COMPARISON OF ION-EXCHANGE PROPERTIES OF POLYPYRROLE WITH AND WITHOUTIMMOBILIZED DOPANTS BY OPTICAL BEAM DEFLECTION

The optical beam deflection technique (mirage effect) has been used si multaneously during cyclic voltammetry and chronoamperometry on two el ectrodeposited thin films in the presence of an aqueous solution of li thium perchlorate: one of polypyrrole and the other of poly{pyrrole-co -[4-(pyrrole-1-yl)-butane sulfonate]} which contains negatively charge d ionic groups attached to the polymeric chains. The expected behaviou r of an anionic exchange with the electrolyte for the polypyrrole film during the oxido-reduction is observed only for potentials more posit ive than the redox potential and a noticeable, but not constant, inter vention of cations is observed at lower potentials. For the modified p olypyrrole, it is the converse, the uniqueness of cation exchange is s een only for negative potentials below the peak, whereas the role of t he 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.