Quaternized poly (2,6-dimethyl-1,4-phenylene oxide) crosslinked by tertiary amine and siloxane for anion exchange membranes

A series of tertiary amine and siloxane crosslinked composite anion exchange membranes were prepared by incorporating 2-(3,4-epoxycyclohexyl) ethyltrimethoxysilane (EHTMS) and N , N , N ′, N ′-Tetramethyl-1,6-hexanediamine (TMHDA) into N -Methyldiethanolamine (MDEA)-functionalized poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) backbone via sol-gel process. The resultant membranes named as AEM-X (X = 1, 2, 3, 4), which own a three-dimensional (3D) cross-linking structure, exhibit superior swelling resistance, mechanical properties, even the thermal stability is up to 220°C. Compared with AEM-1 (contains no crosslinker), the swelling ratio of AEM-2 obviously decreases by 10.2% at 80°C, while the OH − conductivity of AEM-2 has a merely 1.9% decline (20.6 mS cm −1 ) at 80°C and can maintain 67% of its initial value in a 2 M aqueous NaOH at 80°C for 240 h. The simultaneous introduction of inorganic siloxane and organic linear crosslinker provides a new idea for the preparation of anion exchange membranes with largely improvement in dimensional stability and alkali resistance while the ionic conductivity is kept at comparatively high level.