Chemical and electrochemical polymerization of 3-alkylthiophenes on self-assembled monolayers of oligothiophene-substituted alkylsilanes

Monolayers of oligothiophene-substituted alkylsilanes, chlorodimethyl(11-(3-(2,2'bithienyl))undecyl)-silane and chlorodimethyl(11-(3'-(2,2':5',2 "-terthienyl))undecyl)silane, are subject to electrochemical oxidation within the monolayer to afford more highly conjugated oligomers with lower redox potentials. The electrochemical polymerization of 3-methylthiophene is promoted by monolayers of the oligothiophene-substituted silanes on the electrode surface to form smooth, highly adherent films of poly(3-methylthiophene). The effect of monolayers of an electroactive monomer on the rate of deposition of poly(3-methylthiophene) is compared to the effect of low concentrations of oligomers in solution. Chemical polymerization of 3-octylthiophene on substrates modified with the redox-active silanes gives films of poly(3-octylthiophene) which display reversible solvatochromism without dissolving the polymer. These thin films are sensitive to low concentrations of chloroform in the vapor phase or in aqueous solution.