SYNTHESIS AND ELECTROCHEMICAL PROPERTIES OF LIQUID-CRYSTALLINE POLYTHIOPHENES

In this work, we synthesized thiophene monomers containing a mesogenic group at 3-position of the thiophene ring. Homopolymers were obtained by the dehalogenation polycondensation, with zero valence nickel as a catalyst. And copolymers were synthesized by the Stille coupling reac tion with zero valence palladium as a catalyst. Their phase transition behaviors and electrochemical properties were examined by polarized o ptical microscopy, differential scanning calorimetry and cyclic voltam metry. Homopolymers and copolymers involved a cyano group at the end o f mesogen exhibited a nematic phase, while a smectic phase was shown f or the homopolymer having the ester bond between the thiophene ring an d alkyl spacer. The pi-pi absorption peaks of copolymers were shifted to longer wavelengths than that of homopolymers having same mesogenic group. After annealing of the polymer, the oxidation-reduction potent ial peaks of the polymer were lower than that of the neat samples. The conductivity values of I-2 doped thermal treated homopolymers and cop olymers were 10(-2) S/cm and 10(-1) S/cm, respectively.