Imidazolium-functionalized poly(arylene ether sulfone) block copolymer as an anion exchange membrane for alkaline fuel cell

An ethyl imidazolium-functionalized poly(arylene ether sulfone) (EI-PES) block copolymer was prepared as a novel anion exchange membrane. The EI-PES polymer was synthesized by polycondensation between the F- and OH-terminated oligomers, followed by benzylic bromination and imidazolium functionalization (homogeneous functionalization). The quaternary ammonium-functionalized PES (QA-PES) was also prepared by heterogeneous functionalization, and the properties were compared with EI-PES. The membrane obtained from EI-PES showed a well-defined phase separated morphology between hydrophobic and hydrophilic ionic units of the block copolymer. An IEC of 1.45 meq/g with hydroxide conductivity of 0.03 S/cm at r.t. was observed for EI-PES. The EI-PES membrane also displayed excellent dimensional, thermal, mechanical and chemical stabilities.