Physical properties and application of conducting polypyrrole-silica glass composite films prepared by electrochemical polymerization

Conducting polymers with extensive a-electron delocalization are intensively studied as materials in the field of electronics and optics. Polypyrrole, PPy, can be readily produced by electrochemical procedures and are attractive because of their good environmental stability and relatively high electrical conductivity. Until now, most synthesis work has focused on the use of organic solvent systems with relatively little attention having been paid to aqueous systems. However, it was recently found that PPy prepared electrochemically in aqueous solutions also possesses high electrical conductivity. Further, improvements of processability, mechanical property, and stability in atmospheric environment for the conducting polymer have also been made by forming polymer-polymer composites. On the other land, the sol-gel process offers new approaches to the synthesis of oxides materials. Starting from molecular precursors such as metal alkoxides, an oxide network is obtained via inorganic polymerization reactions. A lower temperature processing allows the synthesis of metastable oxide phases or even mixed organic-inorganic materials. In our laboratory, it has been found that the conducting PPy-silica glass composite films can be simply prepared by carrying out the electrochemical polymerization of PPy simultaneously with the synthesis of silica glass by using the sol-gel processing. In this paper, the electro chemical behavior of the exchange process for dopant anions in PPy-silica glass composite film was investigated by means of cyclic voltammetry. That is, with decreasing a size of dopant anion, PPy-silica glass composite films showed a tendency of increasing in their kinetics of electrochemical reaction during repetitive potential sweep cycles. These learning phenomena are attributable to enhancement of diffusion coefficients of dopant anions caused by structural changes of the polymer layers during dope undope cycles. Application of these new type of PPy-silica glass c- mposite films to the ionic sensor which responds to specific ions has also been proposed.