ELECTROCHEMICAL PROPERTIES OF POLYPYRROLE FILMS POLYMERIZED IN THE PRESENCE OF METHYLENE-BLUE

The electrochemical properties of polypyrrole (PPy) electropolymerized in 0.1 M KCl solution containing Methylene Blue (MB) are investigated . It is found that a large amount of Methylene Blue is incorporated in the film during the electropolymerization process, which indicates th at the Methylene Blue cation plays a role in the film formation proces s. In strong acidic medium, two redox processes are observed in cyclic voltammograms of the film, corresponding to the redox couples of PPy and MB, respectively. The redox potential of the incorporated MB depen ds on the pH of the electrolyte solutions and a highly stable and reve rsible cyclic voltammogram is obtained at pH values lower than 2.0. In neutral or alkaline medium, the redox waves of MB are overlapped by t he waves of PPy and the electrochemical behaviour of the film is simil ar to that of normal PPy films doped with chloride. However, a more pr onounced relaxation behaviour of the film is obtained and a logarithmi c law for the shifts of the anodic peak parameters as a function of wa iting time in the insulating state is observed. Electrochemical impeda nce spectra clearly show two charge transfer processes in the film. Th e electroactivity of the polymer films is also investigated with respe ct to the ionic nature of the electrolytes. The results indicate that the redox process of MB is mediated by PPy and can only occur when PPy is in its oxidized state.