Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session U32: Polymers with Special Architectures: From Molecular Design to Physical Properties IFocus
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Sponsoring Units: DPOLY DSOFT Chair: Reika Katsumata, Univ of Mass - Amherst Room: 504 |
Thursday, March 5, 2020 2:30PM - 2:42PM |
U32.00001: Effect of Molecular Architecture on the Conformational Relaxation for Interfacial Polymer Chains Hung K. Nguyen, Daisuke Kawaguchi, Keiji Tanaka Conformational relaxation processes of polymer chains trapped in a metastable state in close proximity to a solid interface can strongly affect the physical properties of polymer nanocomposites. Using sum-frequency generation spectroscopy, we here report the thermal annealing effect on chain conformations of polystyrene (PS) with different molecular architecture near at the quartz interface. Relaxation dynamics for PS chains strongly adsorbed at the outermost substrate interface and those located next to the adsorbed layer were characterized. PS chains exhibited much slower relaxation dynamics with a star-shaped architecture than with a linear one. This finding is in consistent with a scenario that the entropic interaction with the solid surface is stronger for a star-shaped macromolecule than for a linear one. |
Thursday, March 5, 2020 2:42PM - 2:54PM |
U32.00002: In Situ Synchrotron Radiation X-ray Scattering Evaluation of Domain Size and Spacing of Thermoplastic Elastomer under Elongation Nattanee Dechnarong, Kazutaka Kamitani, Chao-Hung Cheng, Shiori Masuda, Shuhei Nozaki, Chigusa Nagano, Yoshifumi Amamoto, Ken Kojio, Atsushi Takahara Microphase separation occurs in polystyrene (PS)-b-poly(ethylene-co-butylene)-b-PS (SEBS), leading PS domains to serve as physical crosslinking points. To improve mechanical strength of SEBS, mechanical stability of PS needs to be clarified. Here, the molecular aggregation structure of SEBS films containing spherical PS domains packed in b.c.c. lattice was measured during stretching using in situ SAXS. During uniaxial stretching, a shift of structure factor reveals an increase in domain spacing in parallel to stretching direction while it decreased in the perpendicular direction. Affine deformation of all diffraction planes was observed, while they deviated from the trend above strain 5 equally. In the case of biaxial stretching, an increase in the domain spacing was observed in both stretching directions, indicating an isotropic deformation. Deviation from affine deformation of each diffraction plane was observed above strain 1.5, referring to the difficulty of maintaining the paracrystalline structures during biaxial stretching. Domain size of PS domains with polydispersity was determined from form factor using model calculation. From the change of radius, PS domains were proposed to deform to prolate and oblate spheroids during uniaxial and biaxial elongation, respectively. |
Thursday, March 5, 2020 2:54PM - 3:06PM |
U32.00003: Structure and Physical Properteis of Zwitter Ionic Polyelectrolyte Brushes at Aquesous Interface Atsushi Takahara Polymers chemically grafted to the surface of substrates are typical soft interfaces known as polymer brushes. Surfaces covered with polyelectrolyte brushes are attractive because of their potential applications including adhesion, antifouling, biocompatibility and water lubrication systems. In this presentation, our recent researches on control of wettability and adhesion through precise design of polyelectrolyte brush surfaces are presented. We started from fundamental science including precise polyelectrolyte synthesis and solution characterization of polyelectrolytes, characterization of polymer brush at water interfaces, and water structure in polymer brushes. On the basis of these fundamental studies, we have achieved 1) superhydrophilicity, 2) antifouling properties, 3) super-lubricant behavior, 4)intelligent adhesion and 5) cell-surface interaction control. |
Thursday, March 5, 2020 3:06PM - 3:18PM |
