Impact of Dispersion Solvent on Ionomer Thin Films and Membranes

Impact of Dispersion Solvent on Ionomer Thin Films and Membranes

TitleImpact of Dispersion Solvent on Ionomer Thin Films and Membranes
Publication TypeJournal Article
Year of Publication2020
AuthorsSarah A Berlinger, Peter J Dudenas, Ashley Bird, Xunkai Chen, Guillaume Freychet, Bryan D McCloskey, Ahmet Kusoglu, Adam Z Weber
JournalACS Applied Polymer Materials
Volume2
5824
Issue12
Pagination5824 - 5834
Date Published11/2020
ISSN2637-6105
Abstract

Perfluorosulfonic acid (PFSA) ionomers are an important class of materials that many electrochemical devices rely on as their ion-conducting electrolyte. Often, PFSA films are prepared through solution-processing techniques. Previous research has demonstrated that the solvent environment affects PFSA dispersion conformation, but it is not clear to what extent (if at all) these conformational effects persist for thin films and membranes upon casting, nor how dispersion solvent impacts film formation during the drying process. Here, we explore these questions by systematically examining the effect of water and n-propanol mixtures on PFSA thin-film formation and structure, membrane structure, and resulting properties. Using a combination of in situ, time-resolved grazing incidence X-ray scattering and tender wide-angle X-ray scattering, it is shown that films prepared from high-water-concentration dispersions exhibit stronger interactions and arrangement upon drying, and possess larger network domain sizes than those prepared from low-water-concentration dispersions. These stronger interactions likely manifest in greater network connectivity, as evidenced by enhanced conductivity for membranes and decreased water uptake for thin films. Significantly, these solvent-induced differences persist even after thermal annealing. It is clear that the dispersion solvent choice is a critical parameter controlling PFSA nano- and mesoscale structure and presents an important dial with which to direct PFSA macroscale properties.

DOI10.1021/acsapm.0c0107610.1021/acsapm.0c01076.s001
Short TitleACS Appl. Polym. Mater.
Refereed DesignationRefereed