Olefin metathesis-crosslinked, bulky imidazolium-based anion exchange membranes with excellent base stability and mechanical properties

To improve the mechanical properties of anion exchange membranes (AEMs) with bulky imidazolium cations, a series of anion-conductive poly(2,6-dimethyl-phenylene oxide)s (PPO)s with crosslinkable terminal double bonds were synthesized by the Menshutkin reaction. Following crosslinking via olefin metathesis at room temperature catalyzed by a Grubb's second generation catalyst, tough, transparent, and flexible PPO-based AEMs were obtained. The crosslinked AEMs exhibited good mechanical properties (tensile strength at maximum load of 20.8–49.9 MPa and values of elongation at break of 1.5–3.0%) though their bulky imidazolium cation groups which could destroy the film-forming ability of polymer. And the obtained mechanical properties were considerably better than those of the non-crosslinked AEMs with a similar architecture, which broke into small pieces during the process of membrane fabrication using solvent casting. Furthermore, the crosslinked AEMs exhibited an extremely low water uptake (up to 13.9 wt% at 80 °C) and minimal swelling (