Improved conductivity and stability of anion exchange membranes by introducing steric hindrance and crosslinked structure

The alternating copolymer based on poly (ether ether ketone) (PEEK) is synthesized with ordered side chain. A series of novel anion exchange membranes grafte with the 1, 2-dimethylimidazole and 1-vinylimidazole are obtained. The copolymer was verified by 1H NMR and the crosslinked membranes are further investigated by solvability test. The ordered hydrophilic side chains form well-defined microphase separation structure, which are proved by Transmission electron micrographs microscopy (TEM). The ionic conductivity is 0.075 S/cm at 80 °C of Im-PEEK-0 uncross-linked membrane. With the addition of 1-vinylimidazole, the maximum stress increases to 66.57 MPa, the water uptake drop to 17.1% and swelling ratio drop to 14.8% at 80 °C of Im-PEEK-0.3 membrane. The hydroxide conductivity remains 82.8% in 2 mol L−1 NaOH solution at 60 °C for 400 h. Meanwhile, all the membranes exhibit excellent thermal stability. Overall, the ordered imidazolium-functionalized side chains provide a method to balance hydroxide conductivity and alkali stability of anion exchange membranes.