Ellipsometric study of acrylonitrile electropolymerization on nickel

Abstract We have studied the initial stages of acrylonitrile electropolymerization on nickel, by in-situ ellipsometry with phase and azimuth modulation, in a specially designed spectroelectrochemical cell. The optical measurements led to the following specific results: (1) The grafting of the monomer can start only on a site where the native oxide is being reduced. (2) Up to the first monolayer the process depends on the electric current, while the three-dimensional growth is controlled only by the electric field. Empirical laws of growth are proposed. (3) In the monolayer range the complex dielectric constant ( ϵ ) of the film is mainly dependent on the perturbations induced in the superficial properties of the nickel electrode. Beyond the first monolayer the film exhibits two structures (homogeneous and inhomogeneous) whose ratio depends on the preparation conditions. (4) The films are conducting and show an important optical anisotropy. The real part of ϵ is always negative suggesting that the conduction is essentially controlled by free electrons.