Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session A43: Polymer Crystallization from Classical to Functional Systems IFocus
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Sponsoring Units: DPOLY Chair: Toshikazu Miyoshi, Akron Univ Room: LACC 503 |
Monday, March 5, 2018 8:00AM - 8:36AM |
A43.00001: Polymer Crystals and Crystallization: A Rediscovered and Challenging Research Field Invited Speaker: Stephen Cheng
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Monday, March 5, 2018 8:36AM - 8:48AM |
A43.00002: The Role of Co-Units in Polymer Crystallization and Melting: New Insights from Fast Scanning Calorimetry on Poly(ethylene-co-octene) Evgeny Zhuravlev, René Androsch, Vadlamudi Madhavi, Arnold Lustiger, Christoph Schick The effect of noncrystallizable units on the crystallization and melting of polyethylene was studied for three ethylene octene copolymers [1]. Using fast scanning calorimetry (FSC) at cooling rate 100,000 K/s allows isothermal crystallization at 62 °C for all three samples. Heating at 10,000 K/s provides the melting curves of the isothermally formed crystals. At slow DSC cooling rates crystallization is determined by the ethylene sequence length distribution and the melting point of the corresponding crystals depends on crystal thickness [2]. Contrary, for the isothermally at 62 °C crystallized samples of different co-unit content the melting behavior is very similar. Under this particular conditions co-unit content only influences crystallization kinetics but not crystal thickness. |
Monday, March 5, 2018 8:48AM - 9:00AM |
A43.00003: Crystallization of Isotactic Poly(methyl methacrylate) Monolayer Observed by High-Resolution Atomic Force Microscopy in Real Time Yuki Ono, Jiro Kumaki In the early 2000s, the crystallization behaviors of polymer films were successfully visualized by AFM in real time, and the growth of individual lamellae could be analyzed by AFM (Hobbs et al., Macromolecules, 34, 5508 (2001)). However, high-resolution (HR) imaging at the molecular level has not been attained, because relatively thick spin-cast films were used for the observations. |
Monday, March 5, 2018 9:00AM - 9:12AM |
A43.00004: Intramolecular Crystal Nucleation of Polymers Containing Sequence Defects Wenbing Hu, Huacheng Tao, Huanhuan Gao Sequence defects of polymers such as the short branches of polyethylene as well as the stereo-isomers of polypropylene suppress the crystallinity for a broad application from plastics to elastomers. We performed dynamic Monte Carlo simulations of single linear and cyclic polymer chains containing a few of sequence defects. The free energy curves of crystallization/melting show that the sequence defects generally suppress the melting point from homopolymers, but affect little to the kinetic barrier of intramolecular crystal nucleation. In addition, the chain ends play the similar role with the sequence defects in crystallization. Our results shed light onto the microscopic mechanism of sequence-length segregation upon crystallization of statistical copolymers. |
Monday, March 5, 2018 9:12AM - 9:24AM |
A43.00005: Crystallization of Binary Polymer Blends Ashok Dasmahapatra Polymer blends are known to be one of the exciting materials to prepare nanoscale devices via self-assembly. We report dynamic Monte Carlo simulation results on the crystallization of A/B binary polymer blends with varying composition, wherein both the components are crystallizable. We model A-polymer as high melting component and hence its crystallization precedes the crystallization of B-polymer upon cooling from a homogeneous melt. The morphological development is controlled by the interplay between crystallization driving force (attractive) and de-mixing energy (repulsive) between the components. With increasing the composition of B-polymer, macrophase separation, crystallization and lamellar thickness follow a non-monotonic trend. This non-monotonic trend is attributed to the composition-heterogeneity in the blend. When one component is relatively less compared to the other, its mobility is reduced affecting crystalllization temperature. As a result, transition happens at a relatively lower temperature (viz., enhanced thermal driving force). Isothermal crystallization reveals that the crystallization behavior and crystal morphology strongly depends on the mode of cooling. Two-step, compared to on-step isothermal crystallization provides better crystalline structures. |
Monday, March 5, 2018 9:24AM - 9:36AM |
