Stereoregulation in Living Radical Polymerization

This perspective article reviews the recent developments in stereoregulation in living radical polymerization of various polar vinyl monomers including methacrylates, acrylamides, vinyl esters, and vinyl amides. The stereoregulation should rely on an added Lewis acid, a polar solvent, or a multiple hydrogen-bonding additive, which can interact with the polar groups around the growing polymer terminal and/or of the monomer to induce the stereospecific chain growth, while the living or controlled chain growth is governed by a metal catalyst or a reversible chain transfer agent. The stereospecific living radical polymerization is thus achievable by the judicious combination of the stereocontrollable additive or solvent and the living radical polymerization catalyst or mediator. This methodology is relatively easily applied to the precise synthesis of stereoblock or stereogradient polymers, in which the stereochemistry of the enchainment is abruptly or gradually changed, respectively. This review also discusses other possible approaches to the simultaneous control using chiral metal catalysts or mediators for living radical polymerization or by utilizing a physically confined nanospace for the controlled and stereospecific chain growth.