Electrolyte membranes

The mesoscale structure of a hydrated electrolyte membrane (Nafion) in polymer electrolyte fuel cells is studied using dissipative particle dynamics (DPD). A polymer is modeled by coarse-grained particles, and interaction parameters for particles are estimated from the cohesive energy for each chemical species according to an atomistic simulation. In the dissipative particle dynamics simulation, a spongelike structure of the hydrophobic phase of the Nafion backbone spontaneously emerges from the initial condition of random dispersion; this structure matches that observed experimentally. The cluster size and its dependence on the water content are also in good agreement with experimental results for small-angle X-ray scattering. In addition, by considering molecular rigidity and shear flow, the current model explains the anisotropy in the swelling behavior observed in hydrocarbon-based electrolyte membranes in which the main chain skeletons are rigid.