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Anion Exchange Ionomers: Impact of Chemistry on Thin‐Film Properties
Author(s) -
Luo Xiaoyan,
Kushner Douglas I.,
Li Jonathan,
Park Eun Joo,
Kim Yu Seung,
Kusoglu Ahmet
Publication year - 2021
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.202008778
Subject(s) - ionomer , thin film , materials science , quartz crystal microbalance , membrane , ion , chemical engineering , nanotechnology , chemical physics , polymer , chemistry , organic chemistry , composite material , adsorption , biochemistry , engineering , copolymer
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.