Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session K49: Polymer Networks, Gels, and Elastomers II: Charges & Applications |
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Sponsoring Units: DPOLY Chair: Mehdi Zanjani, Miami University Room: BCEC 252A |
Wednesday, March 6, 2019 8:00AM - 8:12AM |
K49.00001: Impact of Antifoam on Rheological Properties of Polynorborene Membranes for Biobutanol Separation Siyuan Li, Bryan Vogt Butanol is a promising alternative to ethanol for bio-based fuel, but its efficient separation from the fermentation broth can be challenging. Poly(butylnorbornene-ran-hydroxyhexafluoroisopropyl norbornene) (BuNB-r-HFANB) is promising for butanol separation from water. Here, we seek to understand how additives in typical fermentation broths interact with this polymer. The sorption of Antifoam 204 in butanol-water solutions in BuNB-r-HFANB films was characterized by quartz crystal microbalance with dissipation (QCM-D). From the QCM-D data, the dependence of concentration on swelling ratio and rheological properties (complex shear modulus and phase angle) of the films was elucidated. By examination of different film thicknesses, it was determined that the antifoam is incorporated within the film. At 100 ppm of antifoam, the swelling ratio increases by a factor of 170, while the phase angle increases to ~90° (liquid-like). The swelling is nearly unchanged at 10 ppm, but decreases markedly at 1 ppm. This suggests that the polymer is saturated by the antifoam even when only present at 10 ppm. These results illustrate the potential impact of dilute additives on new polymers for pervaporation membranes. |
Wednesday, March 6, 2019 8:12AM - 8:24AM |
K49.00002: The effect of filler distribution in the enhancement of the energy storage in nanocomposites Elshad Allahyarov, Lei Zhu, Guoqiang Zhang Mixing dielectric polymers with high permittivity nano-sized inclusions affects their electrical properties. These nanocomposites are extensively used in actuation applications via employing electrostriction properties of the matrix, and in electrostatic energy storage applications employing high polarization fields of the fillers. In both cases existing theoretical studies mostly utilize mixing rule approaches that consider a homogeneous filler distribution in the matrix. Consequently, the effective permittivity of the composite never exceeds the the permittivity of the filler. We show that much higher effective permittivities can be achieved by manipulating the morphology of the inclusion distribution in the matrix. Simulation results for the field distribution reveal an enhancement of the field localization and dipole-dipole correlation effects in some proposed morphologies. By considering several possible clustering scenarios we found that a cylindrical clustering along the applied field has a potential to achieve an order of magnitude increase in the effective permittivity. The issue of chained filler configurations which lower the breakdown field threshold for the material is also addressed. |
Wednesday, March 6, 2019 8:24AM - 8:36AM |
K49.00003: Analyses of hierarchical structures in vulcanized SBR rubber by using contrast variation USANS and SANS Yuki Watanabe, Mikihito Takenaka, Shotaro Nishitsuji, Satoshi Koizumi, Daisuke Yamaguchi The hierarchical structures of poly(styrene-ran-butadiene) (SBR) rubbers vulcanized with sulfur in swollen state were investigated by using ultra small angle neutron scattering (USANS) and small angle neutron scattering (SANS) technique. The scattering intensity can be described by the equation consisting of two Debye-Bueche equations and Ornstein-Zernike-Debye equation indicating that the inhomogeneous structure with the size of 500 to 900 Å exits, in addition to the inhomogeneous structures with the size of 70 to 100 Å with the networks. As the results of the analyses of contrast variation USANS and SANS, The origin of the inhomogeneous structures with the size of 500 to 900 Å was found to consist of ZnO added as activator of sulfur vulcanization, and we was able to yield the size of ZnO being in the order of 1000 Å quantitatively from the partial structure factor of ZnO. |
Wednesday, March 6, 2019 8:36AM - 8:48AM |
K49.00004: Assignment of the Polymerization Peak in Polystyrene Melt He Cheng, taisen zuo, guisheng jiao, zehua han, junpeng zhao Polymerization peak at around 0.75 Å-1 in polystyrene (PS) melt was first reported by Katz in 1927, it is origin is still not clear. Here, by combined neutron total scattering, high concentration labelling and molecular dynamic simulation, we visualize the most-probable all-atom positions in polystyrene melt, and assign it to be the inter-chain backbone distance. In our experiments, both the neutron and x-ray total scattering profiles from 0.02 to 30 Å-1 of PS-h8, PS-d8, PS-d5 and their mixtures (1:1 by molar) at different temperatures above their glass transition temperatures were measured. The low q scattering profiles in high concentration labelling mixtures are from the thermo fluctuations, while the intermediate and high q scattering profiles are assigned to the inter- and intra- chain atom-atom correlations. |
