Reverse Atom Transfer Radical Polymerization in Miniemulsion

Abstract

Reverse atom transfer radical polymerization was successfully carried out in a miniemulsion system at 70 °C with a doubled solid content (≥20%) and 1/6 amount of nonionic surfactant, Brij 98 (2.3 wt % based on monomer, or 0.58 wt % based on the aqueous phase), compared to the previously reported system. Hexasubstituted TREN/CuBr2 and 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044) were employed as a highly active radical deactivator and a water-soluble initiator, respectively. Controlled polymerizations were demonstrated by attaining linear correlations between molecular weights and monomer conversion, and relatively narrow molecular weight distributions (<1.5). The resulting latexes showed good colloidal stability with an average particle size around 200−250 nm. Monomer droplet nucleation was proved to be the predominant nucleation mechanism in the system. The polymerization kinetics was governed mainly by the atom transfer equilibrium. Other parameters, such as ligand, surfactant, initiator, temperature, and deactivator (CuII) were investigated from both the polymerization kinetics and the colloidal stability points of view. The livingness and the end-functionality of the resulting polymers were demonstrated by the further chain extension study.