Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session R55: Polymer Crystallization II: Packing Assembly, Chip Calorimetry and SimulationsFocus
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Sponsoring Units: DPOLY Chair: Claudio De Rosa, University of Naples Federico II Rufina Alamo, Florida A&M and Florida State University Room: BCEC 254B |
Thursday, March 7, 2019 8:00AM - 8:36AM |
R55.00001: Isodimorphic biodegradable copolyesters: Structure and crystallization behavior Invited Speaker: Alejandro J. Müller Random copolymers with crystallizable components can crystallize in three modes: (a) comonomer exclusion, in which the comonomer is excluded from the crystal lattice of the other component, (b) isomorphism (i.e., strict molecular requirements should be met), in which a single crystalline phase is observed for all compositions, because of comonomer inclusion, and (c) isodimorphism, where two crystalline phases are formed depending on the composition, and both phases allow comonomer inclusion. In the present invited lecture, the detailed structure, morphology, nucleation and crystallization behavior of isodimorphic biodegradable copolyesters will be presented as a function of their comonomer ratio. This information is very significant as it allows tailoring the properties of random copolymers as well as their applications. The materials exhibit a pseudo-eutectic type phase behavior. To the left and to the right of the pseudo-eutectic a single phase is formed, rich in the corresponding parent comonomer. However, near the pseudo-eutectic point, two crystalline phases can be formed. In this way, double crystalline materials with interesting spherulitic superstructures that contain both types of lamellar thickness can be generated. The applications of these materials are potentially very interesting as superstructures with different sensitivities to biodegradation could be prepared and their lifetime can be tailored from their structural characteristics. |
Thursday, March 7, 2019 8:36AM - 8:48AM |
R55.00002: Packing Selection of a Helical Semicrystalline Polymer in Solution and Melt-Grown Crystals Toshikazu Miyoshi Correlation between packing and chain-folding structures of semicrystalloine polymers has not been clearly addressed in existing literature. We investigate kinetics effects on chain packing as well as chain-folding structure of a helical chiral polymer in solution- and melt-grown crystals. We will provide a novel concept of intramolecular and intermolecular packing to understand kinetics effects on packing selection in the melt and solution-grown crystals. |
Thursday, March 7, 2019 8:48AM - 9:00AM |
R55.00003: Semicrystalline polyethylene measurement by Polarized Resonant Soft X-ray Scattering Dean DeLongchamp, Eliot H Gann, Chad Ray Snyder Orientation and conformation in nanoscale amorphous regions often dominates the properties of soft materials such as composites and semicrystalline polymers. In polyethylene (PE), interlamellar amorphous tie chains have been shown to substantially reduce the rate of slow crack growth, which is important for long service life in infrastructure elements such as potable water pipes. I will describe polarized resonant soft X-ray scattering (P-RSoXS) measurements of semicrystalline polyethylenes. The P-RSoXS of PE is highly anisotropic with respect to electric field vector and orientation of the amorphous interlamellar chains is a significant contributor. Real space models reproduce salient features of the P-RSoXS pattern including trends in anisotropy with energy, trends in anisotropy with q, and a clear long period peak. Prospects for correlating interlamellar orientation measurements by P-RSoXS with tie chain population and crack growth will be discussed. |
Thursday, March 7, 2019 9:00AM - 9:12AM |
R55.00004: Polymorphism in nanolayered comb-like and linear precision polymers Varun Danke, Gaurav Kumar Gupta, Mario Beiner Comb-like polymers with rigid backbones and flexible alkyl side chains are a class of functional materials which often exhibit long range ordered states wherein main and side chains form an alternating layered arrangement on length scales of 1-3 nm. Similarly, linear precision polymers synthesized by ADMET polymerization, incorporating ring-like units placed at regular intervals along a polyethylene backbone also typically show nanolayered structures[1]. Here we present results of a comparative study using X-ray scattering and calorimetry highlighting similarities and differences in structure formation in these two material classes. Of special interest is the competition of the individual packing tendencies of rings and methylene sub-units that drive polymorphic behavior which is a commonly encountered phenomenon in such nanolayered systems. The role of substrates and interfaces on their crystallization behavior is also briefly discussed. |
