Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session B19: Polymer Crystals and Crystallization IIRecordings Available
|
Hide Abstracts |
Sponsoring Units: DPOLY Chair: Lucia Fernandez-Ballester, University of Nebraska - Lincoln Room: McCormick Place W-185A |
Monday, March 14, 2022 11:30AM - 12:06PM |
B19.00001: New (Macro)molecular Facets of an Old Problem: What Controls the Morphology of Semicrystalline Polymer Invited Speaker: Kay Saalwaechter In defending his “macromolecular hypothesis,” Staudinger realized early on the relevance long chain molecules being able to crystallize. Since then, a variety of theories has been set up to explain the salient features of the semicrystalline morphology found for bulk high polymers, yet most of them do not consider explicitly the effect of intracrystalline chain dynamics and entanglements in the amorphous phase on the resulting lamellar morphology. |
Monday, March 14, 2022 12:06PM - 12:18PM |
B19.00002: Molecular Dynamics and Phase Separation in Co-crystal of Crystalline/Crystalline Polymer Blend Navin K Kafle, Ying Zheng, Toshikazu Miyoshi Semicrystalline polymers are categorized as either mobile or fixed crystals, depending on chain mobility in the crystalline region. In this work, we for the first time investigate molecular dynamics and phase structure in the co-crystal consisting of fixed and mobile polymer crystals by solid-state (ss) NMR spectroscopy. It is demonstrated that i) mobile component begins large amplitude motions associated with crystal-crystal transition while fixed ones keep their rigidity in the co-crystals and ii) asymmetric molecular dynamics leads to nano-segregations into mobile- and fixed-rich domains in the co-crystal below melting temperature (Tm). The observed phase separation induced by asymmetric molecular dynamics is similar to phase separation of miscible amorphous polymer blend, however, is limited to two-dimension due to parallel packing of stems inside the co-crystal as well as chain connectivity at the crystalline-amorphous boundary. |
Monday, March 14, 2022 12:18PM - 12:30PM |
B19.00003: Minima in the temperature gradient of the crystallization rates of long-spaced polyacetals at the transition between two polymorphs Rufina G Alamo, Carlos Germosen, Stephanie F Marxsen Under isothermal crystallization (Tc) from the melt, polyacetals spaced by 12, 18, 19, or 23 methylenes develop up to four layered polymorphs. While the crystallization kinetics of the two high Tc polymorphs can be followed by classical DSC, in this presentation it will be demonstrated that the kinetics of the two low-temperature phases can be extracted via Fast Scanning Calorimetry (FSC). The unusual inversion of crystallization kinetics at Tc in the boundary between two polymorphs observed by DSC is also present for the metastable low temperature phases. While the rate minima observed when transitioning between the two highest temperature polymorphs is attributed to competition in nucleation between the two forms coupled with a self-poisoning effect, a possible heterogeneous to homogeneous nucleation change will be discussed for the transition to the lowest temperature disordered structure. Such a change in nucleation type has been posited to explain similar crystallization rate minima in other polymers at the transition between mesomorphic and crystal structures. |
Monday, March 14, 2022 12:30PM - 12:42PM |
B19.00004: Understanding the roles of molecular topology and entanglement in polymer crystallization using ring polymers Lingyi Zou, Wenlin Zhang We investigate the effects of entanglement and molecular topologies on polymer crystallization using atomistic molecular dynamics (MD) simulations of cyclic and linear polyethylene (PE). For unlinked ring polymers, the non-concatenation and non-knotting constraints induce more collapsed conformations and higher melt free energy than their linear counterparts. Using a scaling theory, we predict the enhanced melt free energy can lead to a weak melting temperature enhancement ΔTm for rings of moderate sizes. The predicted melting temperatures for ring PE agree with our atomistic MD simulation results. However, we expect ΔTm to decrease with increasing molecular weight and become negligible when the chains are much longer than the entanglement strand. Despite the similar melting temperatures, we show that the isothermal crystal nucleation of rings is much faster than that of linear PE. The lack of conventional molecular entanglements in unlinked molten rings promotes nucleation kinetics. To further demonstrate the effect of molecular entanglement on crystal nucleation, we vary the entanglement density in molten linear PE by collapsing the radii of gyration using external potentials. Although the melting temperatures of the collapsed linear chains remain the same, distinct nucleation kinetics are observed. By analyzing the entanglement topologies using the primitive path analysis (PPA), we quantify the effects of entanglement density on polymer crystal nucleation rates. |
Monday, March 14, 2022 12:42PM - 12:54PM |
