Regioregular Head-to-tail (HT)-type polythiophene was synthesized by deprotonative nickel-catalyzed cross-coupling polymerization of 2-chlorothiophene bearing neopentyl benzenesulfonate group at the 3-position. The obtained HT-regioregular polymer was found dissolved in chloroform or THF, while it turned to water soluble upon heating the polymer 2 at 185 °C for 10 min by the liberation of the protected neopentyl group. The thin-film of the polymer showed remarkable improvement of the conductivity ca. 10 3 times before/after heating suggesting thermally-induced intramolecular doping polythiophene by the formed sulfonic acid at the side chain. The related doping was also observed in a poly(phenylacetylene) derivative, which was synthesized by rhodium-catalyzed polymerization. Copolymerization of such thiophene and acetylene bearing neopentyl sulfonate with 3-alkylthiophene and phenylacetylene produced the corresponding statistical copolymers, respectively, demonstrating the formal self-doping of poly(3-alkylthiophene) and poly(phenylacetylene).

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Thiophene-thiophene copolymers composed of 3-alkylthiophene and a small amount of thiophene bearing cyclic siloxane are synthesized by random copolymerizatin of 2-chloro-3-dodecylthiophene and 2-chlorothiophene bearing cyclic tetrasiloxane as a substituent. Deprotonative metalation of chlorothiophenes with a bulky magnesium amide followed by the addition of nickel catalyst undergoes polymerization to afford statistical copolymer based on the feed ratio. The copolymer bearing a small amount of (1-10%) cyclic siloxane is subjected to the formation of thin film. The treatment of the obtained thin film with an acid vapor results in the formation of the film insoluble in any of solvent through the formal networking of poly(3-dodecylthiophene) by the effect of a small amount of cyclic siloxane moiety. The measurement of electric properties reveals to exhibit improved conductivities to 10 6 times higher before and after the acid treatment.

Regioregular polythiophene bearing a benzenesulfonate group, which involved an alkylene spacer between thiophene and benzene ring, was synthesized.The obtained polythiophene was shown to improve its conductivity by heating the polymer thin film through the transformation of the ester group into the corresponding sulfonic acid.

Differently substituted thiophene–thiophene-alternating copolymers were formally synthesized employing a halo-bithiophene as a monomer. Nickel-catalyzed polymerization of bithiophene with substituents at the 3-position, including alkyl-, fluoroalkyl-, or oligosiloxane-containing groups, afforded the corresponding copolymers in good to excellent yield. The solubility test in organic solvents was performed to reveal that several copolymers showed a superior solubility. X-ray diffraction analysis of the thin film of the alternating copolymers composed of methyl and branched oligosiloxane substituents was also performed, and the results suggested the formation of a dual-layered film structure.