Nafion is a sulfonated tetrafluoroethylene based fluoropolymer-copolymer discovered in the late 1960s by Walther Grot of DuPont. It is the first of a class of synthetic polymers with ionic properties which are called ionomers. Nafion's unique ionic properties are a result of incorporating perfluorovinyl ether groups terminated with sulfonate groups onto a tetrafluoroethylene (Teflon) backbone. Nafion has received a considerable amount of attention as a proton conductor for proton exchange membrane (PEM) fuel cells because of its excellent thermal and mechanical stability.
The chemical basis of Nafion's superior conductive properties remain a focus of research. Protons on the SO3H (sulfonic acid) groups "hop" from one acid site to another. Pores allow movement of cations but the membranes do not conduct anions or electrons. Nafion can be manufactured with various cationic conductivities.
Read more about Nafion: Nomenclature and Molecular Weight, Preparation, Properties, Structure/morphology, Applications, Modified Nafion For PEM Fuel Cells