Novel organosynthetic routes to polythiophene and its derivatives

Polythiophene and its 3-alkyl derivatives have been synthesized by novel organosynthetic techniques. The organochemical syntheses were carried out by dehydrohalogenation of 2-halogenothiophene (or its 3-alkyl derivatives) or by dehydrogenation of thiophene (or its 3-alkyl derivatives). Copolymers can also be obtained from a solution involving two (or more) kinds of thiophene monomer species. The resulting polythiophene and its derivatives have well-defined chemical and electronic structure and molecular weights as large as 2.5 × 105. The poly(3-alkylthiophenes) with long alkyl side groups, typically poly(3-hexylthiophene), are readily soluble in common organic solvents and can subsequently be processed into uniform films from their solution. These solution-cast films, furthermore, can be easily stretched up to a stretching ratio of about five. The stretched films exhibit excellent conductivity (as high as 200 S/cm) after doping. The effect of the copolymerization between two thiophene monomers is also discussed.