A Molecular Dynamics Study of Transport Properties in Degraded Nafion Membranes

In order to estimate the proton transport property of the degraded Nafion membrane, molecular dynamics simulations have been carried out. The degraded Nafion molecules are made by breaking side chains randomly. Degradation level is controlled by changing the number of broken side chains. In the simulation systems, there were four ten-unit degraded Nafion molecules and equimolar fragments generated by degradation in various conditions, such as different water contents and degradation levels. Density, diffusion coefficient, and number of water cluster have been evaluated. Our findings are, in the degraded Nafion membranes, water molecules and hydronium ions are more dispersed which suppresses Grotthus mechanism, and the system becomes much fluidity owing to the existence of various fragments which facilitates Vehicle mechanism.