Side-chain-type anion exchange membranes bearing pendent imidazolium-functionalized poly(phenylene oxide) for fuel cells

• Novel side-chain-type AEMs were prepared under mild condition.
• The synthesis avoids the use of toxic chloromethyl methyl ether.
• The AEMs exhibit a highest conductivity of 78.8 mS cm−1 at 80 °C.
• The AEMs have high thermal stability and reasonable alkaline stability.
• The AEMs have high water uptake and swelling at 80 °C.

A series of novel side-chain-type anion exchange membranes (AEMs) composed of poly (arylene ether sulfone)s backbone and pendent imidazolium-functionalized polyphenylene oxide (PPO) was prepared via chemical grafting, bromination, functionalization and alkalization. The chemical structure of the as-synthesized copolymers was confirmed by 1H NMR spectroscopy. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the morphology of the AEMs. The densely functionalized side chains are found to be beneficial to the formation of ion clusters, as demonstrated by TEM. As a result, the hydroxide conductivity of the PAES-x-IMPPO membranes was 78.8 mS cm−1 at 80 °C. Moreover, the AEMs also exhibit robust mechanical properties, good thermal stability and reasonable alkaline stability. An open circuit voltage (0.98 V) of H2/O2 alkaline fuel cell using PAES-15-IMPPO at 60 °C can be an indicative of low fuel crossover. The maximum power density was 56.8 mW cm2 at a current density of 125 mA cm2 without optimization.

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