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Effect of [Pyridylmethanimine]/[CuI] Ratio, Ligand, Solvent and Temperature on the Activation Rate Constants in Atom Transfer Radical Polymerization

Authors

  • Wei Tang,

    1. Center for Macromolecular Engineering, Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA
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  • Ajaya Kumar Nanda,

    1. Center for Macromolecular Engineering, Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA
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  • Krzysztof Matyjaszewski

    Corresponding author
    1. Center for Macromolecular Engineering, Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA
    • Center for Macromolecular Engineering, Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA. Fax: +1 412 268 6897
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Abstract

Summary: The effect of [L]/[CuI] ratio, ligand, the choice of solvent and temperature on the activation rate constants in ATRP with catalyst complexes formed with two pyridylmethanimine ligands [PMI, i.e., N-propyl-pyridylmethanimine (NPPMI) and N-octyl-pyridylmethanimine (NOPMI)] were studied. Maximal values for the apparent rate constants were observed at an [L]/[CuI] ratio of ∼2/1 and 1/1 in polar and nonpolar solvents, respectively. This is similar to the results obtained with the CuI/bpy system and was attributed to the formation of [CuI/L2]+Br and [CuI/L2]+CuIBrmath image species. The CuI/NPPMI system was only soluble in polar reaction media; however, the CuI/NOPMI complex was soluble in both polar and less polar reaction media. The activation rate constants increased with increasing temperature and the value of activation energy (Ea) for CuI/NPPMI in the activation process was 58.1 kJ · M−1 · K−1.

original image

Arrhenius plot of ln ka versus 1/T for the activation process for NPPMI and bpy in acetonitrile; [CuIBr/NPPMI2]0 ([CuIBr/bpy2]0)/[EtBriB]0/[TEMPO]0/[TCB]0 = 20/1/10/2 × 10−3M.

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