Cross-linked Poly(arylene ether ketone) proton exchange membranes with high ion exchange capacity for fuel cells

Sulfonated poly(arylene ether ketone) (SPAEK) possessing the pendant carboxylic acid groups was synthesized. The carboxylic acid groups of SPAEK were reacted with a cross-linking reagent to prepare a cross-linked membrane with a high ion exchange capacity (IEC), a high oxidative stability, and an excellent mechanical strength. The cross-linking hindered the mobility of the polymer chains and thus strongly affected the water uptake and the methanol permeability of the membranes. Also, as the cross-linker used in this study bore sulfonic acid groups, cross-linking did not lead to a noticeable loss of the proton conductivity. The cross-linked SPAEK membrane with 20% cross-linking density, CSPAEK-20% membrane, exhibited a high proton conductivity of 0.045Scm ^-1 associated with a high IEC value of 1.78mmolg ^-1 but a low methanol permeability of 4.3×10 ^-7cm ²s ^-1. The CSPAEK-20% membrane also showed excellent cell performance and oxidation resistance.