polymorphic transitions
    Marco, C.; Gomez, M. A.; Ellis, G.; Arribas, J. M.
    Journal of Applied Polymer Science (2002), 86 (3), 531-539CODEN: JAPNAB; ISSN:0021-8995. (John Wiley & Sons, Inc.)
    The influence of a nonpigmenting β-nucleating additive in the crystn. of isotactic polypropylene (iPP) is investigated by differential scanning calorimetry and X-ray diffraction. This additive induces the formation of a very high level of the trigonal modification of iPP. The crystn. and melting behavior of the nucleated systems are studied as a function of the cooling and heating rates and the control of the final temp. during the cooling process. The nucleating agent exerts an important effect on the crystn. temps. and the polymorphic transitions of iPP, delaying the β-α recrystn. process through an increase in the stability of the trigonal crystals.
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    Garbarczyk, J.; Paukszta, D.; Borysiak, S. Polymorphism of Isotactic Polypropylene in Presence of Additives, in Blends and in Composites. J. Macromol. Sci. Phys. B 2002, 41, 1267– 1278,  DOI: 10.1081/MB-120013096
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    Horváth, Z.; Sajó, I. E.; Stoll, K.; Menyhárd, A.; Varga, J. The Effect of Molecular Mass on the Polymorphism and Crystalline Structure of Isotactic Polypropylene. Express Polym. Lett. 2010, 4, 101– 114,  DOI: 10.3144/EXPRESSPOLYMLETT.2010.15
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    The effect of molecular mass on the polymorphism and crystalline structure of isotactic polypropylene
    Horvath, Zs.; Sajo, I. E.; Stoll, K.; Menyhard, A.; Varga, J.
    eXPRESS Polymer Letters (2010), 4 (2), 101-114CODEN: PLOEAK; ISSN:1788-618X. (Budapest University of Technology and Economics, Dep. of Polymer Engineering)
    This study is devoted to the investigation of the effect of mol. mass on the α-, β- and γ-crystn. tendency of isotactic polypropylene (iPP). The cryst. structure was studied by wide angle x-ray scattering (WAXS) and by polarized light microscopy (PLM). The melting and crystn. characteristics were detd. by differential scanning calorimetry (DSC). The results indicate clearly that iPP with low mol. mass crystallizes essentially in α-modification. However, it crystallizes in β-form in the presence of a highly efficient and selective β-nucleating agent. The α- and β-modifications form in wide mol. mass range. The decreasing mol. mass results in increased structural instability in both α- and β-modifications and consequently enhanced inclination to recrystn. during heating. The formation of γ-modification could not be obsd., although some literature sources report that γ-form develops in iPP with low mol. mass.
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    Bessif, B.; Heck, B.; Pfohl, T.; Minh, C.; Le, Q.; Chemtob, A.; Pirela, V.; Elgoyhen, J.; Tomovska, R.; Müller, A. J.; Reiter, G. Nucleation Assisted through the Memory of a Polymer Melt: A Different Polymorph Emerging from the Melt of Another One. Macromolecules 2023, 56, 1461– 1470,  DOI: 10.1021/acs.macromol.2c02252
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    Nucleation Assisted through the Memory of a Polymer Melt: A Different Polymorph Emerging from the Melt of Another One
    Bessif, Brahim; Heck, Barbara; Pfohl, Thomas; Le, Cuong Minh Quoc; Chemtob, Abraham; Pirela, Valentina; Elgoyhen, Justine; Tomovska, Radmila; Mueller, Alejandro J.; Reiter, Guenter
    Macromolecules (Washington, DC, United States) (2023), 56 (4), 1461-1470CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    We present investigations of the intricate crystn. and melting behavior of an alternating copolymer synthesized by photopolymn. of 2,2'-dimercaptodiethyl sulfide with di(ethylene glycol)divinyl ether. Upon increasing temp., we obsd. the succession of two distinctly sepd. melting processes, which we related to the sequential formation and disappearance of two cryst. polymorphs. Due to their well-sepd. melting temps. Tm1 and Tm2, we labeled these polymorphs as LOW-Tm-form and HIGH-Tm-form, resp. X-ray diffraction results confirmed differences in the parameters of the crystal unit cells. However, upon cooling from the isotropic melt, we never obtained the HIGH-Tm-form and could only generate the LOW-Tm-form characterized by spherulitic crystals that melted completely at Tm1. Surprisingly, simultaneously everywhere within these molten spherulites, a large no. of needle-like crystals were growing as a function of the time the sample was kept (well) above Tm1. All crystals exhibited an orientation largely following the radial direction of the initial spherulites. This observation suggests that molten polymer chains remembered for some time their previous alignment within the cryst. LOW-Tm-form. This memory assisted the nucleation and thus exclusively enabled the formation of the HIGH-Tm-form. Only when partially crystg. a sample above Tm1 in the HIGH-Tm-form and subsequently cooling it below Tm1 allowed to achieve coexistence of both polymorphs. When heating such a sample of coexisting cryst. structures above Tm1, only the LOW-Tm-form melted and the HIGH-Tm-form remained. The generality of our findings has been demonstrated by similar results obtained for complementary alternating copolymers. Our study suggests that the otherwise impossible nucleation of polymorphs with a high melting temp. can be enabled by prior orientation of chains within another easily established polymorph characterized by a lower melting temp.
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    Sangroniz, L.; Cavallo, D.; Müller, A. J. Self-Nucleation Effects on Polymer Crystallization. Macromolecules 2020, 53, 4581– 4604,  DOI: 10.1021/ACS.MACROMOL.0C00223
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    Self-Nucleation Effects on Polymer Crystallization
    Sangroniz, Leire; Cavallo, Dario; Muller, Alejandro J.
    Macromolecules (Washington, DC, United States) (2020), 53 (12), 4581-4604CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    A review. The existence of a "memory" of the previous cryst. state, which survives melting and enhances recrystn. kinetics by a self-nucleation process, is well-known in polymer crystn. studies. Despite being extensively investigated, since the early days of polymer crystn. studies, a complete understanding of melt memory effects is still lacking. In particular, the exact constitution of self-nuclei is still under debate. In this Perspective, we provide a comprehensive and crit. overview of melt memory effects in polymer crystn. After the phenomenol. of the process and some key concepts are introduced, the main exptl. results of the past decades are summarized. Analogies and discrepancies of the melt memory characteristics of different polymeric systems are highlighted. Based on this background, the most significant interpretations and theories of melt memory effects are described, underlining that different interpretations may apply to various specific cases. Recent insights into self-nucleation, gained thanks to a multitechnique approach (combining calorimetry, rheol., and IR and dielec. spectroscopies), are presented. The role of intra/interchain segmental contacts in the strength of melt memory effects, and the differences between homopolymers and copolymers behavior, are discussed. Finally, we identify areas where further research in the field is needed to shed light on the long-standing questions regarding the origin of melt memory effects in semicryst. polymers.
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    Hedges, L. O.; Whitelam, S. Limit of Validity of Ostwalds Rule of Stages in a Statistical Mechanical Model of Crystallization. J. Chem. Phys. 2011, 135, 164902,  DOI: 10.1063/1.3655358
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    Limit of validity of Ostwald's rule of stages in a statistical mechanical model of crystallization
    Hedges, Lester O.; Whitelam, Stephen
    Journal of Chemical Physics (2011), 135 (16), 164902/1-164902/7CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    We have only rules of thumb with which to predict how a material will crystallize, chief among which is Ostwald's rule of stages. It states that the first phase to appear upon transformation of a parent phase is the one closest to it in free energy. Although sometimes upheld, the rule is without theor. foundation and is not universally obeyed, highlighting the need for microscopic understanding of crystn. controls. Here we study in detail the crystn. pathways of a prototypical model of patchy particles. The range of crystn. pathways it exhibits is richer than can be predicted by Ostwald's rule, but a combination of simulation and analytic theory reveals clearly how these pathways are selected by microscopic parameters. Our results suggest strategies for controlling self-assembly pathways in simulation and expt. (c) 2011 American Institute of Physics.
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    Tavassoli, Z.; Sear, R. P. Homogeneous Nucleation near a Second Phase Transition and Ostwald’s Step Rule. J. Chem. Phys. 2002, 116, 5066– 5072,  DOI: 10.1063/1.1452108
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    Homogeneous nucleation near a second phase transition and Ostwald's step rule
    Tavassoli, Z.; Sear, R. P.
    Journal of Chemical Physics (2002), 116 (12), 5066-5072CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    Homogeneous nucleation of the new phase of one transition near a 2nd phase transition is considered. The system has two phase transitions, the authors study the nucleation of the new phase of one of these transitions under conditions such that the authors are near or at the 2nd phase transition. The 2nd transition is an Ising-type transition and lies within the coexistence region of the 1st transition. The 1st transition can be any strongly 1st-order phase transition. It effects the formation of the new phase in two ways. The 1st is by reducing the nucleation barrier to direct nucleation. The 2nd is by the system undergoing the 2nd transition and transforming to a state in which the barrier to nucleation is greatly reduced. The 2nd way occurs when the barrier to undergoing the 2nd phase transition is less than that of the 1st phase transition, and is in accordance with Ostwald's rule.
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    Schick, C.; Mathot, V. Fast Scanning Calorimetry; Schick, C.; Mathot, V., Eds.; Springer Cham, 2016.
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    Schick, C.; Androsch, R. New Insights into Polymer Crystallization by Fast Scanning Chip Calorimetry. In Fast Scanning Calorimetry ; 2016; vol 91, pp 463– 535.
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    Schawe, J. E. K.; Ag, M.; Schwerzenbach, C. Flash DSC 1: A Novel Fast Differential Scanning Calorimeter. 27th World Congress of the Polymer Processing Society 2011, 27, 1– 4
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    Toda, A.; Androsch, R.; Schick, C. Insights into Polymer Crystallization and Melting from Fast Scanning Chip Calorimetry. Polymer 2016, 91, 239– 263,  DOI: 10.1016/J.POLYMER.2016.03.038
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  1. Justine Elgoyhen, Valentina Pirela, Alejandro J. Müller, Radmila Tomovska. Synthesis and Crystallization of Waterborne Thiol–ene Polymers: Toward Innovative Oxygen Barrier Coatings. ACS Applied Polymer Materials 2023, 5 (11) , 8845-8858. https://doi.org/10.1021/acsapm.3c01128
  2. Valentina Pirela, Leire Unanue, Justine Elgoyhen, Javier Ramos, Juan Francisco Vega, Agurtzane Mugica, Manuela Zubitur, Cuong Minh Quoc Le, Abraham Chemtob, Radmila Tomovska, Günter Reiter, Jaime Martín, Alejandro J. Müller. Effect of chemical structure on the crystallization kinetics of triple polymorphic high-sulfur-content polythioethers. European Polymer Journal 2025, 225 , 113721. https://doi.org/10.1016/j.eurpolymj.2025.113721
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  • Abstract

