Comparison of properties of anion conductive Parmax membranes containing imidazolium cation and quaternary ammonium

Abstract The hydroxide conductive polyphenylene membranes were synthesized by sequential chloromethylation, substitution with 1-methylimidazole, quaternization with trimethylamine and ion exchange. The alkaline Parmax 1200 membranes have all carbon–carbon bonds without ether linkages, which would be chemically strong. The polyphenylene structure of Parmax provides a stiff and chemical-resistant backbone, whereas the pendant benzoyl group provides sites for chemical modifications. The resulting ionomer membranes showed ion exchange capacities (IECs) of 2.14 mmol g −1 for imidazolium functionalized and 2.36 mmol g −1 for quaternary ammonium. The imidazolium-functionalized copolymer membrane showed lower water affinity and high durability in alkaline condition compared to that of quaternary ammonium. Both of the membranes 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 1 H NMR spectroscopy and FT-IR. The membranes were studied by IEC, water uptake, dimensional stability, atomic force microscopy (AFM), and also conductivity assessment.