Electron spin resonance measurements of Cu⁺⁺ distribution in cation exchange membranes

Electron spin measurement of the local Cu ++ concentrations have been performed in different cation exchange membranes by comparison with reference frozen aqueous solutions of Cu ++ salts. Comparison of the obtained values with the average chemical concentrations has therefore permitted direct evidence of microphase separation in these systems. Local concentrations approximately four times larger than average chemical concentrations have been found. Information about composition of this ion‐containing phase has also been obtained from changes in local Cu ++ concentrations versus water content.