Resolving the incompatibility between SET-LRP and non-disproportionating solvents

Abstract

Cu(0)-catalyzed single-electron transfer-living radical polymerization (SET-LRP) has shown great potential for applications in which well-defined chain end-functionalized polymers are demanded as final products or as intermediates. However, the use of polar reaction media favoring the disproportionation of Cu(I)X species into Cu(0) and Cu(II)X2 was considered a limiting factor specially in the synthesis of complex hydrophobic polymers with functional chain ends. “Self-generated” biphasic systems, in which the polymer phase-separates from the homogeneous reaction mixture above a certain molecular weight, together with fundamental studies on the role of solvent, including catalytic solvent effect, and methodological developments such us the “mixed-ligand” concept served as inspiration, although sometimes in an unknown way, to solve this problem. Today, SET-LRP of both acrylic and methacrylic vinyl monomers is already feasible in both polar and non-polar non-disproportionating solvents using their corresponding bi(multi)phasic “programmed” mixtures with water. Under these conditions, SET-LRP is an interfacial process in which disproportionation and activation events occur independently in the aqueous and organic compartments, and the “self-controlled” reversible deactivation takes place at the interface. Consequently, this design entirely defeats the limiting requirement to exclusively use disproportionating solvents. After a brief discussion of the historical evolution of the field of LRP, starting with the landmark work of Otsu from 1950th, this feature article will describe the elaboration of “programmed” bi(multi)phasic SET-LRP systems starting from initial inspiration to development in laboratory large-scale experiments.

Keywords

• Living radical polymerization
• Single electron transfer
• Mechanisms
• Historical nomenclature
• Systematic nomenclature
• Multiphase system polymerization