Direct Imaging of Hydrated Polymer Electrolyte Membranes for Fuel Cell Applications

Ion conducting polymers containing sulfonic acid are of interest for the fuel cell applications. This study is based on sulfonated poly(styrene-b-methylbutylene) block copolymers. In dry state, these materials show remarkably rich sequence of phase transitions, i.e., lamellae, gyroid, hexagonally perforated lamellae, hexagonal cylinder, and disorder, depending on temperature, molecular weight, and fraction of sulfonated monomers. The effect of hydration on the dry morphologies is determined by a combination of in-situ neutron scattering and cryogenic electron microscopy.