Preparation and investigation of various imidazolium-functionalized poly(2,6-dimethyl-1,4-phenylene oxide) anion exchange membranes

Imidazolium-type anion exchange membranes (AEMs) were prepared by functionalization of bromomethylated poly(2,6-dimethyl-1,4-phenyleneoxide) with six kinds of imidazole compounds, respectively, to investigate the correlation of the grafted imidazolium structure and the physicochemical properties of the membrane. The chemical structure of substituted groups in imidazolium cations would highly influence the ion exchange capacity, ionic conduction, mechanical strength, as well as stability in strong alkaline solutions of the AEMs. The membrane having C2-methyl and N3-butyl substituted groups in the imidazolium pendants exhibited superior properties among the prepared AEMs, i.e., an IEC of around 1.03 mmol g−1, hydroxide ion conductivity of 42.5 mS cm−1 at 80 °C, and tensile strength at break of 15.0 MPa, respectively. In addition, this membrane showed high alkaline stability and no obvious decline in conductivity was observed after being exposed to 1 M KOH at 60 °C for 180 h.