Proton-Conducting Interpenetrating Polymer Network with Reduced Methanol Permeability

A freestanding polymer electrolyte membrane was developed having low permeability to methanol while maintaining high permeability to water and proton conductivity. A two-polymer composite formed an interpenetrating polymer network (IPN) composed of proton-conducting 2-acrylamido-2-methyl propanesulfonic acid and a second polymer, poly(vinyl alcohol), serving as a methanol barrier. Ion conductivity and methanol permeability were controlled by adjusting polymer ratios and the extent of cross-linking of the two polymers. Compared to Nafion, the IPNs had up to fifteen times greater selectivity for water over methanol and proton conductivity about an order of magnitude lower.