Electropolymerization : direct film formation on metal substrates-I: Kinetics and mechanism

Attempts have been made to produce, in situ, polymer films on tinplate cathodes by the electrolysis of conducting solutions of vinyl monomers for use in the can-lacquering industry. Study of a range of vinyl monomers revealed that film formation occurs at low monomer conversion only in the electrolysis of acrylonitrile and methacrylonitrile in NN'-dimethyl formamide. The highest rates of film formation were obtained by constant current electrolysis when tetraethyl ammonium p-toluene sulphonate (McKee Salt) was used as electrolyte. The rate of film formation increases with monomer concentration to a maximum and then falls rapidly. Chain propagation occurs by an anionic mechanism with ion pair formation favoured at high monomer concentrations. The physical properties of the coloured films produced rarely approach those required industrially and the method does not represent an alternative approach to the lacquering of food and beverage cans.