ELECTROGENERATION OF POLY-1,3-DIMETHOXYBENZENE UNIFORM COATINGS BY CONSECUTIVE SQUARE-WAVE POTENTIALS - KINETIC-STUDIES

When consecutive square-wave potentials are applied to a platinum elec trode in 1,3-dimethoxybenzene + tetrabutylammonium perchlorate + aceto nitrile solutions, a Polymer film is generated on the metal. If the an odic polarization time for each wave is greater than 1 s a bilayer mor phology is obtained: an inner uniform adherent shiny film, and an oute r powdery non adherent film. For anodic polarization times shorter tha n 1 s only the uniform adherent film grows at upper potentials in the range 1300-1900 mV. More positive potentials can produce pinholes in t he film. The lower potential of each wave promotes a recovery of the i nitial conditions around the electrode; it has no influence on the kin etic growth of the film, only on the morphology, down to - 1000 mV (el ectrolyte discharge). Measurements of the weight of electrogenerated p olymer (by ultramicrogravimetry) and the electric charge consumed in g enerating polymer films for different treatment times and for differen t monomer and electrolyte concentrations, allowed the empirical kineti cs to be established: R(p) = k[monomer]0.8[TBAP]0.7 The activation ene rgy is 16 kJ mol-1. Differences from literature values of the empirica l kinetics, obtained from constant potential polarization, suggest tha t a complex mechanism exists.