Thursday, March 7, 2019 9:12AM - 9:24AM |
R55.00005: Unusual crystallization kinetics of long-spaced polyacetals Xiaoshi Zhang, Sidney Cameron, Rufina Alamo, Xiaobin Zuo, Patrick Ortmann, Stefan Mecking The overall crystallization kinetics of the major polymorphs of a series of polyethylenes with acetal groups precisely placed on each and every 12th, 18th, 19thand 23rdbackbone carbon (PA-12, PA-18, PA-19, and PA-23) have been studied by DSC and FSC with parallel studies using FTIR, real-time X-ray and POM. The crystallization kinetics is unusual because multiple minima of isothermal crystallization rates are observed at polymorphic transition temperature regions, which is reminiscent of previous observations of crystallization minima in precision polyethylenes with halogen. The inversion is mainly associated with a confinement effect that the kinetically favored Form I makes on the growth of the more stable Form II. Besides the effect on growth, data of induction time for crystallization indicates that the presence of Form I also retards the nucleation of Form II. |
Thursday, March 7, 2019 9:24AM - 9:36AM |
R55.00006: Homogeneous crystal nucleation in polymers: New insights from fast scanning calorimetry Evgeny Zhuravlev, Rene Androsch, Ruslan Andrianov, Christoph Schick Crystallization commonly starts from a (sub)nanoscale nucleus which eventually growth to a crystal. Classical nucleation theory (CNT) provides a qualitative description of these processes. Homogeneous nucleation, to become dominat over heterogeneous nucleation, requires deep undercooling of the polymer melt. At cooling rates of several thousand K/s such states can be reached and the kinetics of homogeneous nucleation becomes accessible. Fast scanning calorimetry (FSC), in combination with polarized optical (POM) and atomic force (AFM) microscopy, provides a tool to study homogeneous nucleation and even the thermodynamic stability of the formed nuclei as fuction of nucleation temperature and time. |
Thursday, March 7, 2019 9:36AM - 9:48AM |
R55.00007: Using chip-based calorimetry to monitor crystallization during polymer processing Kenneth Kearns, Thomas R Fielitz, Rajen M Patel, Shrikant Dhodapkar, Travis McIntire, Jin Wang, Christopher M Thurber, Robbyn Prange Polymer processing often involves rapid changes in temperature and strain, which significantly modify the properties and thus performance. Advancements in chip-based calorimetric techniques overcome temperature scanning rate and instrument response limitations of conventional differential scanning calorimeters, enabling off-line probing of commercially relevant process conditions. In this talk we will describe how we have used commercial, chip-based calorimetric instrumentation to monitor crystallization under process relevant conditions. Using a chip-based calorimeter we can monitor the crystallization of semi-crystalline polyolefins as they move through the pelletization step of the manufacturing process. Mapping time-dependent crystallization covering up to 1000 seconds was possible. Blown film processing, which undergoes cooling at rates approaching 100 ○C/s, could be mimicked using the chip calorimeters. By coupling this data to at-line monitoring schemes, strain-induced crystallization can be deduced. |
Thursday, March 7, 2019 9:48AM - 10:00AM |
R55.00008: Visualization of Polymer Crystallization by a Combination of Atomic Force Microscopy with Fast Scanning Calorimetry Rui Zhang, Evgeny Zhuravlev, Christoph Schick Abstract: The chip-sensor of fast scanning calorimetry (FSC) is directly mounted on the scanner of an atomic force microscope (AFM). By combining AFM with FSC (AFM-FSC) this way, AFM can illustrate the crystal structures on the nanoscale, as well as, FSC can treat the sample at any annealing temperature without unexcepted crystallization during heating or cooling at scanning rates up to 1,000,000 K/s. First results on crystals’ morphologies, spherulites’ growth rates and the influence of crystal nuclei by Tammann’s two stage method are shown. |
