MOLECULAR-ORIENTATION AND CONDUCTIVITY IN HIGHLY ORIENTED POLY(P-PHENYLENE VINYLENE)

Highly oriented films of poly(p-phenylene vinylene) (PPV) were prepared by uniaxial stretching during thermal conversion of a water-soluble sulfonium polyelectrolyte precursor polymer. The precursor films were stretched up to seven times their original length. Doping of the stretched PPV films was achieved by dipping into a 0.12 M solution of FeCl3 in nitromethane. The d.c. electrical conductivity of these doped films was measured as a function of the doping time and as a function of the temperature between 80 and 300 K. Compared with the maximum conductivity obtained in unstretched PPV films doped with FeCl3 (sigma(dc) = 35 OMEGA-1 cm-1), the stretched films showed a higher conductivity (sigma(dc) = 230 OMEGA-1 cm-1) when measured along the stretching orientation. The molecular structure and the changes caused by doping of stretched PPV films were studied by infra-red dichroism, transmission electron microscopy and electron diffraction.