Preparation and properties of novel cross-linked sulfonated poly(arylene ether ketone) for direct methanol fuel cell application

A series of cross-linkable sulfonated poly(arylene ether ketone)s bearing carboxylic acid groups (C-SPAEKs) have been prepared for direct methanol fuel cells (DMFCs). The chemical structure of the cross-linkable copolymers was analyzed by 1H NMR and 13C NMR spectra. Cross-linked membranes were obtained by thermal curing cross-linkable copolymers. The cross-linked network structure caused significant enhancement in the mechanical properties and large reduction in water uptake (WU), swelling ratio and methanol permeability of the membranes. The water uptake and methanol permeability of C-SPAEK-50 membrane was 506.9% (80 °C) and 14.83 × 10−7 cm2/s, but after cross-linking they reduced to 75.2% and 1.74 × 10−7 cm2/s, while maintaining proton conductivity of 0.197 S/cm, which was higher than 0.146 S/cm of Nafion 117.