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    Scheme 1

    Scheme 1. Reaction for the Formation of DMDS-alt-DVE
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    Figure 1

    Figure 1. Thermal behavior of the DMDS-alt-DVE alternating copolymer determined via DSC, μ-DSC, and FSC. (A) DSC scans at 20 °C/min; (B) μ-DSC scans at 0.2 °C/min. (C) Thermal protocol employed for isothermal crystallization in FSC. (D) FSC heating scans (“Analysis Scan”) after isothermal crystallization for 24 h at varying Tc. The arrows point to the peaks corresponding to H – Tm, L – Tm, or VL – Tm forms, respectively and the curves correspond to: first heating (black), cooling (blue), and second heating (red).”

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    Figure 2

    Figure 2. PLOM images of the H – Tm form of the alternating copolymer DMDS-alt-DVE after (A) isothermal crystallization at Tc = 70 °C for ca. 32 h and (B) after self-seeding from the L – Tm form and isothermal crystallization at Tc = 70 °C for 30 min.

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    Figure 3

    Figure 3. Thermal behavior of alternating copolymer DMDS-alt-DVE under non-isothermal conditions via FSC. The arrows indicate the distinct phases found during heating at a constant rate of 1000 °C/s, pointing to the peaks corresponding to the L – Tm and VL – Tm forms, respectively.

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    Figure 4

    Figure 4. (A) Thermal protocol for isothermal crystallization experiments employed at varying Tc. (B) FSC heating scans at a heating rate of 4000 °C/s, after 1 h isothermal crystallization at the indicated values of Tc. The brackets point to the range of temperatures corresponding to the H – Tm, L – Tm, or VL – Tm forms, respectively.

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    Figure 5

    Figure 5. FSC experiments on alternating copolymer DMDS-alt-DVE. (A) Thermal protocol employed to achieve all three polymorphs of this alternating copolymer within the same sample. (B) FSC results obtained during the analysis (heating) scan shown in the protocol described in (A). All heating and cooling rates for this experiment were 1000 °C/s. The arrows point to the endothermic peaks corresponding to melting of the VL – Tm, L – Tm, and H – Tm forms, respectively.

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    Figure 6

    Figure 6. Isothermal WAXS diffractograms measured at (A) −5 °C (green curve) and 35 °C (black curve) by increasing the temperature in steps of 5 °C after being stored for four days at RT = 20 °C (red curve) and at 90 °C, (amorphous background, blue curve) and (B) −10 °C (black curve) in steps of 5 °C up to 5 °C and left for four days (after 30 min = red curve; 24 h = purple curve; 96 h = green curve) and after heating it to 20 °C (blue curve).

