Composite membranes for proton exchange membrane fuel cells based on methyl methacrylate-co-maleimide /phosphotungstic acid

Poly(methyl methacrylate-co-nitrophenyl maleimide) (MMA-co-NMI) and poly(methyl methacrylate-co-hydroxyphenyl maleimide) (MMA-co-HMI) copolymers were synthesized using free radical polymerization of MMA with a new MI monomer containing phenyl and –NO2 groups. Proton exchange membrane fuel cell(PEMFC) were prepared using these copolymers as membrane matrix and phosphotungstic acid (PWA) as proton conductive additive. Dry-phase inversion method was employed to fabricate membranes with different concentrations of copolymers and PWA. Characteristics and proton conductivity of membranes were investigated using FTIR, SEM, TGA, DTG, DSC, ion exchange capacity, water uptake, and proton conductivity tests. Results revealed an increment in the thermal stability as well as ion exchange capacity of composite membranes prepared by addition of PWA. Moreover, applying MMA-co-HMI as copolymer and PWA as additive remarkably improved the proton conductivity of membrane (2.6×10−1 S.cm−1) due to the interaction between the functional groups of PWA (H3O+ ions, O atoms) and MMA-co-HMI copolymer (OH, C=O functional groups).