Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session D34: Charged and Ion-Containing PolymersFocus
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Sponsoring Units: DPOLY Chair: Christopher Evans, University of Illinois at Urbana-Champaign Room: 506 |
Monday, March 2, 2020 2:30PM - 2:42PM |
D34.00001: Role of chain architecture and composition on dynamics and ionic solvation in polyether-based electrolytes Peter Bennington, Daniel Sharon, Michael Webb, Chuting Deng, Juan De Pablo, Paul F Nealey, Shrayesh Patel In recent years a great number of new polymer electrolytes have been developed towards improved performance and stability of energy storage devices. These new materials typically include polyether moieties to facilitate efficient ion transport. However, the presence of additional non-conducting groups influences the ability of polyethers to solvate ions and hopping between these solvation sites. We have examined a number of polyether-based electrolytes in linear, block, graft, and blend configurations to explore how chemical and physical interactions between different components affects ionic conductivity. Using a combination of impedance spectroscopy, vibrational spectroscopy, and atomistic simulations, we gain insight into the degree of ion conductivity, ionic interactions, and polymer dynamics of these materials. Both the polymer-polymer interaction strength and segmental mobility of non-solvating components show an effect on the overall conductivity and connectivity of ion solvation sites. These findings highlight the need for more complete models to account for various length scales of interaction in these nonuniform material systems. |
Monday, March 2, 2020 2:42PM - 2:54PM |
D34.00002: Self Diffusion Dynamics and Viscoelasticity of Fluoresently Labeled Polymerized Ionic Liquids Qiujie Zhao, Christopher Evans Scaling relationships for viscosity and diffusion coefficient as a function of degree of polymerization (N) are well-characterized in neutral polymers. We have synthesized fluorescently-labeled polymerized ionic liquids (f-PILs) with a broad range of molecular weights to understand these relationships in dry, ionic polymers with a charge on every repeat unit. Fluorescence recovery after photobleaching (FRAP) is used to measure polymer self-diffusion coefficients (D ) using the post-bleached fluorescence images and fitting the intensity to a Gaussian profile over time. The zero-shear viscosity was measured via rheology. In the shortest f-PILs, the ionic interactions between imidazolium and bis(trifluoromethane sulfonamide) have little effect on extending the terminal regime. However, the terminal region did extend to lower frequencies as N increased. Interestingly, the wide-angle x-ray scattering shows an amorphous halo and anion-anion peak, but no longer range ionic aggregate peak which we assign as the origin of the rheological behavior. Scaling relationships with molecular weight will be discussed. |
Monday, March 2, 2020 2:54PM - 3:06PM |
D34.00003: First consideration of density scaling of the dynamic and thermodynamic properties in polymerized ionic liquid. Malgorzata Musial, Zaneta Wojnarowska, Shinian Cheng, Adam Holt, Charles M. Roland, Eric Drockenmuller, Marian Paluch The density scaling idea is a general feature of glass-forming materials, e.g., van der Waals liquids and polymer melts. According to this concept, the data of dynamic properties collected in isobars and isotherms collapse to a single curve when expressed versus TVγ, where T is temperature, V is specific volume, and γ is scaling exponent being a material constant independent of thermodynamic conditions. |
Monday, March 2, 2020 3:06PM - 3:18PM |
D34.00004: WITHDRAWN ABSTRACT
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Monday, March 2, 2020 3:18PM - 3:30PM |
D34.00005: Charging Neutral Polymer by Simple and Macro Ions in Solution Manuela Ferreira, Benxin Jing, Yingxi Elaine Zhu It is recently reported that neutral polymers, such as poly(ethylene oxide) (PEO), could behave like weakly charged polyelectrolyte in highly polar solvents. We have examined the ion charging and resulting conformational structure of single PEO chains of varied molecular weight in water and mixed solvents by fluorescence correlation spectroscopy (FCS)-photon counting histogram (PCH) experiments. PCH results indicate that PEO becomes positively charged in LiCl-added solution, yet the measured electrical potential of PEO in LiCl solution decreases rapidly with the addition of multivalent polyoxometalate (POM) polyanion. The net charge of single PEO chains in solution shows strong dependence on the concentration ratio among Li+, POM, and monomer. FCS results show non-monotonic change of measured hydrodynamic size of single PEO chains in LiCl or LiCl-POM added solution with increasing ionic concentration, suggesting distinct ionic binding and screening effects. Further, the addition of a solvent with weak hydrogen-bond donor capabilities could further weaken the binding POM with PEO, but not so for the binding of Li+ cation with PEO. Therefore,the formation of PEO-Li+-POM complexes in different solvent mixture could lead to a facile process of PEO-based ionomers of tunable net charge |
