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Highly conductive anion exchange membranes based on one-step benzylation modification of poly(ether ether ketone)

Zhang, Zhenghui, Xiao, Xinle, Yan, Xin, Liang, Xian, Wu, Liang
Journal of membrane science 2019 v.574 pp. 205-211
anion-exchange membranes, benzylation, electrolytes, hydrogen, strength (mechanics), water uptake
Side-chain-type quaternized aromatic polyelectrolytes named QBz-PEEK-x have been synthesized via one-step benzylation modification of commercial poly(ether ether ketone) (PEEK). By controlling the molar ratio between the benzylation reagent and PEEK, the substitution degree x could be tuned in a wide range (51.1%~ 91.6%). A series of five anion exchange membranes (AEMs) with high mechanical strength were facilely prepared via solution-casting of QBz-PEEK-x. Water uptake, swelling ratio and ion conductivity of these AEMs were investigated in detail. Of particular interest is that, at 60 °C, the AEM of QBz-PEEK-76.0% exhibited a moderate water uptake of 56%, a low swelling ratio of 15%, and an exceptionally high OH– conductivity of 155 mS cm−1 which was comparable to the top values ever reported. Moreover, a promising peak power density of 391 mW cm−2 was achieved when assembling QBz-PEEK-76.0% AEM in a H2/O2 single cell operated at 70 °C. This unprecedented “benzylation” method opens a new door to novel high performance side-chain-type AEMs.