Polythiophenes with unusual electrical and optical properties based on donor acceptor alternance strategy

The strategy of donor-acceptor alternation was adopted to reduce the energy gap in substituted polythiophenes; energy gaps down to 1.2 eV were obtained, which is a very low value in the class of polythiophenes. Alkoxy groups and dicyanoethenyl groups were used to prepare electron-rich and electron-poor thiophene units. The copolymers were obtained by coupling reaction methods (Suzuki) and by oxidative chemical and electrochemical polymerisation of an opportunely designed substituted terthiophene. X-ray studies and spectroscopic data on the copolymers evidenced that the dicyanoethenyl group as substituent was rather steric demanding and susceptible of side reactions also preventing the n-doping of the material. The conductivity behaviour was unusual but compatible with localised charge carriers.