Anion Exchange Ionomers: Impact of Chemistry on Thin‐Film Properties

Anion Exchange Ionomers: Impact of Chemistry on Thin‐Film Properties

TitleAnion Exchange Ionomers: Impact of Chemistry on Thin‐Film Properties
Publication TypeJournal Article
Year of Publication2021
AuthorsXiaoyan Luo, Douglas I Kushner, Jonathan Li, Eun Joo Park, Yu Seung Kim, Ahmet Kusoglu
JournalAdvanced Functional Materials
Pagination2008778
Date Published03/2021
ISSN1616-301X
Abstract

Ionomer thin‐films (i.e., 20–100 nm) on supports serve as model systems to understand ionomer‐catalyst interfacial behavior as well as the confinement‐driven deviation in properties from bulk membranes. While ionomer thin‐films have been examined for proton exchange ionomers, the thin‐film properties of anion exchange ionomers (AEIs) remain largely unexplored. More importantly, delineating the convoluted impact of chemistry and confinement on thin‐film morphology and hydration is of interest to advancing the field on functional ionic interfaces. In this work, these aspects are studied by using AEIs of different backbones (perfluorinated, aliphatic, and aromatic) and side chains (various lengths, and single versus dual functional groups). Quartz‐crystal microbalance and spectroscopic ellipsometry are used to analyze density and coupled with calculated free volume fraction of thin‐films to provide insights on their gas transport properties. AEI side‐chain's chemical character plays a key role in how confinement modulates hydration (in thin‐film versus bulk). The results elucidate the effects of backbone, side‐chain chemistry versus anion/cation type in the confinement‐driven changes in thin‐film morphology and swelling. This study also provides new insights for tuning AEI transport functionalities at interfaces via chemistry, which can benefit the design and development of electrode‐ionomers for alkaline membrane‐based energy systems.

DOI10.1002/adfm.202008778
Short TitleAdv. Funct. Mater.
Refereed DesignationRefereed