Methods of making anion exchange membrane via simultaneous post-functionalization and crosslinking of epoxidized sbs

Abstract

An anion exchange membrane is provided by converting carbon-carbon double bonds in the backbone of polystyrene-block-polybutadiene-block-polystyrene (SBS) into epoxide groups. Unmodified SBS is first partially hydrogenated to remove about 65% to about 90% of carbon-carbon double bonds. The remaining double bonds are then converted to epoxide groups to form an epoxidized SBS. UV-initiated ring opening reactions between the epoxidized SBS and haloalkyloxiranes are then employed to simultaneously functionalize and crosslink the epoxidized SBS. The halide groups in the crosslinked polymer network can be replaced via nucleophilic substitution to offer anion conductivity, e.g., via reaction with trimethylamine. Further ion exchange reactions can then be performed to make the membrane hydroxide conductive. The crosslinked membranes described herein exhibit a mechanical strength improvement of 200% compared to unmodified SBS, while maintaining high hydroxide conductivity. This synthetic platform is advantageous to provide mechanically robust anion exchange membranes for fuel cell applications.