An electrically-conductive composite prepared by electrochemical polymerization of pyrrole into polyurethane

A study of the electrochemical preparation of conductive composite films from polypyrrole and non-conducting polyurethane resin is presented. Pyrrole and dopants can penetrate through a polyurethane substrate (precoated on a Pt electrode by casting) and electropolymerize on the Pt surface due to the swelling of the coating by the electrolyte solution (dry acetonitrile mixed with ethylene glycol). Cyclic voltammograms show that the diffusion process in polyurethane is inhibited for larger anions. The electrical conductivity of the composites falls in the range 1–35 S/cm and is influenced by the electropolymerization conditions (electrode potential, reaction time, type of supporting electrolyte, etc.). The mechanical properties of the composites resemble those of pure polyurethane. Scanning electron micrographs, FT infrared spectra and other experiments indicate that polypyrrole is dispersed in the polyurethane matrix like a net with unusually thickset ‘knots’.