U32.00004: Highly Branched Polymers with High Ether Oxygen Content for Membrane CO2/N2 Separation Haiqing Lin Membrane technology has emerged as a potentially economically viable alternative for CO2 captures from fossil fuel-fired powers, enabled by advanced membrane materials with high CO2 permeability and high CO2/N2 selectivity. Current leading membrane materials usually contain poly(ethylene oxide) (PEO) because the ether oxygen in PEO interacts favorably with CO2, resulting in high CO2/N2 selectivity. Herein we prepare a series of highly branched amorphous polymers containing poly(1,3-dioxolane), which has an O:C ratio of 0.67, higher than 0.5 in PEO. The length of the poly(1,3-dioxolane)-based branches are tuned to yield amorphous nature, and mobile ethoxyl chain end groups are introduced to provide high free volume and gas diffusivity. These ether oxygen-rich polymers exhibit more superior CO2/N2 separation properties than the PEO-based materials at practical conditions for flue gas processing, and above the Robeson’s upper bound. This work demonstrates that harnessing the interactions between polymers and CO2 may provide unprecedented opportunities in designing gas separation membranes with robust performance under practical conditions. |
Thursday, March 5, 2020 3:18PM - 3:30PM |
U32.00005: Protein Resistant Property of Nanometer-Scale Architecture of Polymer Chains Maya Endoh, Daniel Salatto, Zhixing Huang, Yuto Koga, Yashasvi Bajaj, Benjamin Yavitt, Jan-Michael Carrillo, Dmytro Nykypanchuk, Tad Koga We recently reported that a few nanometer-thick polymer layer formed on a solid, which consists of physisorbed non-charged homopolymer chains, exhibits anti-fouling properties against a model protein, bovine serum albumin (BSA), independent of polymer hydrophilicity/hydrophobicity[1]. We revealed that the highly packed chain architecture plays a crucial role in its protein resistant property over surface chemistry. Here, we further illuminate how this nanometer-scale chain structure impacts the protein adsorption on ultrathin polymer films. Polymer films with different thicknesses ranging from 2 nm to 200 nm of polystyrene, poly(2-vinyl pyridine), polybutadiene, poly(methyl methacrylate), and polypropylene were prepared. Adsorption of fluorescein labeled BSA and fibrinogen on these thin films were studied as a function of film thickness using photon counting spectrofluorometry. We observe that the critical thickness of the adsorption transition from anti-fouling to fouling appeared irrespective of the type of polymers and proteins. In addition, molecular dynamics simulations were performed to mimic the protein adsorption process. We will discuss the mechanism behind the phenomenon. |
Thursday, March 5, 2020 3:30PM - 3:42PM |
U32.00006: Linear vs Star polymers in Hydrogen-Bonded Assemblies Aliaksei Aliakseyeu, John F Ankner, Svetlana Sukhishvili We report on the effect of the molecular architecture of poly(ethylene oxide), PEO (linear vs. 6-arm polymer, lPEO and sPEO, respectively) and molecular weight of poly(methacrylic acid) (PMAA) on hydrogen-bonding assembly of these polymers. Isothermal titration calorimetry studies (ITC) revealed the entropic nature of complex formation and complex strengthening with the increase of molecular weight of PMAA. At the same time, lPEO-containing and sPEO-containing complexes had a different stoichiometry of PMAA-to-PEO repeat units of 1 and 1.5 for PMAA/lPEO and PMAA/sPEO, respectively, suggesting possible formation of necklace-like complexes on a PMAA string. When the assembly was performed at surfaces, layer-by-layer (LbL) PMAA/PEO films constructed with linear PEO exhibited faster deposition of polymer mass as compared to films built with sPEO. Consistent with these results, neutron reflectometry revealed stronger molecular intermixing within films containing lPEO, suggesting faster diffusion of lPEO in LbL films as compared to the necklace-included sPEO polymer. |
Thursday, March 5, 2020 3:42PM - 4:18PM |
U32.00007: Effect of Branches and Cycles on Polymer Melt Surface Dynamics Invited Speaker: Mark Foster
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Thursday, March 5, 2020 4:18PM - 4:30PM |
U32.00008: Dilute solution structure of bottlebrush polymers Sarit Dutta, Tianyuan Pan, Matthew Aaron Wade, Dylan J Walsh, Simon A Rogers, Damien S Guironnet, Charles Sing Bottlebrush polymers are the canonical example of hyperbranched polymers, |
Thursday, March 5, 2020 4:30PM - 4:42PM |
