Anion conductive poly(arylene ether sulfone)s containing tetra-quaternary ammonium hydroxide on fluorenyl group for alkaline fuel cell application

A series of poly(arylene ether sulfone)s containing tetra-quaternary ammonium hydroxide on fluorenyl group (QAPAES-OH) were synthesized via polycondensation, chloromethylation, quaternization, and the subsequent ion exchange reactions. The tetra-quaternary ammonium hydroxide polymers rendered an elevated molecular weight and exhibited an outstanding solubility in aprotic polar solvents. Consequently, flexible and tough alkaline membranes with varying ionic contents were obtained by an anion exchange of tetra-quaternary ammonium chloride polymers with 1.0 M KOH at room temperature. Quaternization and the following ion exchange reactions were quantitative so that the obtained ionomer membranes could have high ion exchange capacity (IEC) upto 1.73 mmol g−1. High hydroxide ion conductivity was achieved up to 30.7 mS cm−1 at 80 °C with the membrane of the highest IEC. The resulting polymers were characterized by 1H NMR, FT-IR, and TGA.