ELECTRICAL-CONDUCTIVITY OF IODINE-DOPED POLY(PARA-PHENYLENE VINYLENE) MODEL COMPOUNDS BLENDED WITH POLYSTYRENE

We synthesized 15 trimeric poly(para-phenylene vinylene) (PPV) model compounds containing various substituents in the phenyl rings and characterized the structure by H-1 and C-13 NMR. The trans,trans-isomers are almost planar, while those containing methoxy groups in the central ring exhibit the ortho-methoxy-anti conformation. For cis,cis-isomers a non-planar form is proposed in which the three phenyl rings are perpendicular to the plane of the olefinic links. The solubilities were found to increase by (i) CH3 and OCH3 groups in the central ring, (ii) heavy OCH3 substitution in the terminal rings and (iii) cis-configurations of the ethylenic bonds. The more soluble compounds (> 2 g/100 ml CHCl3) were blended with polystyrene and iodine to give black electrically conducting films. Their conductivity (0.1-1 OMEGA-1 cm-1), which varies with the ratio polystyrene:model compound:iodine, is very stable at room temperature.