Regensburg 2022 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 46: Poster Session: Complex Fluids, Soft Matter, Active Matter, Glasses and Granular Materials

DY 46.9: Poster

Donnerstag, 8. September 2022, 15:00–18:00, P2

Diffusion in a sulfonated co-polynaphthoyleneimide proton exchange membrane studied by NMR — •Celine Wolter, Alexei Privalov, and Michael Vogel — TU Darmstadt, Institut für Physik kondensierter Materie, Darmstadt, Germany

Nowadays, most fuel cells are based on proton-exchange membranes such as Nafion, which contain fluorine and therefore have some disadvantages for disposal. One alternative are flourine-free hydrocarbon-based polymers. Their respective characteristics for use in fuel cells are similar to Nafion membranes, but they are easier and cheaper to produce and recycle. An important parameter for these systems is the proton diffusion coefficient, since it is related to charge transfer across the membrane and removal of the resulting water. We investigated self-diffusion in a sulfonated co-polynaphthoylenimide proton exchange membrane using ¹H static field gradient (SFG) nuclear magnetic resonance (NMR). The polymer under study has a ratio of hydrophilic to hydrophobic groups of 60:40, and the saturation humidity of the samples varies from 31% to 100%. For this polymer, the magnetization transfer effects between protons in the membrane framework and water protons must be taken into account. To do this, we applied a model that accounts for such exchange phenomena and were able to determine the diffusion coefficients within a few percent uncertainty in the temperature range from 190 K to 365 K. We found a significant decrease in diffusion at low water concentrations and an increase in activation energy below 250 K, indicating a change in the diffusion mechanism.