Stability of chemically synthesized polypyrrole films

Abstract

Polypyrrole powders and films deposited on various fabrics are chemically synthesized by reaction of FeCl 3 with pyrrole in an aqueous solution containing an optional sulfonate dopant ( p-toluenesulfonate or 2-naphthalenesulfonate). Two synthesis processes are used and the resulting materials are compared. Electrical conductivities are measured, doping levels are determined by neutronic activation and dedoping phenomena are appreciated by evolved-gas analysis. Ageing experiments in ambient air at various temperatures are performed and conductivity decays are measured in situ for kinetic studies. These materials present good conductivities (120 S/cm) or area resistivities (5 μ/ξ) due to the preferential incorporation of the sulfonate in the polymer. Our best films exhibit higher stability than electrochemical samples (evaluated t 1 2 =2800 days at ambient temperature) in relation with a high thermal activation of the conductivity decay ( E a=20 kcal/mol). The conductivity decay of these films appears to follow a diffusion-controlled kinetics. This diffusion phenomenon appears to be solid state diffusion ( D=10 −18−10 −17 cm 2/s). Polypyrroles doped with 2-naphthalenesulfonate are found to be more stable than samples doped with the usual p-toluenesulfonate.