Wednesday, March 6, 2019 8:48AM - 9:00AM |
K49.00005: Dynamics of Belousov Zhabotinsky Reaction Based Systems Via Nonlinear Stability Analyses Vandana Rajput, Pratyush Dayal Controlling the dynamics of self-oscillating dynamical systems that are far from equilibrium has been a grand challenge for science and engineering. Belousov Zhabotinsky (BZ) reactions, a nonlinear chemical oscillator, has been used to design intrinsically powered self-oscillating dynamical systems. It has been known that the chemical oscillations in BZ reactions are due to the occurrence of Hopf bifurcation (HB). Here, reagent concentrations in the BZ system have been treated as the bifurcation parameter and we perform stability analyses to characterize the dynamics of the BZ system. Specifically, we calculate the first Lyapanov exponent to distinguish quantitatively between the subcritical and supercritical HB. In addition, we also calculate the second Lyapanov exponent to show that for a narrow range of bifurcation parameter, the sustained oscillations in the BZ system transforms in decayed oscillations with sensitive dependence on the initial condition. The transformation of this behavior occurs below a curve called Limit Point of Cycles which is a characteristic of Bautin bifurcation. The outcomes of our study can be utilized to characterize the behavior of dynamical systems and establish design rules for controlling their behavior. |
Wednesday, March 6, 2019 9:00AM - 9:12AM |
K49.00006: Directional Motion of Sodium Polyacrylate Gels Initiated by Ca2+-Induced Contraction is coupled to an NaCl Gradient Susan Kozawa, Loren Kreider, Anita Venkataswamy, Anne Walker, Gary Wnek It is known that Na-polyacrylate gel threads contract in the presence of CaCl2 but we have rather unexpectedly, initiate contraction at or very near the gap, rather than from the side immersed in CaCl2 while the other side is immersed in NaCl. The main mechanism for ion transport initiates through diffusion; the lowest crosslinked gel allows for bulk diffusion while the higher crosslinked gels primarily propagate surface diffusion. Through surface diffusion, the binding mechanism propagates in a linear fashion, from the CaCl2 towards the NaCl. The more interesting phenomena, the bulk diffusion, allows the ion gradients to meet within the middle of the gel. We propose this allows time for the chains to condense in the presence of NaCl, which allows for the entropically favored binding to Ca2+, immediately collapsing chains and allowing the facilitated binding down either end of the gel. Due to this, we are able to induce overall movement of the gel thread. While the phenomena is correlated to diffusion, the rates are mainly determined by polyelectrolyte dynamics. In all cases, original gel dimensions can be recovered upon treatment with chelators such as sodium triphosphate, an analog to ATP. |
Wednesday, March 6, 2019 9:12AM - 9:24AM |
K49.00007: Multiscale investigation of polyelectrolyte gel-based electronic devices Vasilii Triandafilidi, Joerg Rottler, Savvas Hatzikiriakos Gel-based electronic devices (sensors and diodes) are attracting attention due to their low cost, favorable mechanical properties, and biocompatibility. We have performed coarse-grained molecular dynamics and continuum simulations of model polyelectrolyte gels used in such devices to study the relationship between voltage and ion distribution on the nanoscale. For sensors, we consider a system consisting of a negatively charged backbone and positive floating counterions. By interfacing two regions with different degree of ionizations, we compute the electrostatic potential difference and show that it obeys a modified Nernst-Donnan equation when accounted for counterion condensation [1]. The pressure is found to be proportional to the Donnan-Potential, which provides a molecular basis for the piezoionic effect observed in experiments. For gel-based diodes, we interface two gels with oppositely charged ions, study its rectifying behavior with molecular simulations and challenge the results obtained through a description based on the Poisson-Boltzmann approximation. |
Wednesday, March 6, 2019 9:24AM - 9:36AM |
K49.00008: Change in Hierarchical Structure of Segmented Polyurethane Elastomers under Mechanical Deformation Ken Kojio, Chigusa Nagano, Shiori Masuda, Chao-Hung Cheng, Shuhei Nozaki, Kazutaka Kamitani, Atsushi Takahara Polymer materials possess a hierarchical structure such as orientation, conformation, crystal structure, microdomain structure, and so on. When external stimulus is applied to polymers, these various structures would respond depending on the size. In this study, lattice strains obtained from the crystal structure of hard segment domain and microphase-separated structure of segmented polyurethane (SPU) elastomers were evaluated under mechanical deformation by wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) measurements. SPU elastomers were synthesized with poly(oxytetramethylene) glycol, trans-1,4-bis(isocyanatomethyl) cyclohexane (1,4-H6XDI), and 1,4-butanediol. Change in molecular aggregation structure of the SPU with 20 and 30 wt% hard segment contents were investigated. Both strains (eSAXS and eWAXD) obtained from SAXS and WAXD linearly increased with increasing strain. Compared to HX-20, HX-30 exhibited larger eSAXS and eWAXD in both deformation modes. This is because strain can be easily propagated to whole samples due to well-developed hard segment domains formed in HX-30. eSAXS and eWAXD values obtained by biaxial deformation were larger than for uniaxial one, indicating that the biaxial deformation produces severer condition to the samples. |
