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 V63: Electric Polarization in Polymer PhysicsFocus Live
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Sponsoring Units: DPOLY GSNP DCP DCOMP Chair: Rajeev Kumar, Oak Ridge National Lab; Yangyang Wang, Oak Ridge National Lab |
Thursday, March 18, 2021 3:00PM - 3:12PM Live |
V63.00001: Comparing Stockmayer Fluid Simulation and Experiment: Ion Solvation with Permanent Dipoles Cameron Shock, Issei Nakamura, Amalie Frischknecht, Mark J Stevens The solvation of ions in polymer membranes has been studied over many decades. Nevertheless, an understanding of the solvation mechanism involves various computational challenges. This is primarily because molecular simulations for ion solvation that can simultaneously consider both atomic and molecular length scales are still significantly limited, even in cases of non-polymeric solvents. In this study, we developed a coarse-grained Stockmayer fluid simulation to address this issue, treating solvent molecules as soft-core spheres with permanent dipole moments. In this talk, we validate our model concept by considering monovalent and divalent ions dissolved in various non-polymeric solvents, such as water and methanol. Despite model simplicity, the results of our simulations show striking agreement when compared with experimental data for the free energy and enthalpy of ion solvation. We will also discuss that the primary contribution to the solvation energy arises mainly from the first and possibly second solvation shells near the ions. |
Thursday, March 18, 2021 3:12PM - 3:24PM Live |
V63.00002: Polymer blends with enhanced dielectric properties enabled by rationally designed chain-packing behavior: a computational study Bing Zhang, Wenchang Lu, Xin Chen, Qiming Zhang, Jerry Bernholc Controlling nanostructure in polymers is important for many applications. For polymer dielectrics, rational nanostructure design may increase the energy storage capacity by enhancing either the dielectric constant or the dielectric breakdown strength. In our previous studies, we showed that by blending polymers with different periodicities, the dielectric constant can be enlarged due to free-volume expansion. In this work, we use molecular dynamics with classical force fields to simulate polymer blends with different morphologies, including extended and coiled chains. The results show that polyimide (PI) and polyetherimide (PEI) are miscible and tend to form extended blend structures instead of coiled blobs. Consequently, the polymer chains are packed closer and nano voids are dramatically reduced. The increased packing can significantly boost the dielectric breakdown strength and lead to greatly increased electric energy density in capacitor structures. The theoretical results are in very good agreement with experimental data [1]. |
Thursday, March 18, 2021 3:24PM - 4:00PM Live |
V63.00003: How to Define Electric Potential in a Polarized Polymer Electrolyte Why is it Important? Invited Speaker: Nitash Balsara Polymer electrolytes comprise mobile ionic species, usually both cations and anions, but are electronic |
Thursday, March 18, 2021 4:00PM - 4:12PM Live |
V63.00004: Dynamics of a Single Polyampholyte Chain Kevin Silmore, Rajeev Kumar Polymers that feature both positive and negative charges, also known as polyampholytes, represent a class of materials that hold promise for a new generation of energy storage devices (e.g., higher performance capacitors), the design of which will require knowledge of the underlying structure and dynamics. The dynamics of neutral polymers was studied decades ago by pioneers such as Rouse, Zimm, and de Gennes, but the dynamics of polyampholyte systems has been paid less attention, due in part to the complexity of chemical synthesis. Here, we develop a theory for the dynamic structure factor for a single polyampholyte chain under external electric fields and under weak internal fluctuations. We find deviations in scaling from the classic Rouse theory based on the distribution of charges and make predictions for scattering experiments performed on such compounds. |
Thursday, March 18, 2021 4:12PM - 4:24PM Live |
V63.00005: Density functional theory for charge regulation of inhomogeneous weak polyelectrolytes Alejandro Gallegos, Jianzhong Wu In contrast to strong polyelectrolytes, weak polyelectrolytes present electrostatic charges in accordance with the solution pH and the local chemical environment. The pH-responsive behavior is advantageous for use in smart systems to achieve specific functions such as targeted drug delivery and controlled release. Unfortunately, a quantitative description of such charge regulation behavior remains challenging. While there has been significant progress to describe weak polyelectrolytes in the bulk and near an interface, these studies typically neglect electrostatic correlations along the polymer backbone. Furthermore, existing methods cannot capture local electrostatic correlations for inhomogeneous weak polyelectrolytes. In this talk, we present a new theoretical framework for weak polyelectrolytes by coupling a molecular thermodynamic model for chemical reactions with the polymer DFT. By incorporating correlation effects into the conventional titration models, we can describe the behavior of weak polyelectrolytes in agreement with experimental data. This theoretical model is used to study the surface forces mediated by weak polyelectrolytes and generate insight into the design of bioadhesives. |
