Anion conductive imidazolium-based Parmax alkaline membrane for fuel cell applications

The anion exchange polyphenylene membrane containing imidazolium hydroxide ionic functional group was synthesized by sequential chloromethylation, substitution with 1-methylimidazole and ion exchange. The imidazolium hydroxide Parmax 1200 membrane has all carbon-carbon bonds without ether linkages, which would be chemically strong. The polyphenylene structure of Parmax provides a stiff and resistant backbone, whereas the pendant benzoyl group provides sites for chemical modifications. The resulting ionomer membrane showed ion exchange capacity (IEC) of 2.14 mmol g^-1 with maximum chloromethylation yield. The imidazolium-functionalized copolymer membrane showed lower water affinity and high durability in alkaline condition. It exhibited hydroxide ion conductivity above 10^-2 S cm^-1 at room temperature and good chemical stability for up to seven days without significant losses of ion conductivity. The structural properties of the synthesized polymer membrane were investigated by ¹H NMR spectroscopy and FT-IR. The membranes were studied by IEC, water uptake, and conductivity assessment.