Graduate Student Seminar
November 22, 2024
12:45 p.m. ET
Wean Hall 7500
Self-Assembled Water Channels in Fluorine-Free Copolymers for Fast Proton Conductivity
While perfluorosulfonic acid polymers are widely used as proton-exchange membranes (PEMs), concerns arising from fluorine have stimulated interest in hydrocarbon-based PEMs. In previous work, we studied a linear polyethylene with a phenylsulfonic acid pendant group precisely on every fifth carbon and found the proton conductivity to exceed 0.1 S/cm above 65% relative humidity at 40 °C. Here we explore copolymers and terpolymers with lower ion exchange capacities to improve the processability and mechanical properties. By combining novel ROMP synthesis, X-ray scattering, FTIR spectroscopy, pulse-field gradient NMR, electrochemical impedance spectroscopy, and all-atom molecular dynamics simulations, we are establishing design rules to produce nanoscale water channels with high proton conductivity. From the simulations we extract quantitative information about the self-assembled water channels in the hydrated polymers via cluster analysis, channel width distributions, and fractal dimensions. From the spectroscopy methods, we probe the local structure and relaxations of water in the hydrated membranes. Notably, a moderate reduction in sulfonation level improves the mechanical toughness while maintaining high proton conductivity in these new fluorine-free PEMs.
Karen I. Winey, Harold Pender Professor of Engineering, University of Pennsylvania
Winey is the Harold Pender Professor of Engineering and Applied Science at the University of Pennsylvania with a 50:50 appointment between Chemical and Biomolecular Engineering and Materials Science and Engineering. Karen’s current research interests focus on (1) ion and proton conduction in polymer for a variety of electrochemical applications including batteries, fuel cells, and electrolyzers, (2) polymer-to-polymer chemical upcycling of polyolefins to functionalized polyolefins, and (3) nanoparticle dynamics in polymer melts and polymer electrolyte brushes. Her approach typically includes model materials, careful processing, and thorough characterization of morphology and properties, and often directly couples to theory and simulations. Karen has also held a variety of service and leadership positions and is currently serving on the APS Council and the Scientific Advisory Board for the Max Planck Institute of Polymer Research. In addition to earlier recognitions, Karen was recently awarded the 2020 Braskem Award by AIChE, fellowship in the American Association for the Advancement of Science in 2022, and the 2023 ACS Award in Polymer Chemistry.