Composite polypyrrole films switchable between the anion- and cation-exchanger states

Catechol, hydroquinone, anthraquinone-2-sulfonate and melanin were incorporated into a polypyrrole matrix during electropolymerization of pyrrole. The concentration of quinones was adjusted such that composite films with mixed ion dynamics were formed. Part of the polypyrrole cationic groups was charge compensated by the negative charge of incorporated quinones, and part by anions from the electrolyte. These composite polypyrrole films can be ''switched'' between a cation-exchanger state of the electrode at negative electrode potentials, and an anion-exchanger 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 of ion dynamics in these films has been investigated by the EQCM technique. Use of this technique allowed us to control the composition of prepared films and to evaluate their relative doping level.