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  • References

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      A review. Future advancement of coatings relies on new synthetic building blocks and methods that enable added functionality, while minimising the environmental impact and cost. This review highlights the use of thiol-ene chem. for surface modification and coatings, a topic of increasing interest in academic and industrial context since the beginning of this century. This chem. platform has the advantages of rapid and uniform crosslinking, delayed gelation, reduced shrinkage, and insensitivity to oxygen. Recently, it resulted in significant advances in UV-cured coatings, including pigmented acrylate coatings and waterborne polyurethane dispersions. Moreover, biobased coatings were developed via thiol-ene coupling of unsatd. moieties in vegetable oils with multifunctional thiols, resulting in tunable properties. The homogeneous thiol-ene network formation has also been employed in hybrid coatings, yielding synergistic effects of the inorg. components within the thiol-ene matrix. Moreover, the UV-triggered thiol-ene reaction is fast and efficient, which is useful for surface modification with spatial and temporal control. In general, this review will critically describe how thiol-ene chem. became a powerful tool for the sustainable development of functional coating materials and surfaces with a variety of building blocks.
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      Historically, the synthesis of aq. polymer dispersions has focused on radical chain-growth polymn. of low-cost acrylate or styrene emulsions. Herein, we demonstrate the potential of UV-initiated thiol-ene step-growth radical polymn., departing from a nontransparent difunctional monomer miniemulsion based on ethylene glycol dithiol and diallyl adipate. Performed without solvent and at ambient conditions, the photopolymn. process is energy-effective, environmentally friendly, and ultrafast, leading to full monomer consumption in 2 s, upon irradiating a miniemulsion contained in a 1 mm thick quartz cell microreactor. The resultant linear poly(thioether ester) particles have an av. diam. of 130 nm. After water evapn., they yield a clear elastomeric film combining chem. resistance and high degree of crystallinity (55%).
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      A review. This contribution serves as an update to a previous review (Polym. Chem. 2010, 1, 17-36) and highlights recent applications of thiol-ene 'click' chem. as an efficient tool for both polymer/materials synthesis as well as modification. This current contribution covers examples from the literature published up to ca. mid 2013. It is not intended to be exhaustive but rather serves to highlight many of the new and exciting applications where researchers have applied thiol-ene chem. in advanced macromol. engineering and materials chem.
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      Jasinski, F.; Schweitzer, J.; Fischer, D.; Lobry, E.; Croutxe, C.; Schmutz, M.; Le Nouen, D.; Criqui, A.; Chemtob, A. Thiol–Ene Linear Step-Growth Photopolymerization in Miniemulsion: Fast Rates, Redox-Responsive Particles, and Semicrystalline Films. Macromolecules 2016, 49, 1143– 1153,  DOI: 10.1021/acs.macromol.5b02512
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      Radical step-growth photopolymn. of dithiol-diene monomer miniemulsion is shown to be a highly efficient, robust, and versatile route to generate film-forming linear poly(thioether) latexes. At extremely fast rates, the process results in high-mol.-wt. polysulfide products, exhibiting both semicryst. and oxidn.-responsive properties. Four key issues are addressed as regards the practical implementation of this novel UV-driven waterborne technol.: the prepn. of a photolatent and colloidally stable thiol-ene monomer miniemulsion, the identification of key exptl. parameters controlling reaction kinetics and polymer microstructure, the characterization of film semicrystallinity, and the application of poly(thioether ester) latexes as dual-stimuli-responsive nanocarriers sensitive to both oxidn. and hydrolysis.
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      Le, C. M. Q.; Schrodj, G.; Ndao, I.; Bessif, B.; Heck, B.; Pfohl, T.; Reiter, G.; Elgoyhen, J.; Tomovska, R.; Chemtob, A. Semi-Crystalline Poly(Thioether) Prepared by Visible-Light-Induced Organocatalyzed Thiol-Ene Polymerization in Emulsion. Macromol. Rapid Commun. 2022, 43, 2100740  DOI: 10.1002/marc.202100740
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      Semi-Crystalline Poly(thioether) Prepared by Visible-Light-Induced Organocatalyzed Thiol-ene Polymerization in Emulsion
      Le, Cuong Minh Quoc; Schrodj, Gautier; Ndao, Ibrahima; Bessif, Brahim; Heck, Barbara; Pfohl, Thomas; Reiter, Guenter; Elgoyhen, Justine; Tomovska, Radmila; Chemtob, Abraham
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      A photocatalytic thiol-ene aq. emulsion polymn. under visible-light is described to prep. linear semicryst. latexes using 2,2'-dimercaptodiethyl sulfide as dithiol and various dienes. The procedure involves low irradiance (3 mW cm-2), LED irradn. source, eosin-Y disodium as organocatalyst, low catalyst loading (<0.05% mol), and short reaction time scales (<1 h). The resulting latexes have mol. wts. of about 10 kg mol-1, av. diams. of 100 nm, and a linear structure consisting only of thioether repeating units. Electron-transfer reaction from a thiol to the triplet excited state of the photocatalyst is suggested as the primary step of the mechanism (type I), whereas oxidn. by singlet oxygen generated by energy transfer has a negligible effect (type II). Only polymers prepd. with aliph. dienes such as diallyl adipate or di(ethylene glycol) divinyl ether exhibit a high crystn. tendency as revealed by differential scanning calorimetry, polarized optical microscopy, and X-ray diffraction. Ordering and crystn. are driven by mol. packing of poly(thioether) chains combining structural regularity, compactness, and flexibility.
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      Complex and unique polymer colloids have been prepd. by miniemulsion polymn. through particle nucleation confined to monomer droplets. Unlike radical chain polymn., the reaction conditions for a predominant droplet nucleation have not been investigated in step polymns. such as thiol-ene polymn. To clarify this issue, an aq. thiol-ene miniemulsion based on diallyl phthalate and 2,2-(ethylenedioxy)diethanedithiol is prepd. Droplet stability is affected by Ostwald ripening due to the limited soly. of hexadecane (costabilizer) in the monomer phase. The control of chem. stability is also difficult, since a self-initiated polymn. is caused by adventitious radicals generated in the emulsification stage (ultrasonication). However, the addn. of an appropriate concn. of a radical scavenger (quinone) can halt polymn. for several hours. Under these conditions, batch photopolymn. kinetics, mol. wt. progress and particle size distribution have been detd. with reproducible results. Emphasis is placed on understanding how initiator soly., droplet size and monomer soly. affect droplet nucleation. For this purpose, a reliable measurement of droplet (particle) size distributions is achieved by combining size data from dynamic light scattering and transmission electron microscopy. Only when the droplet diam. is low enough (about 100 nm), then droplet nucleation prevails. Conversely, a water-insol. initiator drives a robust and complete droplet nucleation irresp. of the reaction conditions.
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      Durham, O. Z.; Krishnan, S.; Shipp, D. A. Polymer Microspheres Prepared by Water-Borne Thiol-Ene Suspension Photopolymerization. ACS Macro Lett. 2012, 1, 1134– 1137,  DOI: 10.1021/MZ300358J
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      Polymer Microspheres Prepared by Water-Borne Thiol-Ene Suspension Photopolymerization
