Different properties of the polymer electrolyte membranes (PEMs), like proton conductivity, ion exchange capacity, methanol permeability, water content and thermal stability, were examined as a function of solvent type, casting temperature and membrane post-treatment.
The membrane cast using dimethyl sulphoxide (DMSO) as solvent, at higher temperature (45 掳C vs 30 掳C) and with acid post-treatments, resulted to be more conductive. It was found that polymer-solvent interactions play a determining role on the PEM microstructural organization and, as a consequence, on the proton transport pathway. The electrochemical properties of the PEMs are indeed closely related to their microstructure, especially the spatial distribution and nature of their ionic sites. The DMSO use as solvent increased also the thermal stability of the membranes (higher decomposition temperature of the sulphonic groups).