Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session A03: Confinement, Dynamics, and Ion Interactions in Ion-Containing Polymers IFocus Live
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Sponsoring Units: DPOLY DSOFT Chair: Moon Park, Pohang Univ of Sci & Tech |
Monday, March 15, 2021 8:00AM - 8:12AM Live |
A03.00001: Theory of transport of ions and macroions in heterogeneous polymer materials Murugappan Muthukumar We have developed a general theory to describe transport of ionic species in disordered polymer materials by considering electrostatic binding/unbinding of mobile ions with the matrix. The contributions to ionic conductivity from ion hopping among spatially correlated domains and direct sliding along the skeletons of the matrix are taken into account in deriving closed-form formulas. The theory is valid for the mobility of both electrolyte ions and charged macromolecules. When the charged macromolecule is topologically frustrated, extreme violations of Einstein’s law of mobility emerge during practical time scales of experimentation. Comparison between the predictions of the theory and experimental results on ionic conductivity will be presented. |
Monday, March 15, 2021 8:12AM - 8:24AM Live |
A03.00002: Structure and Dynamics of Hydrated Precise Sulfophenylated Polyethylene Polymers from Simulation Bryce Thurston, Benjamin Paren, Karen Winey, Mark J Stevens, Amalie Frischknecht Design of novel materials for proton exchange membranes can be aided by a greater understanding of the molecular mechanisms of ion transport. We study a precisely-spaced sulfophenylated polyethylene polymer (p5PhSA) in which sulfonate anions are covalently bound to the pendant phenyl groups and are neutralized by hydronium ions. We perform molecular dynamics simulations at different water contents. Sulfonate groups and water molecules form percolating nanochannels that phase separate from the polymer backbone, allowing for transport of hydronium ions through the system. The inomer peak in computed structure factors exhibits a shift in position to lower wave vector and quenching in magnitude relative to the amorphous halo with increasing water content, similar to x-ray scattering data. We use computed partial structure factors to better understand these changes. Higher water content also results in hydronium ions being increasingly coordinated by water and decreasingly coordinated by sulfonate groups. Finally, rotation rates and diffusion constants of water molecules are found to exhibit exponential decay as a function of sulfonate to water molar ratio. |
Monday, March 15, 2021 8:24AM - 8:36AM Live |
A03.00003: Heterogeneity in composition and dynamics in supercooled branched ionomers Trung Nguyen, Han Noe Umana Kossio, Monica Olvera De La Cruz Ionomers are useful in a wide range of applications including shape-memory materials, anti-microbial surfaces, and membranes for fuel cells. Cycled thermal treatment of a family of poly (3-sulfopropylmethacrylate-ran-methyl methacrylate) ionomers with different charge fractions shows a broadening glass transition range, which suggests compositional heterogeneity present in these systems. Using coarse-grained models and simulations, we characterize the thermal behaviors of these ionomers, and correlate them with the non-uniformity of the spatial distribution of monomer composition. We also examine the correlation between polymer dynamics during liquid-supercooled and supercooled-glass transitions and the ionomer charge fraction and side chain length. The findings offer insight into the convoluting interplay between key factors such as long-range Coulombic interactions in condensed phases, and the conformational entropy of the branched polymers and of the side chains. |
Monday, March 15, 2021 8:36AM - 8:48AM Live |
A03.00004: Weakening of solvation-induced ordering by composition fluctuation Xian Kong, Kevin J Hou, Jian Qin Selective ion solvation has been identified as a driving force for enhanced ordering in salt-doped block polymers. Recent comparison between mean-field theory and experimental results suggests that the degree of enhancement is limited, necessitating the use of a solvation radius that is larger than physical ion size. Following the standard Brazovskii treatment, we show that this weakened solvation may be partially caused by the composition fluctuation near the ordering transition. The competition between solvation-induced ordering and destabilizing fluctuation effects is revealed by phase diagrams generated at different salt doping conditions. Further, the salt-doping is found to affect the location of the scattering peak non-monotonically, also due to the competition between solvation and fluctuation. |
Monday, March 15, 2021 8:48AM - 9:00AM Live |
