Effect of metal ion absorption on structure and electric conductivity of Nafion

Nafion film absorbing metal ions (Cu2+) was investigated by measuring small-angle X-ray scattering modified by an anomalous dispersion effect (ASAXS). ASAXS is a technique for revealing a distribution of a specific atom in nano-scale. When an incident X-ray energy was changed to 8331, 8960, 8970, 8980 and 8990eV in order to observe a distribution of Cu ion (Cu-K absorption edge: 8980eV), the change in the SAXS profiles was observed. After the analysis, it was revealed that the Cu ions gather in a domain of hydrophilic groups when solvent is water. Then, Nafion films with or without metal ions (Cu2+, Cu1+) were soaked in hydrogen peroxide at 70 degrees C for two weeks, and a structural change of these Nafion films was investigated by measuring standard small-angle X-ray scattering (SAXS). By comparing the SAXS profiles of Nafion with Cu ions to that without Cu ion, it was revealed that the structure of Nafion is changed by reaction of metal ions with hydrogen peroxide.