Hybrid sol–gel–conducting polymer synthesised by electrochemical insertion: tailoring the capacitance of polyaniline

Abstract

The templated growth of polyaniline through porous sol–gel films on ITO substrates has been performed. The polyaniline–silica composites have been synthesized by electrochemical reactive insertion in potentiodynamic and potentiostatic conditions. When the polymer is synthesized by potential step experiments, the shape of the chronoamperograms indicates two regimes for the electrochemical polymerization of PANI. Electropolymerization happens faster within the silica pores than on bare ITO electrodes due to confinement effects of oligomeric species formed upon oxidation. The electrochemical capacitance of the silica–PANI hybrids is several time higher than the capacitance of ITO/PANI synthesized under the same conditions. The silica matrix avoids the electric collapse between vicinal conducting fibres in ITO/silica–PANI but allows the diffusion of ionic species that are in contact with the conjugated polymer, increasing therefore the conducting surface exposed to the electrolytic solution.