Anion exchange membranes prepared from quaternized polyepichlorohydrin cross-linked with 1-(3-aminopropyl)imidazole grafted poly(arylene ether ketone) for enhancement of toughness and conductivity

A novel anion exchange membrane was synthesized via crosslinking of the quaternized polyepichlorohydrin (QPECH) by 1-(3-aminopropyl) imidazole grafted poly(arylene ether ketone) (PAEK-API). While the QPECH provided an excellent ion conductive property, the rigid rod-structured PAEK-API played a reinforcing role, along with providing the high conductivity associated with the pendant API group. The chemical structure of QPECH/PAEK-API membranes was identified by¹ H nuclear magnetic resonace spectroscopy. A variety of membrane properties, such as anion conductivity, water uptake, length swelling percentage, and thermal, mechanical and chemical stability, were investigated. The QPECH/PAEK-API1 membrane showed quite high hydroxide ion conductivity, from 0.022 S cm⁻¹ (30^◦ C) to 0.033 S cm⁻¹ (80^◦ C), and excellent mechanical strength, associated with the low water uptake of less than 40%, even at 80^◦ C. Such high conductivity at relatively low water uptake is attributed to the concentrated cationic groups, in a cross-linked structure, facilitating feasible ion transport. Further, the QPECH/PAEK-API membranes showed thermal stability up to 250^◦ C, and chemical stability for 30 days in a 4 NaOH solution, without significant loss of ion exchange capacity.