Wednesday, March 6, 2019 9:36AM - 9:48AM |
K49.00009: Thermal analysis of fully zwitterionic copolymers for safer electrochemical energy storage Andrew Clark, Morgan E Taylor, Matthew J Panzer, Peggy Cebe Current ionic liquid electrolytes used in lithium ion batteries are both volatile and flammable. A safer alternative to liquid electrolytes is to use solid conductive polymer gel electrolytes. In this study, the thermal properties of a group of zwitterionic copolymers designed for electrochemical energy storage are investigated using temperature modulated differential scanning calorimetry (TMDSC) and thermogravimetry (TG). Investigating the thermal properties will reveal how the zwitterionic moieties can affect transition phenomena. Sulfobetaine vinylimidazole (SBVI) and 2-methacryloyloxyethyl phosphorylcholine (MPC) were dissolved in an ionic liquid solution in varying molar ratios and subsequently polymerized to produce fully zwitterionic random copolymers. TG reveals two degradation steps at 290 oC and 390 oC due to MPC degradation and one step at 350 oC due to SBVI degradation. TMDSC at 5 oC/min was used to identify the glass transition of these materials, showing a decrease in Tg from 60 oC to -35 oC with increasing addition of SBVI. A melting endotherm at -18 oC was observed on heating, attributed to the presence of residual ionic liquid. |
Wednesday, March 6, 2019 9:48AM - 10:00AM |
K49.00010: DFT studies of the structural, electronic, and electrochemical properties of copolymers containing ferrocene and imidazole Benjamin Tayo, Eric Mullins Ferrocene-based polymers have been used in various applications such as sensors, solar cells, batteries, and photo-oxidation of thin films. Copolymers containing ferrocene and imidazole are unique because of electronic interactions between the ferrocene and neighboring imidazole moiety, leading to the formation of charge transfer complexes in the polymer. Recent electrochemical and UV-Vis studies in the presence of various electrolytes containing metal ions have revealed significant modifications in their properties, e.g., red shifts, and the appearance of multiple oxidation waves in cyclic voltammetry studies. Even though these modifications have been attributed to the ability of the imidazole to coordinate with metal ions, increasing its electron deficiency, thereby enhancing oxidization of the nearby ferrocene moiety if it is in close proximity to it, the equilibrium geometry of the polymer complex is unknown. This talk will discuss the results of DFT studies that was used to address these concerns, for instance determination of equilibrium geometry, and frontier energy levels. We will also discuss the correlation of molecular orbital density plots to the electrochemical properties, specifically the formation of donor-acceptor complexes within the polymer. |
Wednesday, March 6, 2019 10:00AM - 10:12AM |
K49.00011: Viscoelastic Phase Separation as a Route towards Continuously Processed Organic Solar Cells Jing He, Dilhan M Kalyon, Stephanie S Lee Controlling the solution structure of polymer nanocomposite systems prior to thin film deposition is a promising strategy to enhance the efficiency of organic solar cells in a manner compatible with continuous processing methods. Using a model system comprising P3HT and PCBM dissolved in o-DCB, rheological characterization was employed to characterize the thermoreversible gelation of these solutions upon rapid cooling to sub-ambient temperatures. Temperature-variable confocal microscopy imaging of P3HT fluorescence revealed the formation of micron-sized solvent “holes” during cooling, a signature of viscoelastic phase separation. This phenomenon originates from the dynamic asymmetry between the polymer chains and solvent molecules and was found to arrest during the early stages of phase separation due to P3HT interchain crystallization. Cryogen-based scanning electron microscopy images of the gels further uncovered an interfibrillar network with characteristic pore sizes tens of nanometers in diameter. These interconnected polymer structures with hierarchical porosity were deposited as thin films via doctor blading, resulting in a 45% enhancement of light conversion efficiency compared to organic solar cells comprising active layers deposited from uncooled solutions. |
Wednesday, March 6, 2019 10:12AM - 10:24AM |