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      Thiol-ene polymns. are possible in a water-borne suspension-like photopolymn. and yield spherical particles that have diams. in the range of submicrometers to hundreds of micrometers. This is the first report of such colloidal thiol-ene polymns. Thiol-ene polymn. offers unique conditions not commonly assocd. with a water-borne polymn. including a step-growth polymn. mechanism along with photoinitiation under ambient conditions. Example polymns. of a triene, 3,5-triallyl-1,3,5-triazine-2,4,6 (1N,3H,5H)-trione (TTT), and a tetrathiol, pentaerythritol tetrakis(3-mercaptopropionate) (PETMP), with the photoinitiator 1-hydroxycyclohexyl Ph ketone, surfactant sodium dodecyl sulfate (SDS), and a cosolvent (chloroform or toluene) are discussed. Various exptl. parameters were examd. such as surfactant concn., homogenization energy, cosolvent species, and cosolvent amt. to develop an understanding of the mechanism of microsphere formation. Particle size is dependent on homogenization energy, with greater mech. shear yielding smaller particles. In addn., higher concns. of surfactant or solvent also produced smaller spherical particles. These observations lead to the conclusion that the particles are formed via a suspension-like polymn.
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      Kitamura, M. Strategy for Control of Crystallization of Polymorphs. CrystEngComm 2009, 11, 949– 964,  DOI: 10.1039/B809332F
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      Strategy for control of crystallization of polymorphs
      Kitamura, Mitsutaka
      CrystEngComm (2009), 11 (6), 949-964CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
      A review. The controlling factor and mechanism of the crystn. of polymorphs were investigated in various systems; i.e. amino acids, inorg. compds. (calcium carbonate), pharmaceuticals and inclusion compds. The controlling factor depends on the systems (compds. and solvents and additives) and the crystn. methods (cooling crystn., reactive crystn. and anti-solvent crystn.). The controlling factors for each system were found and a schematic diagram was shown. The mechanism of each controlling factor was investigated and some rules were found. It appears that the establishment of "Ostwald's step rule" depends on the systems. In the cooling crystn. of amino acids (L-glutamic acid and L-histidine), the "Ostwald's step rule" cannot be obsd.; however, in the crystn. of BPT esters, it is clearly established. The difference of the temp. effect between L-glutamic acid and L-histidine polymorphs may be related to the difference of the mol. conformation between the polymorphs. In the reactive crystn. of calcium carbonate polymorphs, the concn. (supersatn.) of reactant solns., the mixing rate of the solns., pH, stirring rate and temp. were found to be the controlling factors for the morphol. and the crystn. behavior of polymorphs. As for the effect of additives it should be noted that the additive affects not only one polymorph, but each polymorph. Then, knowing the relative effect of additives on each polymorph is important for the control. The growth kinetics of polymorphs of L-glutamic acid and the mechanism of morphol. change of each polymorph were examd. in the presence of L-phenylalanine (as an additive) with batch crystn. and the single crystal method. The growth rate model including the additive concn. was proposed for each polymorph and the method of the selective crystn. of the polymorphs by controlling the supersatn. and the additive concn. was also indicated. In anti-solvent crystn. of pharmaceuticals (BPT) it was shown that the addn. rate of anti-solvent, initial concn. of solute and temp. are the controlling factors. With the increase of the addn. rate the water compn. in the nucleation zone increases, resulting in the preferential crystn. of the hydrate crystals. The transformation from BH to A form was obsd., however, the transformation rate increased with a decrease in the water addn. rate. Even when none of the A form was detected by XRD a small amt. of fine crystals (A form) is included within the BH crystals and act as seed crystals for the transformation. Furthermore, the change in the mol. structure is related to a dynamic change of the polymorphic crystn. behavior as obsd. in L-Glu and L-His systems. The dependence of the polymorphic crystn. behavior on the mol. structure was systematically investigated using the newly synthesized BPT esters. It appeared that the conformational flexibility, the size of alkyl group of the esters and the presence of functional group influences the formation of hydrogen bond and the polymorphism. The solvent effect on the polymorphism was also examd. in relation to the mol. structure. The functionality of clathrate crystals and the sepn. efficiency of isomers by clathrate crystals depend on their polymorphic crystn. behavior. The mechanism of the mol. recognition for the guest isomers by the host mol. is clarified. It was also elucidated that the release process of a guest biocide mol. from clathrate crystals includes polymorphic transformation.
    15. 15
      De Rosa, C.; Auriemma, F.; Malafronte, A.; Scoti, M. Crystal Structures and Polymorphism of Polymers: Influence of Defects and Disorder. Polym. Cryst. 2018, 1, e10015  DOI: 10.1002/pcr2.10015
      There is no corresponding record for this reference.
    16. 16
      Gentili, D.; Gazzano, M.; Melucci, M.; Jones, D.; Cavallini, M. Polymorphism as an Additional Functionality of Materials for Technological Applications at Surfaces and Interfaces. Chem. Soc. Rev. 2019, 48, 2502– 2517,  DOI: 10.1039/C8CS00283E
      16
      Polymorphism as an additional functionality of materials for technological applications at surfaces and interfaces
      Gentili, Denis; Gazzano, Massimo; Melucci, Manuela; Jones, Derek; Cavallini, Massimiliano
      Chemical Society Reviews (2019), 48 (9), 2502-2517CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      Polymorphism is a widespread phenomenon occurring in many solid materials having important effects in many scientific disciplines. Since mol. packing can det. the functional properties of materials but is often difficult to control, polymorphism has usually been considered a drawback for technol. applications. Thanks to advances in its control over the past few years, polymorphism is now often considered more as an opportunity because it allows a much wider range of functionality in, for example, a solid mol. material, where a corresponding packing type can be selected or even promoted. This tutorial review introduces the reader to the most representative progress in applications of polymorphism as an addnl. functionality of materials esp. in its current promise for technol. applications. In addn., it examines the most powerful strategies to control and fully exploit the intrinsic properties of polymorphism and transitions between its various metastable states, through fine-tuning of mol. packing in a reproducible manner. The aim is to create awareness about polymorphism as a novel enabling technol. rather than as a problem.
    17. 17
      De Rosa, C.; Scoti, M.; Di Girolamo, R.; de Ballesteros, O. R.; Auriemma, F.; Malafronte, A. Polymorphism in Polymers: A Tool to Tailor Material’s Properties. Polym. Cryst. 2020, 3, 1– 29,  DOI: 10.1002/PCR2.10101
      There is no corresponding record for this reference.
    18. 18
      Brittain, H. G. Polymorphism in Pharmaceutical Solids, 2nd edition; Brittain, H. G., Ed.; CRC Press: Milford, 2009; vol 192.
      There is no corresponding record for this reference.
    19. 19
      Liu, C.; Brandenburg, J. G.; Valsson, O.; Kremer, K.; Bereau, T. Free-Energy Landscape of Polymer-Crystal Polymorphism. Soft Matter 2020, 16, 9683– 9692,  DOI: 10.1039/D0SM01342K
      19
      Free-energy landscape of polymer-crystal polymorphism