Thursday, March 18, 2021 4:24PM - 4:36PM Live |
V63.00006: Charge transport of nano-confined ionic liquids in ion gels Alireza Bandegi, Kyungtae kim, Reza Foudazi Ionic liquids (ILs) have attracted significant interest due to their unique properties including high thermal stability, negligible vapor pressure, and high ionic conductivity and specific capacitance. To enhance the practicality of employing ILs in different applications, it is important to blend them with structuring polymers to form physically or chemically crosslinked networks, known as ion gels. Using block copolymers as polymer matrix provides the opportunities to control the gel nanostructure (lamellar, hexagonal, cubic, and gyroid) and physical properties through variation of the copolymer block lengths, architecture, or chemistry. In this study, nanostructured ion gels are prepared through polymerization of lyotropic liquid crystals (LLCs) made of monomers (styrene and divinylbenzene), ionic liquid ([EMIM][BF4]), and amphiphilic block copolymers. We investigate the molecular dynamics of nano-confined ionic liquids in these ion gels by broadband dielectric spectroscopy. |
Thursday, March 18, 2021 4:36PM - 4:48PM Live |
V63.00007: Highly mobile oriented amorphous fraction in semicrystalline ferroelectric polymers and its unique contribution to electrostrictive and piezoelectric properties Lei Zhu, Yanfei Huang, Guanchun Rui Piezoelectric polymers hold great potential for various electromechanical applications, but only show low performance, with |d33| < 30 pC/N. We prepared a highly piezoelectric polymer (d33 = -62 pC/N) based on a biaxially oriented poly(vinylidene fluoride) (BOPVDF, crystallinity = 0.52). After unidirectional poling, macroscopically aligned samples with pure β crystals were achieved, which showed an unprecedentedly high spontaneous polarization (Ps) of 140 mC/m2. Given the theoretical limit of Ps = 188 mC/m2 for the neat b crystal, the high Ps could not be explained by a simple two-phase model (i.e., the crystalline and the amorphous phases). Instead, we deduce that a significant amount (at least 0.25) of an oriented amorphous fraction (OAF) must be present between these two phases. Experimental data suggest that the mobile OAF resulted in the negative and high d33 for the poled BOPVDF. The plausibility of this conclusion was supported by molecular dynamics simulations. |
Thursday, March 18, 2021 4:48PM - 5:00PM Live |
V63.00008: Dynamics of Solid Polymer Electrolytes with High Dielectric Constants Danielle DeJonge, Shiwang Cheng, Robert Ferrier Solid polymer electrolytes (SPE) are next-generation electrolytes for rechargeable batteries, fuel cells, and desalination membranes. However, current SPEs suffer from low ionic conductivity due to a lack of understanding of the ion transfer in polymers. Through combining broadband dielectric spectroscopy (BDS) and rheology, the ion dynamics of lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt-doped polyelectrolytes have been investigated, including poly(epichlorohydrin) (PECH), poly(propylene oxide) (PPO), and poly(butylene oxide) (PBO). While increasing dielectric constant of the polymer matrix increases the solvation of the ions, the ultimate ion dynamics have been strongly regulated by the dynamics of the matrix. The talk will also present the relationship between increasing polarity on conductivity, the relaxation time of the polymer, and ion transport of these SPEs of high dielectric constant. |
Thursday, March 18, 2021 5:00PM - 5:12PM Live |
V63.00009: Direct mapping of local polar distortion in relaxor ferroelectric polymers by using atomic force microscope infrared-spectroscopy YANG LIU, Bing Zhang, Wenhan Xu, Aziguli Haibibu, Zhubing Han, Wenchang Lu, Jerry Bernholc, Qing Wang Relaxor ferroelectrics are a well-known disordered system whereas the local polar structure at nanoscale is essential to understanding of their striking properties. Here we use atomic force microscope infrared-spectroscopy (AFM-IR) to provide direct mapping of local conformational configuration in relaxor ferroelectric polymers [Y. Liu et al, Nature Mater. 2020, 19, 1169]. We found that chemical pattern of all-trans conformation-representing the ferroelectric β phase-is strongly spatially dependent in relaxor polymers in contrast to normal ferroelectric composition with a nearly homogenous chemical pattern. Moreover, our local spectra clearly reveal the strong position-dependence of local chain conformation in relaxor ferroelectric polymers. We show that this feature of relaxors revealed by AFM-IR technique is independent of measurement mode demonstrating that chain conformational disorder is inherent to relaxor ferroelectric polymers. |
