Reversible-Deactivation Radical Polymerization of Vinyl Monomers Mediated by Schiff Bases

N,N '-Bis(salicylidene)-1,2-phenylenediamine (salophen), a versatile ligand for organometallics, was found to be capable of mediating the reversible-deactivation radical polymerization (RDRP) of vinyl acetate (VAc) and N-vinylpyrrolidone (NVP) with predictable molecular weights and the formation of block copolymers. The mechanism was first studied via the substituent effect with different salophen derivatives and then rationalized by density functional theory (DFT) calculations associated with the control studies and chain-end characterization. We discovered that the radicals react with the imine carbon of salophen to generate an active species that further deactivates the propagating radicals to form the dormant species. The observed living characteristics were attributed to the equilibrium between the dormant species and the active species with radicals.