      Liu, Chan; Brandenburg, Jan Gerit; Valsson, Omar; Kremer, Kurt; Bereau, Tristan
      Soft Matter (2020), 16 (42), 9683-9692CODEN: SMOABF; ISSN:1744-6848. (Royal Society of Chemistry)
      Polymorphism rationalizes how processing can control the final structure of a material. The rugged free-energy landscape and exceedingly slow kinetics in the solid state have so far hampered computational investigations. We report for the first time the free-energy landscape of a polymorphic cryst. polymer, syndiotactic polystyrene. Coarse-grained metadynamics simulations allow us to efficiently sample the landscape at large. The free-energy difference between the two main polymorphs, α and β, is further investigated by quantum-chem. calcns. The results of the two methods are in line with exptl. observations: they predict β as the more stable polymorph under std. conditions. Critically, the free-energy landscape suggests how the α polymorph may lead to exptl. obsd. kinetic traps. The combination of multiscale modeling, enhanced sampling, and quantum-chem. calcns. offers an appealing strategy to uncover complex free-energy landscapes with polymorphic behavior.
    20. 20
      Keller, A.; Cheng, S. Z. D. The Role of Metastability in Polymer Phase Transitions. Polymer 1998, 39, 4461– 4487,  DOI: 10.1016/S0032-3861(97)10320-2
      There is no corresponding record for this reference.
    21. 21
      Zheng, Y.; Pan, P. Crystallization of Biodegradable and Biobased Polyesters: Polymorphism, Cocrystallization, and Structure-Property Relationship. Prog. Polym. Sci. 2020, 109, 101291  DOI: 10.1016/J.PROGPOLYMSCI.2020.101291
      21
      Crystallization of biodegradable and biobased polyesters: Polymorphism, cocrystallization, and structure-property relationship
      Zheng, Ying; Pan, Pengju
      Progress in Polymer Science (2020), 109 (), 101291CODEN: PRPSB8; ISSN:0079-6700. (Elsevier Ltd.)
      In the past two decades, synthetic biodegradable and biobased polyesters have emerged as a sustainable alternative to traditional petroleum-derived polymers for diverse range of applications. Most of the synthetic biodegradable and biobased polyesters are semicryst. Some of these polymers can exist in a variety of polymorphs depending on the crystn. and processing conditions. In addn., blends or copolymers can exhibit cocrystn. behavior (such as stereocomplex, isomorphic, and isodimorphic crystn.). Polymorphic crystn. and cocrystn. of polymers plays an essential role not only in the scientific understanding of condensed matter structures of polymers, but also in the technol. development and application of this new class of materials. This paper reviews the recent progress in the understanding of the polymorphic crystn., co-crystn., and structure-property relationship of synthetic biodegradable and biobased polyesters that has occurred within the past decade. Particular focus is on the structure, morphol., formation kinetics, and phase transition of crystals grown from biodegradable and biobased polyesters. Since the phys. properties of polymers depend on their crystal structure and morphol., we also reviewed the relationships between the crystn. and processing conditions, cryst. structure and morphol., and phys. properties (e.g., mech. and biodegradability) of biodegradable and biobased polymorphic, cocrystallizable polyesters.
    22. 22
      Wu, X.; Shi, S.; Yu, Z.; Russell, T. P.; Wang, D. AFM Nanomechanical Mapping and Nanothermal Analysis Reveal Enhanced Crystallization at the Surface of a Semicrystalline Polymer. Polymer 2018, 146, 188– 195,  DOI: 10.1016/J.POLYMER.2018.05.043
      22
      AFM nanomechanical mapping and nanothermal analysis reveal enhanced crystallization at the surface of a semicrystalline polymer
      Wu, Xuefei; Shi, Shaowei; Yu, Zhongzhen; Russell, Thomas P.; Wang, Dong
      Polymer (2018), 146 (), 188-195CODEN: POLMAG; ISSN:0032-3861. (Elsevier Ltd.)
      We used at. force microscopy (AFM) nanomech. mapping to image the surface of a semicryst. polymer, specifically polymorphic isotactic poly (1-butene) (iPB), to det. the mech. properties of a surface layer, and compared this to the properties in the bulk. The measured Young's modulus of the surface layer as a function of annealing time at room temp. was found to be higher than that of the bulk, indicating a more rapid transformation from form II to I polymorphs and an enhanced movement of polymer chain segments at the surface relative to the bulk for this polymer. Plate-like crystals were found at the surface and, as the annealing temp. increased from 70 to 110 °C, evidence of a surface layer was found that increased in thickness from ∼30 to ∼130 nm, resp. After removing this layer, the morphol. found in the bulk was markedly different. We also used AFM nanothermal anal. to det. the local m.p. (Tm) and found, that the m.p., Tm, of the crystals at the surface was higher than that of the bulk, in keeping with the modulus measurements. The nanomech. and nanothermal properties and the morphol. at the surface suggest an enhanced movement of polymer chain segments at the surface and therefore, an enhanced crystn. at the surface.
    23. 23
      Marigo, A.; Marega, C.; Cecchin, G.; Collina, G.; Ferrara, G. Phase Transition II → I in Isotactic Poly-1-Butene: Wide- and Small-Angle X-Ray Scattering Measurements. Eur. Polym. J. 2000, 36, 131– 136,  DOI: 10.1016/S0014-3057(99)00043-9
      23
      Phase transition II → I in isotactic poly-1-butene: wide- and small-angle X-ray scattering measurements
      Marigo, Antonio; Marega, Carla; Cecchin, Giuliano; Collina, Gianni; Ferrara, Giuseppe
      European Polymer Journal (1999), 36 (1), 131-136CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Science Ltd.)
      Phase transition II → I in isotactic poly-1-butene was studied by wide- and small-angle X-ray scattering in order to follow the change of crystallinity and of the characteristic parameters of the lamellar stacks over time. Small-angle X-ray scattering exptl. patterns were analyzed by a fitting method with the profiles calcd. from some theor. distribution models of the lamellar thickness. The math. evaluation of small-angle X-ray scattering patterns provided crystallinity values which were compared with those obtained by wide-angle X-ray scattering, in order to obtain information on the lamellar stacks organization. The transition nucleation seems to be localized on lamellar distortion points and the transition itself involves the rearrangement of lamellae and of lamellar stacks.
    24. 24
      Azzurri, F.; Flores, A.; Alfonso, G. C.; Baltá Calleja, F. J. Polymorphism of Isotactic Poly(1-Butene) as Revealed by Microindentation Hardness. 1: Kinetics of the Transformation. Macromolecules 2002, 35, 9069– 9073,  DOI: 10.1021/ma021005e
      24
      Polymorphism of isotactic poly(1-butene) as revealed by microindentation hardness. 1. Kinetics of the transformation
      Azzurri, F.; Flores, A.; Alfonso, G. C.; Balta Calleja, F. J.
      Macromolecules (2002), 35 (24), 9069-9073CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      The microindentation hardness technique has been employed to examine the II → I polymorphic transformation of isotactic poly-1-butene taking place upon aging at room temp. The hardness values of form I are shown to be remarkably higher than those of form II due to the denser packing of chains in the hexagonal crystal modification. The kinetics of the II → I transformation has been followed by means of microindentation hardness measurements in real time. The influence of molar mass and crystn. temp. on the kinetics of the polymorphic transformation is examd. Results suggest that the rate of polymorphic transformation is independent of mol. wt. In addn., it is seen that increasing the crystn. temp. (up to 105 °C) notably reduces the time required for a full transformation of form II into form I. The influence of the fraction of amorphous material on the rate of polymorphic transformation is discussed.
