ELECTROGRAFTING OF ACRYLIC AND METHACRYLIC MONOMERS ONTO METALS - INFLUENCE OF THE RELATIVE POLARITY AND DONOR-ACCEPTOR PROPERTIES OF THE MONOMER AND THE SOLVENT

The possibility of grafting a series of alkyl polyacrylates and polyme thacrylates onto a nickel cathode by electropolymerization of the pare nt monomers has been investigated and has emphasized the critical impo rtance of the solvent used. Indeed, the intensity of the inhibition pe ak, which is the electrochemical mark of the cathode passivation as re sult of the polymer grafting, clearly depends on both the polarity and the donor-acceptor properties of the solvent. The Gutmann concept is used to account for these experimental results. An increase in the don icity of the solvent used for the electrochemical medium has allowed, for the very first time, several polyacrylates and polymethacrylates [ such as poly(ethyl acrylate), poly(methyl methacrylate), and poly(2-tr imethylsilyloxyethyl methacrylate)] to be electrografted onto Ni. This observation is consistent with a competition process between the mono mer and the solvent for being adsorbed on the cathode and amassing in its very close vicinity. The outcome of this competition is controlled by the relative polarity (in case of low donicity) and the relative d onor-acceptor properties (when the difference is high enough) of the m onomer/solvent pair, and by the monomer concentration tin case of weak competition). A semiquantitative relationship has also been observed between the monomer ability to be electrografted and the electron-acce pting character of the vinyl beta-carbon atom as measured by C-13 NMR.