Conductivity and Anisotropy of Electrochemically Prepared Conducting Polypyrrole Films

Abstract

Thick, freestanding, flexible films of polypyrrole have been prepared from pyrrole monomer in propylene carbonate solvent containing tetra ethyl ammonium p‐toluene sulfonate electrolyte. Films were electrodeposited onto titanium substrates at temperatures from −40° to 25°C, and were found not only to have high conductivity, but were also anisotropic. The electrodeposition temperature, electrode dimensions, current density, voltage, and solvent were found to affect the properties of the polymer. The values of conductivity of the polypyrrole films increased with decreasing electrodeposition temperature and increasing current density. For a substrate, the highest conductivity value, 514 S/cm, was obtained with samples prepared at a temperature of −20°C and a current density of 3.0 mA/cm2. The ratio of conductivities measured along and across the surface of the samples increased with decreasing electrodeposition temperature and current density, but was strongly dependent on the electrode geometry. A conductivity of 996 S/cm and a ratio of 3.3 was obtained for a film deposited on a long narrow substrate, compared with a ratio of 1.2 for a square substrate. Films produced in propylene carbonate solvent possessed better properties than when either acetonitrile or mixtures of propylene carbonate and acetonitrile were employed as solvents.