A03.00005: Rotational Motion of Water Molecules Within the Polyelectrolyte Brush Layer Serving as a Soft and Active Nanoconfinement Siddhartha Das, Harnoor Sachar, Turash Pial, Bhargav Chava It is well known that the rotational dynamics of water is strongly altered in confinement. Polyelectrolyte (PE) brushes, formed by grafting charge-bearing PE molecules in close proximity, serve as an important class of stimuli-responsive nanomaterial. Molecular Dynamics (MD) simulations have revealed that PE brushes act as a form of lateral nanoconfinement and significantly reduce the translational mobility of the trapped water molecules. We perform an all-atom MD study to probe the rotational dynamics of water molecules inside densely grafted PE brushes. PE brushes represent a special case of soft and active nanoconfinement, where the source of confinement itself forms hydrogen bonds with the water molecules and affects their rotational dynamics. We observe that the rotational diffusivity of water reduces monotonically in all 3 principal directions with increasing grafting density of the brushes (or increasing ionic concentration within the PE layer). This trend is at odds with conventional “water-in-salt” solutions (highly concentrated aqueous electrolytes) and results from the unique topological constraints imposed by the densely grafted PE chains. |
Monday, March 15, 2021 9:00AM - 9:12AM Live |
A03.00006: Comparison of Ion Transport in Single-ion and Salt-doped Block Copolymers: A Coarse-grained Molecular Dynamics Study Mengdi Fan, Kuan-Hsuan Shen, Lisa M. Hall Nanostructured block copolymers (BCPs) are of interest as solid-state electrolytes because they can allow for both ion conduction and mechanical robustness at the same time. Single-ion BCPs, with anions tethered to the conducting block of polymer backbone, have the potential to enhance the transference number and improve performance. We leverage coarse-grained molecular dynamics (MD) simulations to compare ion transport in salt-doped versus single-ion BCPs. Specifically, we calculate conductivity and transference number from simulations with an applied electric field, and focus on the effects of ion concentration and polymer dielectric constant. At low ion concentration, salt-doped systems have faster ion diffusion yet lower cation conductivity compared to analogous single-ion BCPs, while the cation conductivities are similar at high concentration. The cation conductivity difference between two types of BCPs decreases at higher dielectric constant. Thus, in the series of materials studied here, the potential advantage of single-ion systems is only relevant in situations where ionic aggregation is a concern. |
Monday, March 15, 2021 9:12AM - 9:24AM Live |
A03.00007: Structural and transport characteristics of battery electrolytes based on lithium poly(bis-nonenyl malonato borate) in carbonate solvents Ajay Muralidharan, Tyler Lytle, Arun Yethiraj Lithium poly(bis-nonenyl malonato borate) in propylene carbonate (Li poly-BNMB/ PC) has been suggested as a battery electrolyte because of extraordinarily high lithium transference number at a relatively low degree of polymerization. This is in contrast to a recent coarse-grained simulation study which argued that the transference numbers in polyelectrolyte solutions were lower than the corresponding monomeric electrolyte. In this work, we report a simulation study based on a fully atomistic non-polarizable force field for Li poly-BNMB in carbonate solvents. We simulate a variety of polymerization indices and alkyl spacer lengths at experimentally relevant concentrations. We elucidate the influence of polyion chain behavior and ion correlations on the structural and transport characteristics of the system. |
Monday, March 15, 2021 9:24AM - 9:36AM Live |
A03.00008: Transport mechanisms underlying ionic conductivity in nanoparticle-based single-ion electrolytes Sanket Kadulkar, Delia Milliron, Thomas M Truskett, Venkatraghavan Ganesan Improving the ionic conductivity of electrolytes, while maintaining high lithium transference numbers is crucial for reliable and high-performing lithium-ion battery technologies. Nanoparticle-based electrolytes, in which nanoparticles are embedded in ion-conducting solid polymers or liquids, have emerged as a promising platform in this regard. In this work, we introduce a coarse-grained multiscale simulation approach to identify the mechanisms underlying the ion mobilities in nanoparticle-based single-ion conductors and to clarify the influence of key design parameters on conductivity. Our results suggest that for the experimentally studied electrolyte systems, the dominant pathway for cation transport is along the surface of nanoparticles, in the vicinity of nanoparticle-tethered anions. Within this picture, we identify the influence of nanoparticle volume fraction, anion and cation choices, and solvent (host) polarity on the ionic conductivity. Together, our results provide a complete picture for design considerations in single-ion conducting electrolytes based on nanoparticle salts. |
