β,β-Disubstituted oligothiophenes, a new oligomeric approach towards the synthesis of conducting polymers

Abstract

Abstract The electropolymerization of methylthio-substituted oligothiophenes 2 – 4 has been studied. Theoretical and experimental results reveal that only 4,4′-disubstituted derivatives yield polymeric films. The reason for this is that electron-donating methylthio (=methylsulphonyl) substituents in the ‘outer’ β -positions of the starting compounds 2 – 4 , which cause high spin densities at the corresponding α -C atoms, favour fast coupling steps between the reacting oligomers during all stages of the electropolymerization. All data clearly indicate that the electropolymerization of donor-substituted thiophenes is not a chain propagation process but a series of successive ‘dimerization’ steps. The resulting polymers have been characterized by voltammetric measurements, in situ conductivity experiments and spectroelectrochemistry.