Mechanistic aspect of reverse atom transfer radical polymerization of n-butyl methacrylate in aqueous dispersed system

Reverse atom transfer radical polymerization (ATRP) of n-butyl methacrylate was conducted in an aqueous dispersed system. Using a water-soluble initia tor (V-50), a nonionic surfactant (Brij 98), and a hydrophobic ligand (dNbp y) to complex a copper halide, polymers with relatively well controlled mol ar masses and low polydispersities wen: obtained. Stable latexes with parti cle diameters within 150-300 nm were formed. Kinetic studies were performed under various experimental conditions. The influence of the concentrations of the catalyst, the surfactant, and the initiator as well as the temperat ure on the polymerization rate, molecular weight, and particle size was inv estigated. Because of the lack of high molecular weight polymer during the early polymerization stage, reverse ATRP in the aqueous dispersed system pr esumably has a different "nucleation" mechanism from that of a conventional emulsion polymerization. In addition, fast decomposition of the initiator prevents the continuous entry of radicals into the particles from the aqueo us phase. As a result, the kinetics of the reverse ATRP is fundamentally di fferent from a classical emulsion polymerization and is controlled mainly b y the atom transfer equilibrium.