Anion conductive aromatic membrane of poly(tetra phenyl ether sulfone) containing hexa-imidazolium hydroxides for alkaline fuel cell application

Anion exchange membranes of poly(tetra phenyl ether sulfone) containing hexa-imidazolium hydroxides on the hydrophilic segment of a polymer unit were synthesized by sequential polycondensation, chloromethylation, substitution with 1-methylimidazolium and ion exchange. They showed elevated molecular weight, high solubility in polar aprotic solvents and strong chemical and thermal stabilities in comparison to alkyl quaternary ammonium-functionalized polymers. Different levels of substitution and ion exchange were tested; the resulting ionomer membranes showed high ion exchange capacities (IECs) of up to 2.41 mmol g− 1. The imidazolium-functionalized copolymer membranes showed lower water affinity and high durability in alkaline condition. They exhibited hydroxide conductivity above 10− 2 S cm− 1 at room temperature and good chemical stability for up to 7 days without significant losses of ion conductivity.