ATRP in Waterborne Miniemulsion via a Simultaneous Reverse and Normal Initiation Process

Atom transfer radical polymerization with simultaneous reverse and normal initiation process was conducted in a miniemulsion system with the use of highly active transition-metal complexes formed by hydrophobic ligands at concentrations 5−8 times lower than in a typical reverse ATRP process. The molecular weights were essentially determined by the concentration of alkyl halide (used in ∼5-fold excess to a standard radical initiator) and much less affected by the concentration of a standard radical initiator (e.g., AIBN) and/or Cu II complex. Controlled polymerizations of methacrylate, acrylate, and styrene were demonstrated by a linear correlation between molecular weights and monomer conversions and relatively low polydispersities ( M w / M n < 1.3). The resulting latexes showed good colloidal stability with an average particle sized around 250−300 nm. Oil-soluble initiator (e.g., AIBN) provided better control over polymerization than water-soluble initiator (e.g., VA-044). Well-defined waterborne 3-arm star polystyrene and poly( n -butyl acrylate) were synthesized by adding a trifunctional alkyl halide to a reverse ATRP initiating system.