COMPARISON OF ION-EXCHANGE PROPERTIES OF POLYPYRROLE WITH AND WITHOUT IMMOBILIZED DOPANTS BY OPTICAL BEAM DEFLECTION

The optical beam deflection technique (mirage effect) has been used simultaneously during cyclic voltammetry and chronoamperometry on two electrodeposited thin films in the presence of an aqueous solution of lithium perchlorate: one of polypyrrole and the other of poly{pyrrole-co-[4-(pyrrole-1-yl)-butane sulfonate]} which contains negatively charged ionic groups attached to the polymeric chains. The expected behaviour of an anionic exchange with the electrolyte for the polypyrrole film during the oxido-reduction is observed only for potentials more positive than the redox potential and a noticeable, but not constant, intervention of cations is observed at lower potentials. For the modified polypyrrole, it is the converse, the uniqueness of cation exchange is seen only for negative potentials below the peak, whereas the role of the anion becomes observable for more positive potentials. Optical beam deflection allows a good identification of the uniqueness of the ion exchange or of the multiplicity along the potential exploration.