    25. 25
      Cavallo, D.; Kanters, M. J. W.; Caelers, H. J. M.; Portale, G.; Govaert, L. E. Kinetics of the Polymorphic Transition in Isotactic Poly(1-Butene) under Uniaxial Extension. New Insights from Designed Mechanical Histories. Macromolecules 2014, 47, 3033– 3040,  DOI: 10.1021/ma500281f
      25
      Kinetics of the Polymorphic Transition in Isotactic Poly(1-butene) under Uniaxial Extension. New Insights From Designed Mechanical histories.
      Cavallo, Dario; Kanters, Marc J. W.; Caelers, Harm J. M.; Portale, Giuseppe; Govaert, Leon E.
      Macromolecules (Washington, DC, United States) (2014), 47 (9), 3033-3040CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Isotactic poly(1-butene) (i-PBu) crystallizes upon cooling from the melt in a metastable tetragonal structure (form II), which slowly evolves toward the state of ultimate stability, i.e., the trigonal form I. It is well-known that this polymorphic transformation, which typically requires few weeks at room temp., can be greatly accelerated by the application of mech. stresses and/or deformation. However, the exact mechanism of this kinetics enhancement is not completely understood. In this work, the polymorphic transformation of i-PBu under tensile deformation is investigated in details. Thanks to properly designed mech. histories-including expts. at different true strain and true stress rates-and to in situ wide-angle X-ray diffraction expts., the role of the various deformation parameters is elucidated. The use of different time scales during the expts. enabled us to gain kinetics data on the transition, information which is disregarded in current literature. The set of expts. performed permit to highlight a stress-driven mechanism, active up to a fraction of transformed form I of about 0.4-0.5. After this value is reached, the stress-transformation time superposition principle does not hold anymore and the transition kinetics slows down, since a major part of the total applied stress is carried by the mech. stronger form I lamellae.
    26. 26
      Qiao, Y.; Wang, Q.; Men, Y. Kinetics of Nucleation and Growth of Form II to I Polymorphic Transition in Polybutene-1 as Revealed by Stepwise Annealing. Macromolecules 2016, 49, 5126– 5136,  DOI: 10.1021/acs.macromol.6b00862
      26
      Kinetics of Nucleation and Growth of Form II to I Polymorphic Transition in Polybutene-1 as Revealed by Stepwise Annealing
      Qiao, Yongna; Wang, Qiao; Men, Yongfeng
      Macromolecules (Washington, DC, United States) (2016), 49 (14), 5126-5136CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Kinetics of II to I polymorphic transformation in isotactic polybutene-1 (PB-1) and its annealing temp. and time dependencies have been investigated by means of differential scanning calorimetry and in situ wide-angle X-ray diffraction techniques. The PB-1 samples were isothermally crystd. into metastable form II cryst. modification followed by annealing at a lower temp. (Tl) and at a higher temp. (Th) subsequently or at a single temp. (Ts) to promote polymorphic transition from form II to I. This solid-to-solid phase transition was shown to be a two-step process including nucleation and growth suggested by the result that more form I was obtained after being annealed at Tl and Th than annealed at Ts for the same period. Annealing at Tl benefits nucleation due to internal stress induced by unbalanced shrinkage of amorphous and cryst. phases because of their different thermal expansion coeffs., while annealing at Th is beneficial to growth owing to rapid segmental diffusion at that temp. At a given annealing time at Tl (tl) and at Th (th), and fixing one of temps. between Tl and Th, it shows a max. in the transformation-temp. profile that can be correlated with the optimal temp. for nucleation or growth. The phase transition was efficiently accelerated with the increase of isothermal crystn. temp. Such dependency can be understood as a result of higher internal stress built up during cooling from higher isothermal crystn. temp. to Tl. Our results decompd. the polymorphic transition into nucleation and growth for the first time providing a simple and effective way for rapid transition of form II to I in PB-1.
    27. 27
      Xiao, W.; Wu, P.; Feng, J.; Yao, R. Influence of a Novel β-Nucleating Agent on the Structure, Morphology, and Nonisothermal Crystallization Behavior of Isotactic Polypropylene. J. Appl. Polym. Sci. 2009, 111, 1076– 1085,  DOI: 10.1002/APP.29139
      27
      Influence of a novel β-nucleating agent on the structure, morphology, and nonisothermal crystallization behavior of isotactic polypropylene
      Xiao, Wenchang; Wu, Peiyi; Feng, Jiachun; Yao, Riyuan
      Journal of Applied Polymer Science (2009), 111 (2), 1076-1085CODEN: JAPNAB; ISSN:0021-8995. (John Wiley & Sons, Inc.)
      The cryst. structure, morphol., and nonisothermal crystn. behavior of isotactic polypropylene (iPP) with and without a novel rare earth-contg. β-nucleating agent (WBG) were investigated with wide-angle X-ray diffraction, polar optical microscopy, and differential scanning calorimetry. WBG could induce the formation of the β form, and a higher proportion of the β form could be obtained by the combined effect of the optimum WBG concn. and a lower cooling rate. The content of the β form could reach more than 0.90 in a 0.08% WBG nucleated sample at cooling rates lower than 5°/min. Polar optical microscopy showed that WBG led to substantial changes in both the morphol. development and crystn. process of iPP. At all the studied cooling rates, the temp. at which the max. rate of crystn. occurred was increased by 8-11° in the presence of the nucleating agent. An anal. of the nonisothermal crystn. kinetics also revealed that the introduction of WBG significantly shortened both the apparent incubation period for crystn. and the overall crystn. time.
    28. 28
      Marco, C.; Gómez, M. A.; Ellis, G.; Arribas, J. M. Activity of a β-Nucleating Agent for Isotactic Polypropylene and Its Influence on Polymorphic Transitions. J. Appl. Polym. Sci. 2002, 86, 531– 539,  DOI: 10.1002/APP.10811
      28
      Activity of β-nucleating agent for isotactic polypropylene and its influence on polymorphic transitions
      Marco, C.; Gomez, M. A.; Ellis, G.; Arribas, J. M.
      Journal of Applied Polymer Science (2002), 86 (3), 531-539CODEN: JAPNAB; ISSN:0021-8995. (John Wiley & Sons, Inc.)
      The influence of a nonpigmenting β-nucleating additive in the crystn. of isotactic polypropylene (iPP) is investigated by differential scanning calorimetry and X-ray diffraction. This additive induces the formation of a very high level of the trigonal modification of iPP. The crystn. and melting behavior of the nucleated systems are studied as a function of the cooling and heating rates and the control of the final temp. during the cooling process. The nucleating agent exerts an important effect on the crystn. temps. and the polymorphic transitions of iPP, delaying the β-α recrystn. process through an increase in the stability of the trigonal crystals.
    29. 29
      Garbarczyk, J.; Paukszta, D.; Borysiak, S. Polymorphism of Isotactic Polypropylene in Presence of Additives, in Blends and in Composites. J. Macromol. Sci. Phys. B 2002, 41, 1267– 1278,  DOI: 10.1081/MB-120013096
      There is no corresponding record for this reference.
    30. 30
      Horváth, Z.; Sajó, I. E.; Stoll, K.; Menyhárd, A.; Varga, J. The Effect of Molecular Mass on the Polymorphism and Crystalline Structure of Isotactic Polypropylene. Express Polym. Lett. 2010, 4, 101– 114,  DOI: 10.3144/EXPRESSPOLYMLETT.2010.15
      30
      The effect of molecular mass on the polymorphism and crystalline structure of isotactic polypropylene
      Horvath, Zs.; Sajo, I. E.; Stoll, K.; Menyhard, A.; Varga, J.
      eXPRESS Polymer Letters (2010), 4 (2), 101-114CODEN: PLOEAK; ISSN:1788-618X. (Budapest University of Technology and Economics, Dep. of Polymer Engineering)