B19.00005: Breaking translational symmetry in polymer crystallization Christopher Y Li, Mark C Staub, Shiche Yu, Bin Zhao While one of the fundamental laws in crystallization is translational symmetry, it is often broken in a class of polymer crystals defined as shape-symmetry incommensurate crystals (SSICs) which include helical, helicoidal, scrolled, tubular crystals, and the newly discovered crystalsomes. The reason for the broken translation symmetry in SSICs can vary, and in this talk, we discuss the chain architecture effect on polymer crystallization. While classical flat single crystals are obtained in linear polymers, non-flat spherical or tubular crystals were observed in molecular bottlebrush polymers and end-functionalized polymers. The spherical and tubular morphologies suggest the spontaneous translational symmetry breaking during crystal growth, which is attributed to lamellar imbalance associated with chain architectures. Crystallization kinetics in this class of polymers will also be discussed. |
Monday, March 14, 2022 12:54PM - 1:06PM |
B19.00006: Effect of precise and non-precise linker length, backbone polarity, and dispersity on crystallization and rheological properties of dynamic ethylene networks Bhaskar Soman, Christopher M Evans Precise placement of ionic and non-ionic side groups has been shown to have a strong impact on the crystallization of polyolefins and polyacetals, resulting in unique temperature-dependent crystal phases and enhanced proton conduction. A series of dynamic ethylene networks were synthesized with 8-18 carbons between dynamic bonds to study the effect of precise and non-precise linker length, backbone polarity and dispersity on crystallization and rheological properties of these networks. Precise and non-precise linkers show negligible differences in the rubbery plateau modulus and have similar glass transition temperatures (Tg), but the induction period for crystallization in the non-precise networks is longer than a precise network with the same average crosslink density. Comparison of the (Tg) normalized relaxation times of dynamic ethylene oxide vs dynamic ethylene networks suggests that for the same precise linker length the backbone polarity doesn’t influence relaxation behavior. Odd vs even numbered carbon linker lengths have been reported to show a periodic up-down trend in Tg, Tm, and ion conductivity in permanent networks, highlighting the importance of precise chemistry on network properties. In contrast, odd-even effect is not observed in our dynamic ethylene networks. |
Monday, March 14, 2022 1:06PM - 1:18PM |
B19.00007: A Boundary Layer Model for Steady Directional Solidification of Polymer Melts Sanat K Kumar, Christopher Durning, Sumesh P Thampi, Ahana Purushothaman, Sabin Adhikari We analyze a one-directional model for steady-state directional solidification of a polymer melt due to a heat sink moving at constant speed V . The non-linear model, couples a local heat balance to Avrami crystallization kinetics, for instantaneous nucleation with one directional spherulite growth, and weak under cooling. It properly accounts for the self-generated thermal field due to the release of latent heat behind the solidification front. Two dimensionless parameters control the predictions. The first, e , a scaled characteristic crystallization time, typically small in prior experimental work, controls the width of a boundary layer adjacent to the liquid melt, wherein crystallinity develops almost completely. The second, v, a scaled sink speed, also typically small, together with e , control the thickness of the solidified layer between the melt and the thermal sink. The global features predicted by a perturbation analysis (e.g. width of the solid layer versus sink speed) are consistent with the simple Stefan model. Comparison with numerical solutions confirm the key analytical predictions. Importantly, the analytical model directly verifies the Gryte-Lovindger ansatz, that the system "selects" a crystal growth rate that matches the sink speed. |
Monday, March 14, 2022 1:18PM - 1:30PM |
B19.00008: Role of stress relaxation in polymer crystallization under fast stretching Wenbing Hu, Wen Luo, Jiping Wang, Yaqian Guo The industrial processings of commercial polymers like fiber spinning, film stretching and plastic molding commonly hold a fast stretching process for crystallization. How the limited stress relaxation during fast stretching plays its role in polymer crystallization remains as unclear. We performed dynamic Monte Carlo simulations of stress-induced polymer crystallization and found that stress relaxation mainly plays a kinetic role rather than the expected thermodynamic role. In comparison to strain-induced polymer crystallization under parallel conditions, the intermolecular relaxation hinders the intramolecular relaxation, and hence retards crystallization upon fast stretching. Furthermore, stress relaxation is enhanced by crystal reorganization in the post-growth stage of polymer crystallization, which influences crystallinity harvest and crystal morphologies. |
Monday, March 14, 2022 1:30PM - 1:42PM |