A43.00006: Folding of Semicrystalline Polymer as Functions of Kinetics, Molecular Weight, and Entanglement Shijun Wang, Shichen Yuan, Toshikazu Miyoshi Long polymer chains drastically change their structures from random coils to folded chains. Recent studies using Solid-State NMR spectroscopy and 13C selective isotope labeling enabled one to investigate chain-folding structure of polymer in both solution- and melt-grown crystals as a function of kinetics. In this study, we synthesize various 13C labeled PLLA samples with different molecular weights. In this presentation, it will be for the first time demonstrated that how kinetics, entanglements, and molecular weights affect chain-folding structure of PLLA in bulk and solution-grown crystals. On the basis of chain-level structure, we will discuss about crystallization mechanisms of long polymer chains at the molecular scale. |
Monday, March 5, 2018 9:36AM - 9:48AM |
A43.00007: The Underestimated Effect of Existence or Absence of Intra-Crystalline Chain Dynamics (αc-relaxation) on Morphology and Stability of Semicrystalline Polymers Martha Schulz, Anne Seidlitz, Ricardo Kurz, Kay Saalwaechter, Thomas Thurn-Albrecht Some polymers show translational motion of the chains in crystallites – the αc-relaxation. Although it was recognized early by Boyd that αc-mobile polymers have a higher crystallinity than crystal-fixed polymers, the relaxation process has been ignored in most crystallization models. We show that the αc-relaxation has a strong influence on the crystallization process, changing morphology and stability of the sc structure. Using SAXS, we compare structural characteristics for PEO (αc -mobile) and PCL (crystal-fixed) after isothermal crystallization and during heating. With NMR we can estimate the timescale of the αc-relaxation depending on T. A direct comparison points out fundamental differences: PCL shows marginally stable lamellae with a narrow thickness distribution, starting to reorganize for T> Tc. In contrast, PEO shows a well-defined, narrowly distributed amorphous thickness da and a broad thickness distribution of the lamellae. For T>Tc, the lamellae are stable over a wide range. We hypothesize that due to the αc-relaxation, the lamellae thicken directly behind the growth front up to a minimal da. This is supported by NMR-results: At high Tc the αc-relaxation is fast enough to enable crystal reorganization to take place in a narrow zone directly behind the growth front. |
Monday, March 5, 2018 9:48AM - 10:00AM |
A43.00008: Development of Ultrafast Scanning Calorimetry by the Liquid Drop Enhanced Cooling Method Dongshan Zhou, Evgeny Zhuravlev, Jing Jiang, Bin Yang, Christoph Schick, Shaochuan Luo, Gi Xue Nitrogen or Helium gas as coolant in the ultrafast scanning calorimetry (UFSC) has the advantage of fast shift between programmed heating and cooling, but less effective for fast cooling when the sample temperature is close to the ambient temperature. Here we introduce the method of liquid drop enhanced cooling method that can break through the bottleneck arising from the ballistic cooling problem. We show here that after controlling the drop size, proper heating loop cuting, avoiding of Leidenfrost effect, the cooling rate reaches up to 105 Kelvin per second, i.e., about 4 orders of magnitude faster than cooling by gas at a 50K difference between the sample and the ambient temperature. This method opens even wider windows for the study of various liquid-solid or solid-liquid transformations. |
Monday, March 5, 2018 10:00AM - 10:12AM |
A43.00009: Yield Stress Enhancement in Polyethylene-Glassy Block Copolymers William Mulhearn, Richard Register Polyethylene (PE) has the highest annual production volume of all synthetic polymers, and is broadly employed due to its toughness, processability, chemical resistance, and low cost. However, PE is not suited to certain applications due to its modest yield stress and Young’s modulus, ~30 MPa and ~1 GPa respectively for high-density PE. Irreversible deformation results from dislocation of crystal stems and crystal fragmentation under stress. At room temperature, the liquid-like amorphous layer provides no mechanical support to the crystal surface. The mechanical properties of PE can be modified via incorporation of a short block with a high glass transition temperature into a majority-PE block copolymer. We investigate glassy-PE block copolymers prepared by ring-opening metathesis polymerization of norbornylnorbornene and cyclopentene, followed by hydrogenation. A large change in mechanical behavior can be achieved even at low glassy block content, e.g. doubling the yield stress and Young’s modulus with the addition of ~15 weight percent glassy block (Tg = 115 °C). Property enhancement is closely associated with the composition of the amorphous layer and the spatial distribution of the glassy block. Furthermore, we relate ductility with the presence or absence of tie molecules. |
Monday, March 5, 2018 10:12AM - 10:24AM |
