Dynamics of iron and europium in Nafion polymer membranes

Mossbauer spectral studies of Fe2+ and Eu3+ in Nafion polymer membranes in the temperature range between 90K and 250K have been performed. Above a critical temperature (∼180K) the spectra show a sharp decrease in the f-factor. Both the iron and europium spectra contain elastic narrow and quasielastic broad absorption lines, which are typical of bounded diffusion phenomena observed in biopolymers. The results are interpreted in terms of bounded diffusive motion of the metal ion using a model based on overdamped harmonically bound Brownian motion. The temperature dependence of the f-factor changes with the amount of water contained in the polymer.