IONIC-DIFFUSION AND ION CLUSTERING IN A PERFLUOROSULFONATE ION-EXCHANGE MEMBRANE

Tracer self-diffusion coefficients for Na+ and Cs+ have been measured in Nafion perfluorosulfonate ion-exchange membranes for three solvent systems: water, methanol, and acetonitrile. Results indicate that ion clustering exerts a pronounced effect on the diffusional properties of this material. Diffusion coefficients and activation energies of diffusion vary dramatically for small changes in swelling. This is attributed to changes in the ability of counterions to move between clusters. The ionic transport properties of Nafion are therefore very different from poly(styrenesulfonate) ion-exchange resins of similar swelling. © 1979 American Chemical Society.