Monday, March 15, 2021 9:36AM - 9:48AM Live |
A03.00009: Entropic localization of plasmids in nanofluidic compartments Zezhou Liu, Xavier Capaldi, Lili Zeng, Rodrigo Reyes Lamothe, Walter Reisner Bacteria must stably partition their plasmids to their daughter cells upon division. While purely random partitioning can theoretically ensure the stable transmission of plasmids to daughter cells, it is not clear that plasmid partitioning is random. Studies tracking plasmids in vivo show that multi-plasmid clusters present at the cell poles, but the roles played by the cell geometry and chromosome-plasmid interactions are still unclear. Here, we present a nanofluidic device with compartments simulating the confinement induced by a cell membrane. The compartments can be opened and closed by pneumatically actuating the thin membrane lid. The cavities are elliptical with a width varying from around 200 nm to 2 um. A differentially stained T4 DNA molecule and one plasmid molecule are introduced inside the compartment and monitored in real-time from their fluorescence signals. We find that the plasmid prefers the peripheral of the cavity as has been observed in in vivo measurements in E. Coli, forming a ring shape distribution. In addition, as the cavity aspect ratio increases, the plasmid shows a preference for the cavity poles. Our results suggest that the free energy landscape formed by chain-chain interaction and the confinement geometry helps promote plasmid localization. |
Monday, March 15, 2021 9:48AM - 10:00AM Live |
A03.00010: The relation between ion transport and relaxation dynamics in polymers Matthew Reynolds, Daniel L. Baker, Pieter Magusin, Peter Olmsted, Johan Mattsson Li-ion batteries are important as power sources for portable devices (e.g. laptops and mobile phones) and their use is predicted to grow substantially in the near future. Unfortunately, we lack safe, easy-to-process (low-cost), ideally mechanically flexible batteries. A possibility is solvent-free polymeric electrolytes. However, a key challenge is to decouple ionic transport from segmental relaxation and thus achieve good transport properties and mechanical rigidity. Previous work has varied the degree of decoupling in polymers by altering their properties (such as fragility, glass-transition temperature, chain flexibility). However, there is no clear understanding of the mechanisms behind this decoupling phenomenon. We here present work to help understand the decoupling between ionic transport and polymer dynamics. We will discuss experimental work on homo- and co-polymers where we have studied structure, relaxation dynamics and ion transport using dielectric spectroscopy, DSC, rheology, x-ray scattering, NMR and AFM. Results will be presented in the context of different models and ideas suggested in the literature to address the observed decoupling. |
Monday, March 15, 2021 10:00AM - 10:36AM Live |
A03.00011: Mechanisms of Ion Transport in Polymeric Ionic Liquids Invited Speaker: Venkatraghavan Ganesan Polymeric ionic liquids (PILs) are an emerging class of materials which combines the attractive properties of ionic liquids with the sequence complexity and mechanical characteristics of macromolecules. While significant advances have occurred in the context of synthesis and characterization of such materials, comparatively less understanding exists on the mechanisms underlying ion transport in such materials. In this talk, I discuss some recent developments in the context of PILs trelating to the issue of ion transport in such materials.We focus on the mechanisms of ion transport in such materials, the influence of counterions, and whether such materials do live upto the promise of hgh transference numbers. |
Monday, March 15, 2021 10:36AM - 10:48AM On Demand |
A03.00012: Effect of Interfacial Polymer Layer on Ion Transport in Hybrid Ceramic-Polymer Solid Electrolytes Manuela Ferreira, Yingxi Elaine Zhu, Robert Schmidt, Fan Xu, Mei Cai Hybrid ceramic-polymer membranes have emerging as new solid-state electrolytes (SSE) to promise high ion conductivity, strong mechanical strength, and easy processing, however the inherent incompatibility between inorganic ceramic and organic polymer remains a great challenge for their applications. In this work, we investigated the interaction of polyethylene oxide (PEO) based copolymer interfacial layer with both inorganic garnet-type LLZO ceramic and PEO electrolytes. With the interfacial copolymer layer, we observed much improved interfacial contact between LLZO and PEO membranes with considerably lowered bulk resistivity. We further examined the effect of copolymer content and interfacial layer thickness on the ion conductivity and electrochemical window of inorganic-organic composite SSEs. |
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