Alkyl chloride initiators for SET-LRP of methyl acrylate

Single-electron transfer living radical polymerization (SET-LRP) proceeds by an outer-sphere single-electron transfer mechanism that induces a heterolytic bond cleavage of the initiating and propagating R-X (where X = Cl, Br, and I) species. Therefore, unlike the homolytic bond cleavage mechanism claimed for ATRP, SET-LRP is expected to show a small dependence of the nature of the halide group on the apparent rate constant of activation. This means the R-X with X = Cl, Br, and I must all be efficient initiators for SET-LRP and no chain transfer must be observed in the case of initiators with X = Br and I. Here, we report the SET-LRP of methyl acrylate initiated with the alkyl chlorides methyl-2-chloropropionate (MCP) and chloroform (CHCl3) and catalyzed by Cu(0)/Me-6-TREN/CuCl2 in DMSO at 25 degrees C. A combination of kinetic and structural analysis was used to elucidate the MCP and CHCl3 initiating behavior under SET-LRP conditions, and to demonstrate the very small dependence of the SET-LRP apparent rate constant of propagation on X while providing polymers with well defined architecture. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4917-4926, 2008.