Electrochemical synthesis of polythiophenes and polyselenophenes

Thiophene and selenophene, when substituted in the 3-position by an electron-donor group such as methyl or methoxy, lead to the formation of a polymeric film when electrochemically oxidized. Thus, poly(3-methylthiophene) (PMeT), poly)3-methoxythiophene) (PMeOT), poly(3-methylselenophene) (PMeS) and poly(3-methoxyselenophene) (PMeOS) have been synthesized either by electrolysis at fixed potential or by repetitive cyclic voltammetry. These polymers are electrical conductors and can be cycled between the oxidized state (doped) and the neutral state (undoped). This charge-discharge process is accompagnied by reversible changes in colour, which can be seen by u.v.-visible spectroscopy.