B19.00009: Disclose atomic interaction at the interface betweenpolyethylene and the edge ofmonolayer two-dimensional materials Bo Li Here we combine an advance synthesis of two-dimensional (2D) materials (MoSe2) having well-defined atomic edge configurations and with ab-initio and atomistic molecular dynamics (MD) simulations to elucidate how atomic edges interact with polyethylene (HDPE) chains in a dilute solution assembly process. Our results reveal that Mo-terminated zigzag (Mo-ZZ) edges act as preferred nucleation sites and strongly interact with HDPE chains. The HDPE chains align in parallel with the Mo-ZZ edges and form arrays of lamellae that are perpendicular to the edges. Interestingly, atomic edge configurations are observed to dramatically change such interactions. The ab-initio calculation and MD simulation suggest that Se-terminated edges have lower binding energy with HDPE chains in comparison to other edges and that they are not expected to be preferred nucleation and lamellae growth sites. The crystallization discrepancy at different edges was demonstrated on the same piece of MoSe2 with different types of edges. Following the Mo-ZZ edge preferred nucleation principle, controlled long-range alignment of HDPE lamellae can be realized by creating multilayer MoSe2 with parallel atomic steps. |
Monday, March 14, 2022 1:42PM - 1:54PM |
B19.00010: Comparison of PA6 and PA66 crystallization using modified FSC Xiaoshi Zhang, Evan Quinn, John Buzinkai, Alicyn Rhoades PA66 and PA6 share many comparable properties due to their similar chemical structures. However, their crystallization kinetics differences are not received similar attention as their other properties. With the advent of the modified FSC, non-damaging spectroscopy and morphology characterization can be performed in addition to the calorimetry analysis. The polymorphs, crystallization kinetics, and morphology of two polyamides are studied in a wide crystallization temperature span. Time-temperature-transformation (TTT) diagrams of PA66 and PA6 are built to compare their crystallization behaviors. It is noted that the crystallization rate of PA66 is always faster than PA6 in the entire crystallization temperature range. The nodular–spherulitic morphology transition takes place at a higher temperature of 135°C in PA66 than 120 °C in PA6. The use of the TTT diagram also successfully predicts the impact of different crystallization pathways on their final morphology. With increasing cooling rate from 10K/s to 3000K/s, both polyamide samples experience gradual morphological changes from spherulitic, spherulitic/nodular, spherulitic/amorphous, and full amorphous. The different morphologies are further investigated by μFTIR and calorimetry analyses. |
Monday, March 14, 2022 1:54PM - 2:06PM |
B19.00011: Crystalline Structure and Thermal Transition of Regioregularity-Controlled Poly(3-dodecylthiophene) Hyeonjung Park, Moon Jong Han, Youngkwon Kim, Eun Ji Kim, Hyeong Jun Kim, Dong Ki Yoon, Bumjoon J Kim We investigate the liquid crystalline (LC) phase transition of regioregularity (RR)-controlled poly(3-dodecylthiophene) (P3DDT). Controlling RR of the P3DDT from 95 to 65% provides significantly altered strength of the LC interactions while maintaining the chemical structures the same. As the RR decreases, the P3DDT exhibits progressively decreased phase transition temperatures under polarized microscopy due to weaker interchain interactions. In the X-ray scattering and thermal analysis, the melting of the side-chain and backbone lead to entering the nematic and isotropic phases, respectively. Furthermore, P3DDTs with high RR exhibit only the Form I crystal structures. However, P3DDTs with low RR adopt both the Form I and Form II crystal structures, where Form II crystals contain interdigitated alkyl side-chain. The amount of Form I crystals is significantly decreased as the RR decreases, and Form II crystals are dominantly observed for RR 60% P3DDT. These features explain the significant decreases in the phases transition temperatures of P3DDTs with lower RR. This study provides an understanding of the RR effect on crystalline structures and thermotropic LC behavior of P3DDTs, allowing for exquisite control over their self-assembly and optoelectrical properties. |
Monday, March 14, 2022 2:06PM - 2:18PM |
B19.00012: Sensing the melting transition of semicrystalline polymers via a novel fluorescence technique Kailong Jin In this study, we have developed a new, simple, and versatile fluorescence technique for probing the melting transitions of semicrystalline thermoplastics. With this approach, fluorescent probes are incorporated into a semicrystalline polymer, either by physical doping or covalent labeling, and their T-dependent fluorescence intensity data exhibit a stepwise decrease nearby Tm because of the reduced restriction of intramolecular motion when crystals start to melt. Interestingly, the first derivative of the obtained T-dependent fluorescence intensity data can reveal more details of the melting transition, e.g., the onset and endset of the melting transition as well as the peak melting temperature. The melting point values determined by fluorescence agree well with those characterized by conventional differential scanning calorimetry. This fluorescence technique can be applied with various types of fluorescent probes and generalized to many semicrystalline thermoplastics, while maintaining excellent sensitivity to melting transitions. Our fluorescence technique represents an easy and contact-free melting point characterization approach that may allow for novel location-specific Tm investigations within heterogeneous polymeric systems (e.g., multilayer films and composites). |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700