Thursday, March 18, 2021 5:12PM - 5:24PM Live |
V63.00010: Operando structure determination of mixed conducting polymers Bryan Paulsen, Ruiheng Wu, Christopher J. Takacs, Joseph Walter Strzalka, Qingteng Zhang, Alexander Giovannitti, Michael Toney, Jonathan Rivnay Polar conjugated polymer based organic mixed ionic-electronic conductors (OMIECs) are exciting class of materials for electrochromic, charge storage, biological sensor, neuromorphic, and electrochemical transistor applications, amongst others. In these electrolyte swollen applications the structure of OMIECs are not constant, rendering static ex situ characterization inadequate. Here, we report the grazing incidence x-ray scattering of the prototypical polythiophene/polyelectrolyte blend, PEDOT:PSS, and the glycolated polythiophene, p(g2T-TT), under operating conditions (i.e. exposed to electrolyte, at controlled electrochemical potential). This has required the development of new in situ/operando cells that overcome electrolyte absorption/scattering to preserve the scattered x-ray intensity from the OMIEC film. Steady-state and time-resolved measurements reveal the profound effect of electrolyte on crystallite lattice spacings and quantify the structural kinetics that accompany electronic charging and discharging, respectively. Coupled with optical and X-ray spectroscopy, we correlate these results with doping composition, charge carrier dynamics, and charge trapping, which gives insight into electronic transport in these materials. |
Thursday, March 18, 2021 5:24PM - 5:36PM Live |
V63.00011: Copper Nanowire Infused Facemasks Cameron Jorgensen, Dustin Gilbert, Daniel Bryan, Thomas Gardner Denes, Anne Murray The COVID 19 pandemic has created high demand for face masks. The goal is to develop a method for reusing or recycling old masks into new masks for continued use without pathogens they collect. Most masks are made of a type of polypropylene that can be melted to a temperature that would kill bacteria. Ideally, hospitals could take the melted plastic and make their own masks. One method includes electrospinning, which is placing a high voltage on a metal plate and as the plastic polarizes it will attract to the metal plate as a thin string, creating a woven mesh for use as a mask again. |
Thursday, March 18, 2021 5:36PM - 5:48PM Live |
V63.00012: Ion partition in polyelectrolyte nanogels Alexandros Chremos, Matan Mussel, Peter Basser, Jack Douglas, Ferenc Horkay The partition of monovalent and divalent ions in polyelectrolyte gels plays a critical role in biological function, however, no generally accepted model currently exists that can provide a microscopic description of ion partition in polyelectrolyte gels. The challenge in modeling of such systems is due to the coupling between the polyelectrolyte chain configurations and the spatial distribution of the ionic species in solution. We perform molecular dynamics simulations of a minimal model of a polyelectrolyte nanogel particle in solution with an explicit solvent and ions, where the relative strength of dispersion interactions between the solvent and the charged species defines the solvent quality and the position of the ion along the Hofmeister series. Our findings demonstrate that the architecture of the polyelectrolyte gel and the solvent play a crucial role in gel swelling to the addition of salt and the ion partitioning between the gel and the surrounding solution. Overall, our findings provide a guideline for the development of a more predictive theory of the thermodynamic and transport properties of these complex systems. |
Thursday, March 18, 2021 5:48PM - 6:00PM On Demand |
V63.00013: The impact of chemical modification on charge injection at metal/polyolefin interfaces Yiyuan Wang, Mikael Unge, Sari Laihonen, Arash A Mostofi The process of charge injection at metal/polymer interfaces is crucial to many areas of research and technology, such as organic light emitting and harvesting devices, high-voltage capacitors and cables. In this work, we study charge injection at metal/polymer interfaces for two polymers commonly used in high-voltage applications, namely polyethylene (PE) and polypropylene (PP). Using first-principles electronic structure methods, we compute charge injection barriers at model aluminium/PE and aluminium/PP interfaces. We show that the introduction of polar chemical groups (e.g., -COOH, -CH2Cl, and -CHO) in the polymer chains at the interface can tune the intrinsic charge injection barrier significantly. We take into account of thermal disorder by averaging over a large ensemble of interface structures obtained from first-principles molecular dynamics trajectories. Our results suggest the possibility of rational design of metal/polymer interfaces via localised chemical modification. |
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