Alternating donor-acceptor substitutions in conjugated polythiophenes

A series of bithiophenes, disubstituted with electron donor and electron acceptor groups, have been synthesized. The electronic effects exerted by these groups, on the electrochemical oxidation potential of bithiophenes, are additive, which allows us to control the overall substituent effect and make it compatible with the electropolymerization of these molecules. The electrochemical characterization of the resulting polymers has revealed unusual properties, in the case of unsymmetrical disubstitution with strong electron acceptor and donor groups. Charge confinement is observed for the first oxidated state of poly(3-cyano-3'-methoxybithiophene), which has been interpreted by the existence of multiple potential wells, created by these push-pull substituents alternating along the conjuated polythiophene chain.