Electropoly merization: direct film formation on metal substrates II locus of polymerization

Abstract

Films of polyacrylonitrile and polymethacrylonitrile can be produced in situ on metal electrodes by the electrolysis of a conducting solution of the monomer. Electroanalytical techniques have been used to investigate the locus of the polymerization and also to attempt to determine the rate constants for propagation and termination. Differential capacitance measurements indicate that there may be some adsorption of these monomers at potentials where they are electroactive when NaN03 is used as electrolyte but no adsorption of the polymer produced was detected. When the electrolyte contains quaternary alkyl ammonium ions, they are preferentially adsorbed. Sweep voltammetry indicates that direct reduction of both monomers occurs by a two electron transfer step which precedes a fast follow-up reaction which may be either addition of a second monomer molecule or protonation. Because of practical difficulties imposed by the system, the use of rotating disc electrode was limited but, when used in conjunction with a digital simulation technique, it allowed calculation of kp and k, for the anionic polymerization based on the electrolysis of acrylonitrile containing tetraethylammonium p-toluene sulphonate.