STABILITY OF CHEMICALLY SYNTHESIZED POLYPYRROLE FILMS

Polypyrrole powders and films deposited on various fabrics are chemica lly synthesized by reaction of FeCl3 with pyrrole in an aqueous soluti on containing an optional sulfonate dopant (p-toluenesulfonate or 2-na phthalenesulfonate). Two synthesis processes are used and the resultin g materials are compared. Electrical conductivities are measured, dopi ng levels are determined by neutronic activation and dedoping phenomen a are appreciated by evolved-gas analysis. Ageing experiments in ambie nt air at various temperatures are performed and conductivity decays a re measured in situ for kinetic studies. These materials present good conductivities (120 S/cm) or area resistivities (5 OMEGA/square) due t o the preferential incorporation of the sulfonate in the polymer. Our best films exhibit higher stability than electrochemical samples (eval uated t1/2 = 2800 days at ambient temperature) in relation with a high thermal activation of the conductivity decay (E(a) = 20 kcal/mol). Th e conductivity decay of these films appears to follow a diffusion-cont rolled kinetics. This diffusion phenomenon appears to be solid state d iffusion (D = 10(-18)-10(-17) cm2/s). Polypyrroles doped with 2-naphth alenesulfonate are found to be more stable than samples doped with the usual p-toluenesulfonate.