Ionic diffusion across oxidized polypyrrole membranes and during oxidation of the free-standing film

In this work, we approach the study of the ion transport across a new free-standing polypyrrole (ppy) film measuring the ionic conductivity of the film working as a membrane in a diffusion cell. From these measurements, the diffusion coefficient of ions across the film is estimated and compared with those diffusion coefficient determined by chronoamperometric oxidation of the conducting polymer under anodic polarisation. For a particular electrolyte concentration and temperature, the membrane ionic conductivity depends on the oxidation degree of the film, which points to the control of membrane selectivity by the oxidation deep and suggests possible applications of these films as smart ion exchange membranes. For certain electrolyte concentration, the diffusion coefficient across the film is one order of magnitude lower than those obtained by oxidative processes of the free-standing polypyrrole film. The diffusion coefficient of such oxidative processes is also one order of magnitude higher than that reported in the literature for a thinner ppy film supported on a metallic electrode. (c) 2005 Elsevier B.V. All rights reserved.