Electroinitiation direct

Alternating equimolar copolymers of vinyl acetate and ethylene and alternating copolymers of vinyl acetate and acrylonitrile have been reported (127,128). Vinyl acetate and certain copolymers can be produced directly as films on certain metallic substrates by electroinitiation processes in which the substrate functions as one electrode (129). 

Electroinitiated polymerization proceeds by direct electron addition to monomer to generate the monomer anion-radical, although initiation in some systems may involve the formation of an anionic species by electrolytic reaction of some component of the reaction system (often the electrolyte) [Olaj, 1987]. 

However, there was no confirmation of the view that initiation is due to direct electron transfer, since most of the work on electroinitiated anionic polymerization was carried out with sodium nitrate whose cation had a less positive value of half-wave potential than the monomers used. Exceptionally, polymers were produced by the electrolysis of acrylonitrile solutions in dimethyl formamide and dimethoxysulfoxide in the absence of a salt. 

Generally, it is difficult to prove direct electroinitiation experimentally due to the instability and low concentration of the radical ions formed from the monomer. When the medium between the electrodes contains only the monomer which undergoes polymerization at high field intensities, direct electroinitiation is clearly involved [310]... 

Indirect electroinitiation occurs by electrolysis of the supporting electrolyte in the presence of monomer when conditions for direct initiation are not fulfilled. Cerrai et al. [311] electrolyzed R4N + P and R4N + I3 in 1,2-dich-loroethane in the presence of isobutyl vinyl ether. They found iodine formed by the oxidation of anions... 

In 1970, Funt and Blain published a thorough study of the electroinitiated polymerisation of styrene in the presence of tetrabutylammonium perchlorate. The kinetics of these reactions were followed in methylene chloride with a cell provided with a sintered-glass membrane and a sampling device at the anode compartment. S-shaped time-conversion curves were obtained indicating the accumulation of chain carriers during the electrolysis. The results were treated assuming that the concentration of active species was directly proportional to the time-integrated current flow, and that no termination oc-... 

Electroinitiation— which is not to be confiised with initiation by an electron beam— is done by direct electrolysis of the reaction mixture. The reaction mixtiu-e usually contains an organic solvent, the monomer, and an inorganic compoimd that allows to conduct the current or participates in the ionization process itself (76). The polymerization proceeds via either free radicals or ions, depending on the reaction conditions and the substances present in the reaction mixtiu e. 

Whenever vinyl monomers are electropolymerized, two situations must be distinguished depending on whether the vinyl monomer is the precursor of the initiating species or not. Either the polymerization is directly initiated by the activated monomer or the initiation is indirect whenever the active species (radical, anion, or cation) is generated by a compound other than the monomer (conducting salt, solvent, or properly selected additives). Besides these electroinitiated polymerization processes, a very recent report also demonstrated that electrochemistry is a valuable tool to mediate atom transfer radical polymerization (ATRP). Indeed, an externally applied electrochemical potential can activate the copper catalyst by a one-electron reduction of an irutially added air-stable cupric species (Cu /ligand) allowing... 

Direct deposition of the protecting film by electroinitiating polymerization in the electrolyte bath is an alternative to the electrodeposition of preformed polymers. Compared to cata-phoresis, this strategy does not need high electrical potentials, whereas the film adhesion maybe improved to some extent. Early contributions to this technique of deposition of in situ electro-polymerized acrylic and vinyl monomers in organic and aqueous media have been already reviewed elsewhere by Mengoli et... 

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