K49.00012: (Near-) Ambient Pressure XPS for Studying Surface Reconstruction of Hydrated Polymers Mikayla Barry, Emily C Davidson, Ethan J Crumlin, Rachel Segalman Polymer restructuring in response to environmental conditions has made surface characterization of polymers designed for use in hydrated applications difficult. Analysis techniques that provide nanoscale surface composition (e.g. X-ray Photoelectron Spectroscopy (XPS)) have been largely limited to use in vacuum, where the surface presentation no longer matches that of hydrated polymers. Consequently, characterization of the hydrated surface has been relegated to contact angle goniometry and vibrational spectroscopy techniques such as Raman and Sum Frequency Generation (SFG). We present the first synchrotron (Near-) Ambient Pressure XPS (AP-XPS) studies performed on polymer surfaces in contact with water vapor. Water adsorption on polydimethylsiloxane-based polymers was found to increase substantially for those containing even minimal amounts of amphiphilic side chains. The presence of hydrogen-bonding side chains also correlated with greater increases in water adsorption and decreases in silicon-character oxygen (associated with the polymer backbone) at 6 Torr relative to non-hydrogen-bonding side chains. |
Wednesday, March 6, 2019 10:24AM - 10:36AM |
K49.00013: Self-assembly of Functionalized Nanoparticles in Ordered Phases of Block Copolymers Supriya Gupta, Paresh Chokshi An emerging application of polymer nanocomposites is to generate self-assembly of nanoparticles leading to novel nanoscale materials with enhanced properties. As particle-based techniques, e.g. molecular simulation, are computationally intensive, we employ the self-consistent field theory (SCFT) combined with density functional theory (DFT) to examine the localization of nanoparticles in ordered domains of block copolymers. The nanoparticles are grafted with polymer chemically identical to either block of the copolymer. To ensure finite size of the particles and excluded volume interactions between species, the free energy is described using DFT. We study the localization of nanoparticles in lamellar and cylindrical morphologies. For lamellar phase, nanoparticles assemble either at the interface between two blocks or at the center of a block domain depending upon particle concentration and grafting density. In cylindrical phase, nanoparticles self-assemble at the center of the cylinders. The role of grafting density, particle size and composition on self-assembly behavior of particles in block copolymer is examined. The comprehensive understanding of factors affecting localization of nanoparticles enable us to control the particulate assembly for desirable material properties. |
Wednesday, March 6, 2019 10:36AM - 10:48AM |
K49.00014: Effect of Synthetic Parameters on Molecular Architecture and Adhesive Performance for Acrylic Emulsion Copolymers Sipei Zhang, Owen (Wen-Shiue) Young, Melinda Einsla, Josephine Eldredge, Vinita Yadav, Cynthia R. Leslie, Kebede Beshah, Alan Nakatani, Asghar Peera, William Griffith, Sarah R. Zolynski, Himal Ray, Cachae Pearson, Saswati Pujari, Sehban Ozair It is well known that both the composition and architecture of a polymer affect its performance as a pressure sensitive adhesive (PSA). However, the specific relationships of glass transition temperature (Tg), degree of branching, crosslinking density, and molecular weight with PSA properties are often complicated, and the variables can be difficult to isolate. Here we present a study examining the effects of acrylic monomer, feed time, and styrene content on the molecular architecture of emulsion-based copolymers with systematically varied composition, and their relationships with adhesive performance. The polymer architecture is elucidated using dynamic mechanical analysis (DMA), gel permeation chromatography (GPC), gel fraction/swell ratio (GF/SR), and 13C nuclear magnetic resonance (NMR) spectroscopy. It was found that the primary acrylic monomer had the most significant effect on polymer architecture, followed by styrene content, and then feed time. The resulting impact on adhesive and cohesive strength will also be discussed. |
Wednesday, March 6, 2019 10:48AM - 11:00AM |
K49.00015: Dramatic Mechanical Response of Polymer-metal Inclusions Based Metamaterials RITUPARNA GHOSH, Sourav Das, Abha Misra A periodic lattice of metal sphere (steel ball) is arranged in polydimethylsiloxane (PDMS) polymer matrix in multidimensional architecture. At multiple strains there is gradual increases in both the stress and energy absorption capability. Three-dimensional architecture demonstrated maximum loading capacity retaining its elastic behaviour. An enhancement of ~ 50% in absorption capability and stress at 40% strain is recorded as compared to one and two-dimensional architectures. The three-dimensional architecture also showed strain rate independent highly reversible behaviour for 1000 compression cycles at 30% strains and exhibit excellent mechanical stability. However, a dramatic drop in stress by ~ 100% was observed at higher strain (> 50%) in three-dimensional architecture as compared to other metamaterials. Point contacts between multiple disjoint steel balls, which form a periodic chain like structure play the key role in achieving enhanced strength and energy absorption and have importance in numerous mechanical applications where high strength and energy absorption are the prime requirement. |
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