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Anion exchange membranes based on quaternary ammonium-functionalized poly(ether sulfone ketone) block copolymers (QA-PESK) with various hydrophilic–hydrophobic oligomer block ratios (10:7, 10:18, and 10:26) were synthesized, and the block length effect on the membranes' physicochemical and electrical properties were systematically investigated. The QA-PESK-10-18 membrane, prepared using a hydrophilic and hydrophobic block ratio of 10:18, displayed well-balanced hydrophilic/hydrophobic phase separation, the highest conductivity of 23.19 mS cm−1 at 20 °C and 57.84 mS cm−1 at 80 °C, and the highest alkaline stability among the three block ratios tested, indicating that the membranes' properties were closely related to their morphologies, which were determined by the hydrophilic/hydrophobic ratio of the block copolymer. The H2/O2 single cell performance using the QA-PESK-10-18 revealed a maximum power density of 235 mW cm−2.

A series of poly(meta/para-terphenylene-methyl piperidinium)-based anion exchange membranes devoid of benzylic sites or aryl ether bonds, that are vulnerable to degradation by hydroxide ions, are synthesized and investigated for their application as novel anion exchange membranes. The copolymers are composed of both linear para-terphenyl units and kink-structured meta-terphenyl units. The meta-connectivity in terphenyl units permits the polymer backbones to fold back, maximizing the interactions among the hydrocarbon polymer chains and enhancing the peripheral formation of ion aggregates, due to the free volume generated by the kink structure. The effects of the copolymer composition between para-terphenyl and meta-terphenyl on the morphology and the electrochemical and physicochemical properties of the corresponding polymer membranes are investigated.

Crosslinked poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) using hydrophilic crosslinkers that contain ethylene oxide (EO) were prepared as novel anion exchange membranes (AEMs), and the effect of crosslinker EO length was systematically investigated. The physicochemical, morphological and electrochemical properties of the corresponding AEMs were also compared against the membrane prepared from a typical hydrophobic alkyl-type crosslinker. The ethylene oxide crosslinker helped to form ion clusters and to enhance the water-holding capacity of the corresponding AEMs, which promoted high conductivity both in water and in 95% room humidity conditions, whilst maintaining high physicochemical stability. However, it was also found that the presence of a long ethylene oxide as a crosslinker may induce polymer crystallinity, which reduces both conductivity and the alkaline stability of the corresponding crosslinked membranes. The effect of ethylene oxide chain length on the morphology, electrochemical and physicochemical properties, were also investigated. The xBEO-PPO membrane, having bis(ethylene oxide) (BEO) as a crosslinker, showed the highest conductivity of 131.96 mS/cm in water at 80 °C, and 55.21 mS/cm in 95% RH at 80 °C; this was owing to its crystalline nature. The single-cell performance of 444 mW/cm2 peak power density, was also obtained from the xBEO-PPO membrane.