Taehoon Hong

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.