      This study is devoted to the investigation of the effect of mol. mass on the α-, β- and γ-crystn. tendency of isotactic polypropylene (iPP). The cryst. structure was studied by wide angle x-ray scattering (WAXS) and by polarized light microscopy (PLM). The melting and crystn. characteristics were detd. by differential scanning calorimetry (DSC). The results indicate clearly that iPP with low mol. mass crystallizes essentially in α-modification. However, it crystallizes in β-form in the presence of a highly efficient and selective β-nucleating agent. The α- and β-modifications form in wide mol. mass range. The decreasing mol. mass results in increased structural instability in both α- and β-modifications and consequently enhanced inclination to recrystn. during heating. The formation of γ-modification could not be obsd., although some literature sources report that γ-form develops in iPP with low mol. mass.
    31. 31
      Bessif, B.; Heck, B.; Pfohl, T.; Minh, C.; Le, Q.; Chemtob, A.; Pirela, V.; Elgoyhen, J.; Tomovska, R.; Müller, A. J.; Reiter, G. Nucleation Assisted through the Memory of a Polymer Melt: A Different Polymorph Emerging from the Melt of Another One. Macromolecules 2023, 56, 1461– 1470,  DOI: 10.1021/acs.macromol.2c02252
      31
      Nucleation Assisted through the Memory of a Polymer Melt: A Different Polymorph Emerging from the Melt of Another One
      Bessif, Brahim; Heck, Barbara; Pfohl, Thomas; Le, Cuong Minh Quoc; Chemtob, Abraham; Pirela, Valentina; Elgoyhen, Justine; Tomovska, Radmila; Mueller, Alejandro J.; Reiter, Guenter
      Macromolecules (Washington, DC, United States) (2023), 56 (4), 1461-1470CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      We present investigations of the intricate crystn. and melting behavior of an alternating copolymer synthesized by photopolymn. of 2,2'-dimercaptodiethyl sulfide with di(ethylene glycol)divinyl ether. Upon increasing temp., we obsd. the succession of two distinctly sepd. melting processes, which we related to the sequential formation and disappearance of two cryst. polymorphs. Due to their well-sepd. melting temps. Tm1 and Tm2, we labeled these polymorphs as LOW-Tm-form and HIGH-Tm-form, resp. X-ray diffraction results confirmed differences in the parameters of the crystal unit cells. However, upon cooling from the isotropic melt, we never obtained the HIGH-Tm-form and could only generate the LOW-Tm-form characterized by spherulitic crystals that melted completely at Tm1. Surprisingly, simultaneously everywhere within these molten spherulites, a large no. of needle-like crystals were growing as a function of the time the sample was kept (well) above Tm1. All crystals exhibited an orientation largely following the radial direction of the initial spherulites. This observation suggests that molten polymer chains remembered for some time their previous alignment within the cryst. LOW-Tm-form. This memory assisted the nucleation and thus exclusively enabled the formation of the HIGH-Tm-form. Only when partially crystg. a sample above Tm1 in the HIGH-Tm-form and subsequently cooling it below Tm1 allowed to achieve coexistence of both polymorphs. When heating such a sample of coexisting cryst. structures above Tm1, only the LOW-Tm-form melted and the HIGH-Tm-form remained. The generality of our findings has been demonstrated by similar results obtained for complementary alternating copolymers. Our study suggests that the otherwise impossible nucleation of polymorphs with a high melting temp. can be enabled by prior orientation of chains within another easily established polymorph characterized by a lower melting temp.
    32. 32
      Sangroniz, L.; Cavallo, D.; Müller, A. J. Self-Nucleation Effects on Polymer Crystallization. Macromolecules 2020, 53, 4581– 4604,  DOI: 10.1021/ACS.MACROMOL.0C00223
      32
      Self-Nucleation Effects on Polymer Crystallization
      Sangroniz, Leire; Cavallo, Dario; Muller, Alejandro J.
      Macromolecules (Washington, DC, United States) (2020), 53 (12), 4581-4604CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      A review. The existence of a "memory" of the previous cryst. state, which survives melting and enhances recrystn. kinetics by a self-nucleation process, is well-known in polymer crystn. studies. Despite being extensively investigated, since the early days of polymer crystn. studies, a complete understanding of melt memory effects is still lacking. In particular, the exact constitution of self-nuclei is still under debate. In this Perspective, we provide a comprehensive and crit. overview of melt memory effects in polymer crystn. After the phenomenol. of the process and some key concepts are introduced, the main exptl. results of the past decades are summarized. Analogies and discrepancies of the melt memory characteristics of different polymeric systems are highlighted. Based on this background, the most significant interpretations and theories of melt memory effects are described, underlining that different interpretations may apply to various specific cases. Recent insights into self-nucleation, gained thanks to a multitechnique approach (combining calorimetry, rheol., and IR and dielec. spectroscopies), are presented. The role of intra/interchain segmental contacts in the strength of melt memory effects, and the differences between homopolymers and copolymers behavior, are discussed. Finally, we identify areas where further research in the field is needed to shed light on the long-standing questions regarding the origin of melt memory effects in semicryst. polymers.
    33. 33
      Hedges, L. O.; Whitelam, S. Limit of Validity of Ostwalds Rule of Stages in a Statistical Mechanical Model of Crystallization. J. Chem. Phys. 2011, 135, 164902,  DOI: 10.1063/1.3655358
      33
      Limit of validity of Ostwald's rule of stages in a statistical mechanical model of crystallization
      Hedges, Lester O.; Whitelam, Stephen
      Journal of Chemical Physics (2011), 135 (16), 164902/1-164902/7CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      We have only rules of thumb with which to predict how a material will crystallize, chief among which is Ostwald's rule of stages. It states that the first phase to appear upon transformation of a parent phase is the one closest to it in free energy. Although sometimes upheld, the rule is without theor. foundation and is not universally obeyed, highlighting the need for microscopic understanding of crystn. controls. Here we study in detail the crystn. pathways of a prototypical model of patchy particles. The range of crystn. pathways it exhibits is richer than can be predicted by Ostwald's rule, but a combination of simulation and analytic theory reveals clearly how these pathways are selected by microscopic parameters. Our results suggest strategies for controlling self-assembly pathways in simulation and expt. (c) 2011 American Institute of Physics.
    34. 34
      Tavassoli, Z.; Sear, R. P. Homogeneous Nucleation near a Second Phase Transition and Ostwald’s Step Rule. J. Chem. Phys. 2002, 116, 5066– 5072,  DOI: 10.1063/1.1452108
      34
      Homogeneous nucleation near a second phase transition and Ostwald's step rule
      Tavassoli, Z.; Sear, R. P.
      Journal of Chemical Physics (2002), 116 (12), 5066-5072CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      Homogeneous nucleation of the new phase of one transition near a 2nd phase transition is considered. The system has two phase transitions, the authors study the nucleation of the new phase of one of these transitions under conditions such that the authors are near or at the 2nd phase transition. The 2nd transition is an Ising-type transition and lies within the coexistence region of the 1st transition. The 1st transition can be any strongly 1st-order phase transition. It effects the formation of the new phase in two ways. The 1st is by reducing the nucleation barrier to direct nucleation. The 2nd is by the system undergoing the 2nd transition and transforming to a state in which the barrier to nucleation is greatly reduced. The 2nd way occurs when the barrier to undergoing the 2nd phase transition is less than that of the 1st phase transition, and is in accordance with Ostwald's rule.
