SPECTROSCOPIC STUDIES OF THE INTERFACE BUILT-UP DURING THE FORMATION OF AN ELECTROPOLYMERIZED POLYACRYLONITRILE THIN-FILM ON A COPPER SURFACE CATHODE

We present in this work a series of results obtained on the atmospherically oxidized copper-acrylonitrile system, our aim being to follow the deposition, by grafting and growing, of electropolymerized polyacrylonitrile film. Combining analytical means of electrochemistry-XPS, UPS and infrared reflection adsorption spectroscopy (IRAS)-allows quite an accurate description of this phenomena. The film was deposited by the imposition of a linearly growing negative tension to the copper electrode dipped in an electrolytic solution containing acrylonitrile. The polarization is stopped at different potentials of the current-potential characteristic. These potentials correspond to the formation steps of the interface. Thus we describe, successively, the nature of the initial states (atmospherically oxidized copper) and the final states (insulating and covered polyacrylonitrile thin film of 20-30 A) in relation to the change in density of occupied electronic superficial states. The appearance of this insulating and covering film is expressed on the current-potential characteristic by an inhibition peak, named the passivation peak. Moreover, the non-stoichiometric character of the superficial copper oxide is identified and permits the use of a low electrochemical potential (before the oxide electroreduction potential) to graft the polymer onto non-oxidized sites.