Covalent Binding of Redox Active Centres to Preformed Regioregular Polythiophenes

The synthesis of regioregular head-to-tail poly[3-(6-bromohexyl)thiophene] is reported, together with its reaction with 2-carboxyanthraquinone (Anth) to give an example of a regioregular polythiophene containing pendant functional groups (87% loading). NMR data on the two soluble polymers are reported together with preliminary studies of some of their physical properties. Cyclic voltammetric studies of anthraquinone polymer coated electrodes show that the observed response is coverage dependent: thin films display four redox couples due to the Anth(0/-/2-) processes and the p-and n-doping of the conjugated thiophene backbone. Thick films are rectifying in the sense that reduction of the Anth groups is inhibited on the negative sweep. Spectroelectrochemical studies confirm the nature of the anodic p-doping process (the film turns red to nearly colourless) and show characteristic changes on reduction (red to black).