Solvent effects on the polymerization kinetics of some α-silylated thiophene oligomers. Special influence of the α-silyl group

Oxidation of several silylthiophene oligomers has been studied in aprotic solvents by cyclic voltammetry. Reversible voltammograms were obtained at low or very high scan rates depending on the nature of the oligomer (from 0.05 V s−1 for 5,5‴-bis(trimethylsilyl)quaterthiophene to 25 000 V s−1 for 5-(trimethylsilyl)bithiophene in acetonitrile). The lifetimes of the electrogenerated radical cation were estimated from the appearance of the reversibility of the cyclic voltammogram. The reactivity of silyloligothiophene was found to change to a large extent with the nature of the solvent (two orders of magnitude from dichloromethane to acetonitrile). These results suggest the intervention of the desilylation reaction in the kinetically determining step of the polymerization process.