Evaluation of carboxylic, phosphonic, and sulfonic acid protogenic moieties on tunable poly(meta-phenylene oxide) ionomer scaffolds

A tunable, meta-linked aryl ether polymer scaffold enables the introduction of various acid groups for a fundamental comparison of their contributions to proton conduction. Sulfonic acid-functionalized polymers offer the best proton conduction at low temperature and high relative humidity, while phosphonic acid-functionalized polymers outperform sulfonic and carboxylic acid-derived polymers at high temperature or low humidity.