Monday, March 2, 2020 3:30PM - 3:42PM |
D34.00006: Addition of Zwitterions to Single-ion Conducting Ionomers Wenwen Mei, August Rothenberger, Josh Bostwick, Robert Hickey, Ralph H Colby Applications of polymeric materials in energy-related areas are severely hampered by their limited conductivity at room temperature. The continuing pursuit of maximizing their room-temperature conductivity has driven novel design of polymeric systems. Ion aggregates are believed to be one of the major causes that stymies the ion conduction, due to the decreased mobile ion density and slowed segmental motion. Recently, much attention was drawn on additives that increase the dielectric constant due to its significant role in promoting conduction of small mobile ions such as lithium. Zwitterions are promising candidates for this purpose, owning to a large molecular dipole from covalently bonded cation and anion. Here, we studied a series of imidazolium-sulfonate zwitterions that are used as additives in single-ion conducting ionomers. Significant increases in both dielectric constant and ionic conductivity are reported. This work highlights the significance of zwitterion for promoting the conductivity, which benefits their further applications in a wide range of polymers. |
Monday, March 2, 2020 3:42PM - 4:18PM |
D34.00007: Polymer Electrolytes Containing Solvate Ionic Liquid and Beyond Invited Speaker: Masayoshi Watanabe Certain molten solvates of Li salts can be regarded as solvate ionic liquids (SILs). A typical example is equimolar mixtures of glymes and Li[TFSA]([TFSA]=[NTf2]). The amount (activity) of free glyme is a trace in [Li(glyme)][TFSA], and thereby can be regarded as solvate ionic liquids. Unlike conventional electrolytes, the solvation of Li+ by the glyme forms stable and discrete solvate ions ([Li(glyme)]+) in the SILs. Polymer electrolytes composed of ABA-triblock copolymers and [Li(glyme)][TFSA] SILs are proposed to simultaneously achieve high ionic conductivity, thermal stability, and a wide potential window. Intriguing points of the polymer electrolytes are decoupled ion transport from segmental motion of the matrix polymer and the persistence of solvate structure in the polymeric phase. Recently, we find that Li+ hopping conduction, which cannot be explained by conventional Stokes law, emerges in certain highly concentrated molten solvate electrolytes. Li+ diffuses faster than the solvent and anion, and thus the evolution of Li+ hopping conduction is confirmed, which leads to a higher Li+ transference number. Possible application of these new electrolytes will be discussed. |
Monday, March 2, 2020 4:18PM - 4:30PM |
D34.00008: The Overlap Concentration in Strong Polyelectrolytes Mark Stevens, Jon Bollinger, Gary Grest, Michael Rubinstein Understanding strong polyelectrolytes in solution is a major challenge for theory. We have simulated a strong polyelectrolyte in a salt free solution for monomer numbers N =10 to 1600. We calculated the overlap concentration c* and find that c*scales as N -2.5. Morover, not until very large N ≥ 800 does the end-to-end distance at c* approach the infinite dilution limit. The chains at large N are fully stretched at c*, while at small N substantial stretching occurs below c*. For large N the chains are also rodlike in that the form factor at c* is almost that of a straight line for lengths corresponding from a few bond lengths to the end-to-end distance. |
Monday, March 2, 2020 4:30PM - 4:42PM |
D34.00009: Salt Effect on Swelling of Polyelectrolyte Networks with Brush-like Strands Michael Jacobs, Zilu Wang, Andrey Dobrynin We study effect of added salt, density of ionized groups and molecular |
Monday, March 2, 2020 4:42PM - 4:54PM |
