2,5‐Dihydro‐1<i>H</i>‐imidazole‐Based Nitroxides as Prospective Mediators in Living Radical Polymerization

Abstract

Abstract A number of spectroscopic methods were applied to obtain kinetic parameters of reactions modelling the 2,5‐dihydro‐1 H ‐imidazole 1‐oxide mediated living polymerization of acrylates. The homolysis rate constants of alkoxyamines based on five nitroxides were measured by EPR spectroscopy at different temperatures. The recombination rate constants k c between the corresponding alkyl radicals and the nitroxides were measured by means of laser flash photolysis. The time‐resolved chemically induced dynamic nuclear polarization (TR‐CIDNP) experiments revealed the negligible contribution of disproportionation in the recombination reaction. In addition, the thermodecomposition of alkoxyamines in the NMR probe showed the absence of intramolecular elimination of hydroxylamines from the corresponding alkoxyamines. Analysis of the kinetic parameters showed that the 2,5‐dihydro‐1 H ‐imidazole 1‐oxide type radicals are promising mediators for the living polymerization of acrylates and methacrylates.