CONDUCTIVITY DEGRADATION IN OXYGEN-AGED POLYPYRROLE

The conductivity of doped polypyrrole, as high as 100 Scm-1 in freshly prepared samples, falls slowly with time on exposure to atmospheric oxygen. Typically, the fall in conductivity is fairly slow at room temperature, but the process can be accelerated by heating samples and measuring the decrease in conductivity as a function of time. Analysis of the kinetics of this process shows a preliminary, 120 min regime in which a surface adsorption-diffusion mechanism with an activation energy of 0.41 eV appears to mediate. Once a degree of adsorbate saturation is attained subsequent behavior is well described by standard bulk diffusion considerations and is activated at 0.48 eV. We propose a mechanism whereby oxygen adsorption onto the surfaces of the polymer fibrils and diffusion into the interior are respective rate limiting steps in the incorporation of oxygen into the closely cross-linked mesh, blocking conducting pathways.