An inventory of physicochemical methods was drawn up, including both analytical and macromolecular techniques. Various chemical and spectroscopic analyses provide accurate determination of the cationic exchange capacity (CEC) and enable appropriate methods to be selected in order to obtain rapid and precise information about ionomers. Macromolecular characterizations, i.e. macromolecular weight distribution and ramifications are essential. In the context of our study, they allowed the degradations of polymer skeleton occurring during sulfonation to be observed both at the laboratory and pilot scales. This set of characterizations should enable optimization of both the performance and the lifespan of membranes designed for proton exchange membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFC) energy sources. (c) 2006 Elsevier Ltd. All rights reserved.