COMPOSITE POLYPYRROLE FILMS SWITCHABLE BETWEEN THE ANION-EXCHANGER AND CATION-EXCHANGER STATES

Catechol, hydroquinone, anthraquinone-2-sulfonate and melanin were inc orporated into a polypyrrole matrix during electropolymerization of py rrole. The concentration of quinones was adjusted such that composite films with mixed ion dynamics were formed. Part of the polypyrrole cat ionic groups was charge compensated by the negative charge of incorpor ated quinones, and part by anions from the electrolyte. These composit e polypyrrole films can be ''switched'' between a cation-exchanger sta te of the electrode at negative electrode potentials, and an anion-exc hanger state at more positive potentials by varying the potential. The same films can be also switched between a cation-exchanger state and an anion-exchanger state by varying the pH of the solution. The type o f ion dynamics in these films has been investigated by the EQCM techni que. Use of this technique allowed us to control the composition of pr epared films and to evaluate their relative doping level.