U32.00009: Morphology and Dynamics of Catenanes in Dilute Solutions and at Liquid/Liquid Interface Saeed Akbari, Shaghayegh Khani, Joao M Maia, Mesfin Tsige Molecular Dynamics simulations are performed with all-atom poly (ethylene oxide) (PEO) and polystyrene (PS) structures in water and in toluene and at the water/toluene interface and the dynamics and structural properties of PEO and PS chains with different topologies such as linear, isolated rings and interlocked rings (homo and hetero catenation) are studied. This includes the comprehensive study of the effect of chain flexibility, solvent quality and interface as deterministic factors that influence the morphology and dynamics of the catenanes. The results can be exploited to design and fabricate molecules with desired dynamics and will be of particular significance for drug delivery applications. Our simulations predict larger radius of gyration and faster dynamics for flexible topologies in a good solvent. In a poor solvent, they shrink to smaller size and again diffuse faster compared to the rigid counterparts. Moreover, hydrogen bonding significantly affects the dynamics of the molecules in water both in bulk and at the interface. At the water/toluene interface, molecules develop a flat morphology and thus have larger size as compared to their coil structures in the bulk of a good solvent and are found to show faster diffusion. |
Thursday, March 5, 2020 4:42PM - 4:54PM |
U32.00010: Bottlebrush Polymers in the Melt and Polyelectrolytes in Solution Share Common Structural Features Joel Sarapas, Tyler Martin, Alexandros Chremos, Jack Douglas, Kathryn Beers Uncharged bottlebrush polymer melts and highly charged polyelectrolytes in solution exhibit correlation peaks in scattering measurements and simulations. Given the striking superficial similarities of these scattering features, there may be a deeper structural interrelationship in these chemically different classes of materials. Correspondingly, we constructed a library of isotopically labeled bottlebrush molecules and measured the bottlebrush correlation peak position q* = 2π /ξ by neutron scattering and simulations. We find that the correlation length scales with the backbone concentration, ξ ~ cBB−0.47, in striking accord with the scaling of ξ with polymer concentration cp in semi-dilute polyelectrolyte solutions ( ξ ~ cp−1/2 ). The bottlebrush correlation peak broadens with decreasing grafting density, similar to increasing salt concentration in polyelectrolyte solutions. ξ also scales with sidechain length to a power in the range of 0.35 to 0.44, suggesting that the sidechains are relatively collapsed in comparison to the bristle-like configurations often imagined for bottlebrush polymers. |
Thursday, March 5, 2020 4:54PM - 5:30PM |
U32.00011: Effect of Chain Architecture on the Structure, Diffusion, and Swelling in Thin Polymer Films Invited Speaker: Bulent Akgun Polymers with special architectures are utilized in wide variety of technologies such as in pressure sensitive adhesives, biomedical coatings, photoresists, targeting multi-drug resistant gram-negative bacteria, and electrochromic displays. Being able to control the chain architecture opens new pathways to tune physical properties of the polymer thin films through alterations in the entropic contribution. In this work, we have investigated the role of chain architecture on the adsorption, diffusion and swelling in supercritical carbon dioxide (ScCO2) using well-defined linear, star, centipede and comb polystyrene (PS). Structure of irreversibly adsorbed layers are determined using ellipsometry and X-ray reflectivity. Vertical diffusion in bilayer films and ScCO2 swelling in single layer films were determined using in-situ neutron reflectivity measurements. Our results indicated that the normalized equilibrium thickness of the adsorbed layer increases as the number of branches increases and the length of the branches decreases. Independent of the architecture the films are consistently fit using a single layer of uniform density. For the same total molecular weight, thin films composed of more branched polymers have larger diffusion constants than that are made of linear chains. Increase in the fraction of adsorbed chains in a thin film causes a decrease in the vertical diffusion and ScCO2 swelling. |
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