Molecular organisation of electrochemically prepared conducting polypyrrole films

Molecular structure-preparation condition relationships are reported for electrochemically prepared polypyrrole-toluene sulphonate electrically conducting films. Polypyrrole films have been prepared from aqueous solutions employing a range of anodic potentials (0.5-1.6 V versus SCE)and at several temperatures. Consistently films grown using higher potentials and at lower temperatures exhibited greater electrical conductivities. The molecular organisation in these series of films was evaluated using quantitative X-ray scattering procedures. The X-ray scattering data show that polypyrrole molecules adopt a planar-type conformation in which the planes of the pyrrole moieties have a preferred orientation with respect to the electrode surface. This anisotropy is enhanced in samples prepared at low temperatures or at high anodic potentials, and such anisotropic films have greater electrical conductivity. Structural mechanisms for these observations are discussed.