    35. 35
      Schick, C.; Mathot, V. Fast Scanning Calorimetry; Schick, C.; Mathot, V., Eds.; Springer Cham, 2016.
      There is no corresponding record for this reference.
    36. 36
      Schick, C.; Androsch, R. New Insights into Polymer Crystallization by Fast Scanning Chip Calorimetry. In Fast Scanning Calorimetry ; 2016; vol 91, pp 463– 535.
      There is no corresponding record for this reference.
    37. 37
      Schawe, J. E. K.; Ag, M.; Schwerzenbach, C. Flash DSC 1: A Novel Fast Differential Scanning Calorimeter. 27th World Congress of the Polymer Processing Society 2011, 27, 1– 4
      There is no corresponding record for this reference.
    38. 38
      Toda, A.; Androsch, R.; Schick, C. Insights into Polymer Crystallization and Melting from Fast Scanning Chip Calorimetry. Polymer 2016, 91, 239– 263,  DOI: 10.1016/J.POLYMER.2016.03.038
      38
      Insights into polymer crystallization and melting from fast scanning chip calorimetry
      Toda, Akihiko; Androsch, Rene; Schick, Christoph
      Polymer (2016), 91 (), 239-263CODEN: POLMAG; ISSN:0032-3861. (Elsevier Ltd.)
      A review. Fast scanning chip calorimetry in its non-adiabatic version allows for heating and cooling at rates up to 106 K s-1, covering all polymer processing relevant rates. Furthermore it allows for systematic studies of nucleation, crystn., melting and reorganization for a large no. of polymers. After an introduction, open problems and the need for further investigation of polymer crystn. are explained, followed by a brief description of the novel technique of fast scanning chip calorimetry and its capability to shed further light on fundamental details of the polymer-crystn. process. In the fourth part, specific examples of non-isothermal and isothermal crystn. studies are provided, including the discussion of the effect of nucleating agents. The possibility to investigate homogeneous nucleation and its kinetics is highlighted too. The fifth part focuses on the anal. of the melting kinetics and the detn. of the zero-entropy-prodn. melting temp.
    39. 39
      Sangroniz, L.; Ocando, C.; Cavallo, D.; Müller, A. J. Melt Memory Effects in Poly(Butylene Succinate) Studied by Differential Fast Scanning Calorimetry. Polymers 2020, 12, 2796,  DOI: 10.3390/polym12122796
      39
      Melt memory effects in poly(butylene succinate) studied by differential fast scanning calorimetry
      Sangroniz, Leire; Ocando, Connie; Cavallo, Dario; Mueller, Alejandro J.
      Polymers (Basel, Switzerland) (2020), 12 (12), 2796CODEN: POLYCK; ISSN:2073-4360. (MDPI AG)
      It is widely accepted that melt memory effect on polymer crystn. depends on thermal history of the material, however a systematic study of the different parameters involved in the process has been neglected, so far. In this work, poly(butylene succinate) has been selected to analyze the effect of short times and high cooling/heating rates that are relevant from an industrial point of view by taking advantage of fast scanning calorimetry (FSC). The FSC expts. reveal that the width of melt memory temp. range is reduced with the time spent at the self-nucleation temp. (Ts), since annealing of crystals occurs at higher temps. The effectiveness of self-nuclei to crystallize the sample is addressed by increasing the cooling rate from Ts temp. The effect of previous std. state on melt memory is analyzed by (a) changing the cooling/heating rate and (b) applying successive self-nucleation and annealing (SSA) technique, observing a strong correlation between melting enthalpy or crystallinity degree and the extent of melt memory. The acquired knowledge can be extended to other semicryst. polymers to control accurately the melt memory effect and therefore, the time needed to process the material and its final performance.
    40. 40
      Schawe, J. E. K. Influence of Processing Conditions on Polymer Crystallization Measured by Fast Scanning DSC. J. Therm. Anal. Calorim. 2014, 116, 1165– 1173,  DOI: 10.1007/s10973-013-3563-8
      40
      Influence of processing conditions on polymer crystallization measured by fast scanning DSC
      Schawe, J. E. K.
      Journal of Thermal Analysis and Calorimetry (2014), 116 (3), 1165-1173CODEN: JTACF7; ISSN:1388-6150. (Springer)
      The structural formation of polymers during processing significantly influences the mech. properties and the temp. stability of polymer products. The anal. of structural formation by conventional thermal anal. techniques is limited because of the relatively low scanning rates. Thus, reorganization during heating changes the initial structure, and the applicable cooling rates are not representative for the applied cooling rates during prodn., i.e., crystn. at high supercooling cannot be investigated. To overcome these limitations, chip calorimeters with very high scanning rates have been developed. The fast scanning Flash DSC 1 based on MEMS chip-sensors allows for scanning rates up to 40,000 K s-1. In this paper, we discuss some basic concepts of chip calorimetry in general. We then study the influence of additives and mol. modifications on the structural formation at tech. relevant cooling rates. This information is crucial to adapt polymer formulation and processing conditions to specific product requirements.
    41. 41
      Furushima, Y.; Schick, C.; Toda, A. Crystallization, Recrystallization, and Melting of Polymer Crystals on Heating and Cooling Examined with Fast Scanning Calorimetry. Polym. Cryst. 2018, 1, e10005  DOI: 10.1002/PCR2.10005
      There is no corresponding record for this reference.
    42. 42
      Caputo, M. R.; Tang, X.; Westlie, A. H.; Sardon, H.; Chen, E. Y. X.; Müller, A. J. Effect of Chain Stereoconfiguration on Poly(3-Hydroxybutyrate) Crystallization Kinetics. Biomacromolecules 2022, 23, 3847– 3859,  DOI: 10.1021/acs.biomac.2c00682
      42
      Effect of Chain Stereoconfiguration on Poly(3-hydroxybutyrate) Crystallization Kinetics
      Caputo, Maria Rosaria; Tang, Xiaoyan; Westlie, Andrea H.; Sardon, Haritz; Chen, Eugene Y.-X.; Muller, Alejandro J.
      Biomacromolecules (2022), 23 (9), 3847-3859CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
      Poly(3-hydroxybutyrate) (PHB) is naturally accumulated by bacteria but can also be synthesized chem. Its processability is limited, as it tends to degrade at temps. above its melting temp.; hence, investigation into crystn. kinetics and morphol. of PHB materials of both natural and synthetic origins is of great need and interest to get a better understanding of structure-property relationship. Accordingly, this contribution reports a first study of the crystn. and morphol. of synthetic PHB materials of different mol. wts. These synthetic PHBs are racemic mixts. (50/50 mol %) of R and S chain configurations and are compared with an enantiopure bacterial R-PHB. Nonisothermal and isothermal crystn. studies show that R and S chains of PHB can cocrystallize in the same unit cell as the R-PHB. Most significantly, the results show that the presence of S chains decreases the overall crystn. rate, which could enhance the processability and industrialization of PHB-based materials.
    43. 43
      Gedde, U. W.; Hedenqvist, M. S. Fundamental Polymer Science, 2nd edition; Springer Nature: Cham, Switzerland, 2019.
      There is no corresponding record for this reference.

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    • A brief description of the synthesis of the alternating copolymer DMDS-alt-DVE, a brief description on the obtention of the molecular weight distribution, and a table containing calorimetric data of DMDS-alt-DVE obtained for different techniques and rates (PDF)


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