Ligand effect and oxygen tolerance studies in photochemically induced copper mediated reversible deactivation radical polymerization of methyl methacrylate in dimethyl sulfoxide

Abstract

Well-defined poly(methyl methacrylate) was prepared by a photochemically induced reversible deactivation radical polymerization using 50–200 ppm of a copper catalyst in dimethyl sulfoxide under both an inert atmosphere and in the presence of a limited amount of air. The effect of the ligand structure and concentration on the kinetics and polymerization control was investigated. Under an inert atmosphere, equimolar amounts of the ligand, such as tris(2-pyridylmethyl)amine (TPMA) or N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA), were sufficient to achieve well-controlled polymerization of MMA. In the presence of air, a well-controlled polymerization started just after some induction time, which was dependent on the concentration of the TPMA ligand. Irradiation at λ > 350 nm provided both a photochemical reduction of an initially-added copper(II) catalyst, which complexed with either PMDETA or TPMA ligand, to a copper(I) activator, and a photochemical regeneration of the copper(I) activator after its oxidation by oxygen. Successful chain-extension polymerization performed without degassing of the polymerization mixture confirmed the high degree of livingness of the photopolymerization system even in the presence of a limited amount of air.