A perspective on redox-switchable ring-opening polymerization

A polymer's properties and functionality are directly related to the constituent monomers from which it was synthesized, the order in which these monomers are assembled, and the degree to which monomers are enchained. Furthermore, a standing challenge in the field of polymer synthesis is to provide temporal polymerization control that can be leveraged to access a variety of advanced polymer architectures. Though many polymer classes are attractive for various applications, polyesters have drawn considerable recent interest due to the potential of these materials to provide biodegradable alternatives to other, often petroleum derived, polymeric materials that create concerning, long-term environmental impacts. Many of these biodegradable polyesters can be produced via the transition-metal catalyzed ring-opening polymerization of cyclic ester and cyclic ether monomers. Through researchers' quest to access precise and well-defined polyesters via ring-opening polymerization, an intriguing class of stimuli-responsive catalysts have emerged. More specifically, catalyst systems have been developed in which their electronic nature may be modulated via either ligand-based or active metal site-based redox-switchability. These redox-switchable catalysts have been shown to exhibit altered chemoselectivity and kinetic modulation as a function of catalyst redox-state. Herein, we will discuss the beginnings, select recent advancements, and an outlook on the field of redox-switchable ring-opening polymerizations.