D34.00010: Electrostatic Effects on Charged Block Copolymer Melts Yihao Liang, Boran Ma, Monica Olvera De La Cruz Electrostatic interactions can enrich the phase behaviors of charged block copolymer melts. However, due to limitations of simulation techniques and theoretic tools, the phase behavior of charged block copolymers remains elusive. In this talk we implement the event-chain Monte Carlo (ECMC) algorithm to describe charged block copolymer melts. ECMC is a new simulation technique which satisfies the maximum global balance and is good for systems with long relaxation time. Equipped with cell-veto method, ECMC can achieve O(N) time complexity for each cycle. Our work shows that ECMC is a promising approach to describe charged copolymer systems. |
Monday, March 2, 2020 4:54PM - 5:06PM |
D34.00011: Transference Numbers of Aqueous Polyelectrolyte Solutions Tyler Lytle, Arun Yethiraj The demand for lithium-ion batteries with improved energy density and charging rates is growing, because of increasing use of consumer electronics and electrification of vehicles. However, lithium-ion batteries have several issues including long charging times. A potential route to circumvent this issue and increase the battery energy density is high transference number electrolytes. Lithium transference numbers using traditional liquid electrolytes are less than 0.5, which indicates the anion carries most of the current. In order to increase this transference number, it has been suggested to use polyelectrolyte solutions in which the polyanion mobility is less than the lithium ion mobility, but molecular-level understanding of counterion dynamics in polyelectrolyte solutions is underdeveloped. Our work uses molecular dynamics simulations of coarse-grained polymer models to elucidate how chain length, counterion size, and solution concentration affect the ion transference number in solution. These simulations show ion transference numbers depend non-monotonically on chain length, and smaller counterions have lower transference numbers. These simulation results can be used to guide experimental design of electrolytes with high lithium ion transference numbers. |
Monday, March 2, 2020 5:06PM - 5:18PM |
D34.00012: Hydration Phenomena in Sulfonated Poly(arylene ether sulfone) Membranes Chengyuan Wen, Britannia Vondrasek, Judy Riffle, Jack Lesko, Shengfeng Cheng The hydration mechanism of ionic polysulfones remains poorly understood, which hinders their utility in water purification membranes. Differential scanning calorimetry (DSC), density measurements, and molecular dynamics simulations are combined to improve molecular-scale understanding of how water interacts with different parts of sulfonated polysulfones as water uptake is varied. The results reveal a threshold value of water uptake below which virtually all water molecules are located in the primary hydration shell of ions (Na+ and SO3-) and polar groups (SO2 and ether linkages). At higher water uptake, a significant fraction of the absorbed water molecules become more loosely associated with the polymer. This transition is indicated by the gradual appearance of a melting endotherm in DSC analysis, a maximum in measured density of the hydrated polymer, and appearance of water molecules with a bulk-like state in simulations. The simulation results further indicate that interactions between ions (Na+ and SO3-) and polar groups, particularly SO2, play an important role in the hydration behavior of sulfonated polysulfones. |
Monday, March 2, 2020 5:18PM - 5:30PM |
D34.00013: Dynamics at Internal Interfaces in Ionizable Polymer Blends Jayme Alger, Manjula Senanayake, Gary Grest, Dvora Perahia Ionizable polymers have found a large number of applications in the water-energy nexus, enabled by the segregation of the polymers into ionic and non-ionic domains. The morphology of the ionic domains varies as a function of numerous factors, among them are the number of ionic groups, their distribution and the topology of the polymers. To understand the segregation process, we probe the evolution and dynamics of internal interfaces formed by blends of polystyrene (PS) and polystyrene sulfonate (PSS) below their entanglement length using atomistic molecular dynamic simulations for temperatures above the glass transition temperature of either polymer. Melts of PS and PSS blends with varying sulfonation fractions with Na+ and N(CH3)4+ counterions were followed as a function of time. The development of the internal interface of the charged and the non-charged polymers will be discussed. We will compare blends of PS and PSS which can globally phase separate with diblock copolymers of PS and PSS which phase separate only locally. |
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