Reinforced Polymer Blend Membranes with Liposome-Like Morphology for Polymer Electrolyte Membrane Fuel Cells Operating under Low-Humidity Conditions

Abstract

Reinforced polymer blend membranes with liposome-like morphology prepared for applications in polymer electrolyte membrane fuel cells from a sulfonated poly(ether sulfone) (BPSH), a hydroxylated poly(ether sulfone), and a hydroxylated sulfonated poly(ether sulfone) as a compatibilizer are characterized both experimentally and theoretically (by mesoscale and molecular dynamics simulations). Compared with those prepared from pristine BPSH, blend membranes exhibit improved mechanical strength, lower water uptake, and better dimensional stability, which is ascribed to the presence of hydroxylated polymers and the resulting hydrogen bonding between polymer chains. The blend membranes also show unusual morphologies; e.g., the 60-811 membrane exhibits a unique nanoscale phase-separated morphology similar to that of a liposome, featuring hydrophilic spherical ionic clusters (0.5 mu m) with the small ionic domains of 15-20 nm at their cores. Hydrogen bonding between hydroxyl groups and sulfonic acid groups in this membrane results in enhanced water retention capability, high proton conductivity, and excellent single-cell performance superior to that of Nafion 212 under the conditions of both full and insufficient hydration.