Impact of hygrothermal aging on structure/function relationship of perfluorosulfonic-acid membrane

Impact of hygrothermal aging on structure/function relationship of perfluorosulfonic-acid membrane

TitleImpact of hygrothermal aging on structure/function relationship of perfluorosulfonic-acid membrane
Publication TypeJournal Article
Year of Publication2015
AuthorsShouwen Shi, Thomas J Dursch, Colin Blake, Rangachary Mukundan, Rodney L Borup, Adam Z Weber, Ahmet Kusoglu
JournalJournal of Polymer Science Part B: Polymer Physics
Volume54
Issue5
Pagination570-581
Date Published10/2015
Keywordsconductivity, degradation, films, hygrothermal aging, ion-exchange capacity, ionomers, molecular-origins, nafion membranes, pfsa ionomers, relative-humidity, saxs/waxs, structure/property, temperature, transport-properties, water
Abstract

Perfluorosulfonic-acid (PFSA) membranes are widely used as the solid electrolyte in electrochemical devices where their main functionalities are ion (proton) conduction and gas separation in a thermomechanically stable matrix. Due to prolonged operational requirements in these devices, PFSA membranes’ properties change with time due to hygrothermal aging. This paper studies the evolution of PFSA structure/property relationship changes during hygrothermal aging, including chemical changes leading to changes in ion-exchange capacity (IEC), nanostructure, water-uptake behavior, conductivity, and mechanical properties. Our findings demonstrate that with hygrothermal aging, the storage modulus increases, while IEC and water content decrease, consistent with the changes in nanostructure, that is, water- and crystalline-domain spacings inferred from small- and wide-angle X-ray scattering (SAXS/WAXS) experiments. In addition, the impact of aging is found to depend on the membrane's thermal prehistory and post-treatments, although universal correlations exist between nanostructural changes and water uptake. The findings have impact on understanding lifetime, durability, and use of these and related polymers in various technologies.

DOI10.1002/polb.23946
Short TitleJ. Polym. Sci. Part B: Polym. Phys.
Refereed DesignationRefereed