Formation of regioregular head-to-tail poly[3-(4-butylphenyl)thiophene] byan oxidative coupling polymerization with vanadium acetylacetonate

The mechanism for the formation of head-to-tail (R-T) poly[3-(4-butylphenyl )thiophene] by oxidative coupling polymerization with a catalytic amount of vanadium acetylacetonate was investigated. Polymerization was carried out in the presence of vanadium acetylacetonate, trifluoromethane sulfonic acid , and trifluoroacetic anhydride under an oxygen atmosphere in 1,2-dichloroe thane at room temperature. Polymers and oligomers obtained after several po lymerization times were characterized by gel permeation chromatography, IR, and NMR spectroscopies. With these findings and the reactivity of monomer and dimers based on ab initio density functional theory, the polymerization was found to proceed mainly through the formation of H-T linkages due to t he high spin density at the 2-position of 3-(4-butylphenyl)thiophene and th e calculated total energy of dimers. (C) 2001 John Wiley & Sons, Inc.