Electrogeneration of poly-1,3-dimethoxybenzene uniform coatings by consecutive square-wave potentials: Kinetic studies

Abstract

When consecutive square-wave potentials are applied to a platinum electrode in 1,3-dimethoxybenzene + tetrabutylammonium perchlorate + acetonitrile solutions, a polymer film is generated on the metal. If the anodic polarization time for each wave is greater than 1 s a bilayer morphology is obtained: an inner uniform adherent shiny film, and an outer powdery non adherent film. For anodic polarization times shorter than 1 s only the uniform adherent film grows at upper potentials in the range 1300–1900 mV. More positive potentials can produce pinholes in the film. The lower potential of each wave promotes a recovery of the initial conditions around the electrode; it has no influence on the kinetic growth of the film, only on the morphology, down to −1000 mV (electrolyte discharge). Measurements of the weight of electrogenerated polymer (by ultramicrogravimetry) and the electric charge consumed in generating polymer films for different treatment times and for different monomer and electrolyte concentrations, allowed the empirical kinetics to be established: R p = k[monomer] 0.8[TBAP] 0.7 The activation energy is 16 kJ mol −1. Differences from literature values of the empirical kinetics, obtained from constant potential polarization, suggest that a complex mechanism exists.