Elaboration and electrical characterization of silicone-based anion-exchange materials

Ion exchange phenomena have been investigated in a polymeric anion-exchange membrane prepared from cross-linked silicone polymer grafted with cationic groups. The affinity of different anions towards the membrane was inferred from impedance measurements in a electrolyte/insulator/semiconductor (EIS) electrochemical set up, allowing the survey of the detection limit, flat band potential and capacity variations. The selectivity of ion-exchange for a series of anions having a the same electrical charge followed the Hofmeister series. It was found that the affinity of anions and the electrical potential variations were related because the anion exchange inside the bulk of the membrane was correlated with the adsorption of anions at its surface. Electrical capacity measurements gave supplementary information which was difficult to rationalize because they depended on several parameters.