CONDUCTING POLYMERS FROM ANODIC COUPLING OF DITHIENYLACETYLENES - ELECTROCHEMISTRY AND POTENTIAL-DRIVEN CONDUCTIVE AND MAGNETIC-PROPERTIES

Anodic coupling of dithienylacetylene and dithienylacetylenes substitu ted with alkyl and all;oxy groups has been investigated in acetonitril e. The resulting polymers have been characterized by cyclic voltammetr y, W-Vis spectroscopy, electrochemical quartz crystal microbalance, in situ ESR and in situ conductivity. The degree of conjugation of the p olymers is increased as the monomer oxidation potential is lowered, wh ich occurs with alkyl-substitution and even more with alkoxy-substitut ion. Alkoxy-substitution in position 3 of the thiophene ring produces the dimer, whereas 4-substitution yields an extensively crosslinked po lymer. A regularly coupled polymer is obtained by 3,4-disubstitution w ith the ethylenedioxy group. The low conductivity (1x10(-3) S cm(-1)) and the high unpaired spin density in the oxidized state of this polym er are explained by localization of charge and spin operated in the di thienyl moieties by the triple bonds. (C) 1998 Elsevier Science S.A. A ll rights reserved.