Atom transfer radical polymerization in miniemulsion: Partitioning effects of copper(I) and copper(II) on polymerization rate, livingness, and molecular weight distribution

The effects of partitioning of Cu(I) and Cu(II) species to the aqueous medium on the polymerization rate (R-p), molecular weight and molecular weight distribution in the miniemulsion atom transfer radical polymerization system of styrene/CuBr/4,4'-dinonyl-2,2'-bipyridyl at 90 degrees C were investigated. According to both simulation (invoking the partitioning data for n-butyl methacrylate (Macromolecules 2000, 33, 7310-7320)) and experiment showed that the R-p and polydipersity (M-w/M-n) were higher in miniemulsion than in the corresponding solution polymerization as a result of a decrease in deactivator concentration (Cu(II) species) in the organic phase. Simulations indicated quantitatively that the increase in M-w/M-n was caused by (i) a decrease of activation-deactivation cycles and (ii) an increase of bimolecular termination.