Electrochemical and optical properties of thiophene-alkylheteroaromatic copolymers

α-Terthienyl and 2,5-di(2-thienyl)pyrrole, n-alkylated at the β-position of the central ring, have been oxidized electrochemically or chemically to afford electroactive polymers which were characterized by cyclic voltammetry, spectroelectrochemistry and FTi.r. These systems, which can be viewed as α-linked alternating copolymers of bithiophene with a 3-alkylthiophene or 3-alkylpyrrole, display superior effective degrees of conjugation compared with homopolymers of similarly substituted 3-alkylheteroaromatics. Chemically generated materials are soluble in a variety of organic solvents, but fail to produce coherent films when cast from these due to lower degrees of polymerization than similarly produced 3-alkylthiophene homopolymers. Electrogenerated polymers are insoluble despite apparently comparable degrees of polymerization as determined by FTi.r. end-group analysis. Oxidation potentials of the monomers are reduced in proportion to the number of alkyl substituents.