Conducting polymers as coatings: Electrochemical and density functional theory investigations of the polymerisation

Electroactive materials such as polypyrrole and polythiophene have many applications including their use as coatings in the metal finishing industry. Electrochemical and density functional theory (DFT) studies of a series of derivatised thiophene molecules have revealed that the production of electroactive polymeric films can be related to the coupling pathways of the radical cations generated during anodic oxidation of the monomer Electro-oxidation of (E)-styrylheterocycles shows complex electrochemical behaviour with alkene oxidation preceeding that of the aromatic/heterocyclic rings to produce redox inactive insulating films. A nitrile substitutent was introduced at the alkene spacer linkage in an attempt to alter the electron density distribution in the radical cation and thus minimise the likelihood of adverse couplings via this site. This strategy proved successful with redox-active polymers formed on oxidation of (Z)-α,β-diarylacrylonitriles. These results were supported by the use of DFT which confirmed that the π-spin density at the alkene spacer linkage was significantly reduced in the presence of the nitrile substituent allowing α,α'-coupling reactions to predominate