High-performance anion exchange membranes achieved by crosslinking two aryl ether-free polymers: poly(bibenzyl N-methyl piperidine) and SEBS

Poly(aryl piperidinium) (PAP), the aryl ether-free polymer backbone, has drawn recent attention as a high-performance anion exchange membrane (AEM) material due to its excellent ion-conduction and alkaline stability. However, the relatively low mechanical (strain) property and poor phase separation of these PAP-based membranes require further improvement. Thus, this study crosslinked the poly(bibenzyl N-methyl piperidine) (PBB), a rigid PAP unit, with poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS), an elastic unit. Crosslinked PBB-SEBS membranes were prepared with different rigid and elastic polymer ratios by tuning the crosslinking degree. The membrane with a crosslinking degree of 40% exhibited a high elongation at break, 70.3%, a high Young's modulus, 486 MPa, and very high ionic conductivity (72.28–146.25 mS cm−1) from the high bound water content and the optimized morphology. Furthermore, it exhibited excellent alkaline (99% conductivity remaining for 720 h, 2 M KOH, 80 °C) and oxidative stability (98% for 120 h, 60 °C). With the highest RH and normalized conductivity in water, the membrane showed peak power density of 555 mW cm−2 in an AEM fuel cell test and a current density of 1042 mA cm−2 at 1.8 V, 178% of the value of the commercially available FAA-3-50, in the AEM water electrolysis test.