State of Water in Perfluorosulfonic Ionomer (Nafion) Proton Exchange Membranes

This manuscript reports on the direct identification of four states of water in hydrated Nafion ionomer polymers, including a quantitative measurement of their dynamics, as previously published in the Journal of the Electrochemical Society, 155, B163-B171 (2008). Here, we provide further details on the dynamics of these water states and we underline still-open scientific questions, towards stimulating further fundamental research in the field.