Electrochemically-mediated ATRP

Matyjaszewski and coworkers developed a process [255] for an electrochemically mediated ATRP. They use applied voltage to drive the production of Cu -i- ions that catalyze the polymer formation. Because the rate of the reaction is controlled by a redox equilibrium between cuprous and cupric ions, electrochemistry permits the regulation of the concentration of each species. 

Such lithographic procedure allows for the precise control of the initiator grafting density at the micrometer scale and allows, in principle, the patterning of surfaces with domains presenting controlled polymer brush grafting densities and therefore controlled thicknesses. It is in principle transposable to recently reported ways to electrochemically mediate ATRP... 

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... 

The proposed mechanism of ATRP mediated through electrochemical control over the ratio of CuVCu" and (re)gene-ration of activators is shown in Scheme 6. 

---