Preparation and characterization of crosslinked sulfonated poly(ether ether ketone) membranes using 4-vinylbenzyl chloride via electron beam irradiation and subsequent Friedel-Craft reaction

In general, excessive water uptake of highly sulfonated aromatic hydrocarbon membranes limits their use in the fabrication of polymer electrolyte membrane fuel cells (PEMFCs). In this study, sulfonated poly(ether ether ketone) (SPEEK) was successfully crosslinked using 4-vinylbenzyl chloride as a crosslinking agent via electron beam (EB) irradiation and subsequent Friedel-Craft reaction. The crosslinking process significantly reduced the water uptake and methanol permeability of the SPEEK membranes, and greatly improved their dimensional stability and mechanical strength, although with a slight reduction in elongation at break. The process reduced the proton conductivity of the SPEEK membranes, but the proton conductivities of the crosslinked SPEEK membranes remained comparable to that of Nafion 212. The study results demonstrated the potential of the proposed crosslinking procedure to overcome excessive water uptake-induced problems of highly sulfonated aromatic hydrocarbon membranes.