Environmentally friendly synthesis of alkaline anion exchange membrane for fuel cells via a solvent-free strategy

In this study, we described a solvent-free strategy for alkaline anion exchange membranes synthesis by in situ polymerization. Different from the available membrane synthesis by direct polymerization and post-polymerization modification, the non-solvent strategy demonstrated here was performed by dissolving brominated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO) in monomers mixture of vinylbenzyl chloride (VBC) and divinylbenzene (DVB) and then in situ polymerization to incorporate BPPO into the network of poly(VBC–DVB). After quaternization, a translucent, flexible and robust anion exchange membrane was obtained. The membrane morphology was confirmed by SEM-EDXA images. Factors such as quaternizing conditions and components of the casting solution were fully investigated. The optimized membranes exhibited favorable water uptakes (ranging from 19.9% to 29.3%) and hydrated hydroxyl conductivities (ranging from 0.017 to 0.028 S cm−1) at room temperature, which allows its application in alkaline anion exchange membrane fuel cells (AAEMFCs). Moreover, this solvent-free strategy is not limited to the above BPPO/VBC/DVB system. It can be applied to other compatible systems of (aromatic) polymers and (aromatic) monomers as long as homogeneous cast solution of the monomers and polymers can be formed. Thus this research will provide a versatile environmentally friendly route to prepare anion exchange membranes with tailored properties for alkaline fuel cells.