An electrochemical quartz crystal microbalance-based investigation of the properties displayed by electroactive polypyridine films

The properties of poly-2,5-pyridine films, deposited on gold electrodes through a nickel-catalyzed cathodic polymerization route carried out in acetonitrile, were re-investigated by electrochemical quartz crystal microgravimetry in conjunction with cyclic voltammetry and coulometry. Special attention was paid to the ion transport during film reduction and ion binding of the polymer characterized by both electroactive and coordinative properties. The suitability of the electrochemical quartz crystal microbalance for the study of chemically modified electrode surfaces results in reliable information pointing out that polymeric chains in the framework are characterized by the presence of bipyridyl moieties grafted upon one another by coordinating nickel(II) ions whose coordination shell was identified. Moreover, the nickel-doped polymer turned out to undergo two cathodic processes both leading to the polymer changing from the insulating to the conductive state. The former is due to the reduction of coordinated nickel ions and is accompanied by the release of the counter anions originally present, while the uptake of cations from the supporting electrolyte is accompanied with reduction by the injection of electrons into the polymer backbone. The program developed for the simultaneous acquisition of experimental data and their processing is described.