A43.00010: The Impact of Isotopic Substitution on the Crystallization and Melting Behaviors of Selectively Deuterated Poly(ε-caprolactone)s Dongsook Chang, Lengwan Li, Tianyu Li, Jacek Jakowski, Jong Kahk Keum, Peter Bonnesen, Kunlun Hong We have previously shown that material properties of conjugated polymers can be tuned by selective deuteration,1 which is also an important tool for various analytical techniques. Here we investigate the effects of deuteration on the crystallization and melting behaviors of poly(ε-caprolactone) (PCL). Partially and fully deuterated PCLs of matching molar masses are polymerized from novel deuterated monomers. The deuterated PCLs crystallize and melt at lower temperatures with a smaller change in enthalpy than the protonated PCL when measured by calorimetry. Considering that their crystal structure, crystallinity, and lamellar packing are minimally impacted by deuteration, we hypothesize that the observed differences are attributable to weaker intermolecular interactions of the deuterated PCLs. Interestingly, selective deuteration only on the carbons adjacent to the ester group leads to slower crystallization, which could result from the isotopic heterogeneity. Quantum mechanical MD simulations are attempted to analyze the differences in their molecular interactions. |
Monday, March 5, 2018 10:24AM - 10:36AM |
A43.00011: Effect of Particle Grafting on Directing Organization Through Polymer Crystallization Andrew Jimenez, Sanat Kumar, Jacques Jestin It has recently been shown by tuning the crystallization rate of a semicrystalline polymer that grafted nanoparticles (NP) can be forced into interlamellar, interfibrillar, and interspherulitic regions by controlling the isothermal crystallization temperature. Results thus far have demonstrated the ability to tune the fractions of NPs that end up in each region with just temperature. However, crystallization speed and particle mobility are inherently affected by the grafted polymer, used to ensure good initial dispersion in the polymer melt due to the favorable interaction between the graft and matrix. To further study this effect of mobility on the ordering of NPs we vary the graft density of chains on the particle surface, as well as NP size, thereby manipulating their ability to get “pushed” more easily into the various crystal regions. The decrease in effective diameter of these NPs allow for significantly faster crystallization of the surrounding matrix, demonstrated with isothermal DSC experiments. The combination of these effects lead to variations in the NP ordering, as seen with SAXS and TEM. With a variety of nanofillers available, these materials provide a scheme for determining how to optimize the various properties of these trapped-particle composites. |
Monday, March 5, 2018 10:36AM - 10:48AM |
A43.00012: Molecular weight and distribution of crystalline polymers by non-isothermal crystallization kinetics Shuangjun Chen, Limin Wang Tri-block copolymer poly(styrene)-b-poly(ethylene oxide)-b-poly(styrene) (SEOS) and homopolymer poly(ethylene oxide) (PEO) with almost the same molecular weight as PEO block were studied comparatively under non-isothermal conditions on differential scanning calorimetry (DSC) . From final degree of crystalline Xc and given degree of polymerization N, relative degree of crystalline Xt at nucleation stage was changed to be monomer unit numbers involved in crystallization process. Based on well recognized model of PEO crystalline structure, Xt can be used to calculate the scales of PEO crystalline. These results indicate that the degree of polymerization can be calculated by DSC. By using two type of polypropylene (PP) of industrial grade as model polymers, we present and corfirm a novel method to test the molecular weight and distribution of crystalline polymers through non-isothermal crystallization kinetics from cooling and heating curves. The method is low cost,easy and environmental due to lack of solvent. |
Monday, March 5, 2018 10:48AM - 11:00AM |
A43.00013: Monte Carlo Simulations of Stress Relaxation in Polymer Stretching Jiping Wang, Wenbing Hu Industrial polymer processing such as fiber spinning, plastic molding, film stretching and film blowing are commonly performing stretching with stress relaxation. In the previous Monte Carlo simulations on strain-induced polymer crystallization [1-3], we have developed a scheme to stretch the polymers in a network without any stress relaxation. Here a proper stress relaxation on the basis of Brownian motions of polymer chains is incorporated into this stretching process. The results demonstrated the Debye-type stress relaxation behaviors, and the Arrhenius-type temperature dependence of their characteristic relaxation times. The new scheme allows us to further investigate how the stress relaxation influencing polymer crystallization during stretching, and thus understand better the microscopic mechanism of polymer processing. |
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