NafionTM is a polymer based on PTFE (polytetrafluoroethylene) made by the Dupont company. Sulphonated fluoropolymers like Nafion have side chains added to the 'backbone' structure of the polymer. The sulphonate groups cluster together and water collects around the ionised groups when the membrane is saturated. Within these hydrated regions the hydrogen ions of the sulphonic acid groups can move freely. This enables the membrane to transfer protons rapidly from one side of the membrane to the other. Link
