New conducting pyrrole-thiophene co-polymer from an oligomer precursor: Electrochemical characterisation

A new oligomer of N,N'-bis(2-pyrrolyl methylene)-3,4-dicyano-2,5- diaminothiophene possessing cyano-substituted thiophene and pyrrole residues linked together by azomethine groups was used for the electrochemical polymerisation of conducting films. The approach used for the oligomer design favours inter-chain interactions through hydrogen bonding and negative charge stability through the cyano substitute thiophene. The oligomer was successfully electropolymerised at 0.67 V vs Ag ⁺/Ag from 0.1M tetrabutylammonium tetrafluoroborate (TBABF ₄)/acetonitrile as a dark blue film on the surface of platinum electrodes. Cyclic voltammetry has been used to investigate the redox behaviour of the films. The electrically conducting polymer showed p-doping/neutralisation behaviour. The effect of different electrolytes such as TBABF ₄, tetrabutylammonium perchlorate (TBAClO ₄), lithium perchlorate (LiClO ₄) and sodium perchlorate (NaClO ₄) on the redox switching and the stability of the polymer films was investigated. Infrared and UV-vis spectra of oligomer and polymers are presented. The evolution of the film growing process is shown by UV-vis spectroscopy.