Thursday, March 7, 2019 10:00AM - 10:12AM |
R55.00009: Slip-link modeling of a crystallizing entangled polymer melt Marat Andreev, Gregory C Rutledge Modeling of polymer processing is a subject of continuing industrial and theoretical interest. Many industrial polymer melts are entangled and undergo crystallization during processing. Experimental data for the rheology of crystallizing entangled polymers are available in a number of published studies on this topic. In particular, the ``inverse quench'' technique allows one to stop crystallization in effect, and to measure the dynamic modulus over a wide range of frequencies. Meanwhile, over the past few years, slip-link models have been demonstrated to be very capable for describing the rheology of entangled melts. In this work, we present a modification of the slip-link model to capture the rheology of an entangled melt during the early stages of crystallization. The model captures the emergence of a secondary, low-frequency plateau observed in the linear regime. The advantage of this approach is the capability to predict the effect of on-going crystallization during non-linear deformation. |
Thursday, March 7, 2019 10:12AM - 10:24AM |
R55.00010: Monte Carlo simulations of stress-induced polymer crystallization Wenbing Hu, Jiping Wang We developed the previous approach of dynamic Monte Carlo simulations of bulk lattice polymers for strain-induced crystallization [1-3] by incorporating the stress relaxation, and investigated the competition between strain rate and stress relaxation rate. The results reproduce the basic experimental observations and promise a molecular-level understanding of stress-induced polymer crystallization via our new approach. |
Thursday, March 7, 2019 10:24AM - 10:36AM |
R55.00011: Monte Carlo Simulation of Stress-Induced Polymer Crystallization during Cold Drawing Jiping Wang, Yihuan Yu, Wenbing Hu Jiping Wang, Yihuan Yu, Wenbing Hu* |
Thursday, March 7, 2019 10:36AM - 10:48AM |
R55.00012: Polymer Crystallization during shear flow Go Matsuba We evaluated the effect of molecular weight on the formation of a shish–kebab morphology on a wide spatial scale. Here we examined blended polyethylene with 97 wt% deuterated polyethylene and 3 wt% protonated polyethylene comprising molecules with a range of molecular weights. Measurements were conducted with various X-ray and neutron scattering techniques. The nanometer-scale analysis revealed that the crystal lattice is also independent of the molecular weight. Moreover, small-angle X-ray and neutron scattering measurements did not reveal any influence of molecular weight. On the other hands, strong streak-like neutron scattering was observed perpendicular to the drawing direction. The multicore-shell cylinder model was used to evaluate the parameters of the shish structure: the radius of the core cylinders increased with the molecular weight while the number of core cylinders decreased with the molecular weight. On the other hand, the micron-scale analysis using ultra-small-angle X-ray and neutron scattering measurements revealed that the micrometer-scale fibril structure is independent of the molecular weight. |
Thursday, March 7, 2019 10:48AM - 11:00AM |
R55.00013: Modeling the melting of a semicrystalline polymer Kiran Iyer, Marzbed Margossian, Murugappan Muthukumar The melt state of a semicrystalline polymer is known to have several dependencies on process variables such as melt temperature and annealing time; it is by itself a rich system, possibly consisting of several topological constraints like entanglements. All of these contribute towards the mechanism of melting, resulting in several intriguing observations in experiments. In this work, we study the melting of a pre-formed polymer crystal by use of coarse-grained parallel tempering Langevin dynamics simulations, guided by experimental findings of the melting of a single polyethylene crystal. By investigating the melting of a single crystal, we determine the kinetics of the process. We also determine the kinetics of an aggregate formed by multiple polymer chains, and find that the kinetics is dependent on the polymer chains being able to cross an entropic barrier. |
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