CONFORMATIONAL EFFECTS ON ELECTRICAL AND SPECTROSCOPIC PROPERTIES OF 1,2-DI(2-THIENYL)ETHYLENES AND CORRESPONDING POLY[(2,2'-DITHIENYL)-5,5'-DIYLVINYLENES]

1,2-Dialkyl-substituted 1,2-di(2-thienyl)ethylenes have been synthesiz ed and investigated by cyclic voltammetry. The bulk of the alkyl subst ituents was modulated in order to progressively increase the torsional angle between the thiophene rings and the plane of the olefinic bond, from a fully planar structure to highly twisted systems. Distortion m arkedly affects the UV spectra and the oxidation peak potentials of th e monomers. The electrochemical polymerization experiments gave the fo llowing results: i) (E)- and (Z)-dithienylethylene systems produced po lymers with identical properties; ii) progressive deviation from plana rity increased the oxidation peak potential of the monomer, as far as the polymerization was inhibited; iii) long and rigid monomeric units reduced chain flexibility, leading to materials with low conductivity and unsatisfactory mechanical properties.