Interpenetrating network-forming sulfonated poly(vinyl alcohol) proton exchange membranes for direct methanol fuel cell applications

Poly (vinyl alcohol) was sulfonated and subsequently cross-linked by a thermal curing reaction with dual cross-linkers to prepare membranes for direct methanol fuel cells. Sulfonated poly (vinyl) alcohol (SPVA) with a high degree of sulfonation was synthesized from 4-Formylbenzene-1,3-disulfonic acid disodium salt hydrate via an acetalization reaction with PVA. Various masses of the cross-linking agents 1,3-bis(3-glycidyloxypropyl) tetramethyldisiloxane and 4,4′-oxydiphthalic anhydride were polymerized with SPVA to facilitate manipulation of the properties of the membranes. Notably, the SPVA3 showed excellent proton conductivity (cf. σ  = 0.218 S cm−1 at 70 °C and Nafion 117 = 0.127 S cm−1), and low methanol permeability (around one half of that Nafion 117). These results suggest that the cross-linked SPVA membranes hold promise as potential proton exchange membranes and given their high proton conductivity and low methanol permeability they may offer advantages when used in direct methanol fuel cells (DMFCs) applications.