Synthesis of Bulky Nitroxides, Characterization, and Their Application in Controlled Radical Polymerization

This paper describes the synthesis of several highly sterical hindered alkoxyamines based on 6-membered cyclic nitroxides and their application as initiators/regulators in the controlled nitroxide-mediated radical polymerization of n-butyl acrylate and styrene. Rate constant k(d) and activation energy E-a of the C-O bond of the novel alkoxyamines are reported. Conformational studies on the new nitroxides are performed by X-ray analysis and by DFT calculations. The polymerization of n-butyl acrylate can be conducted at 60 degrees C showing that these hindered nitroxides are highly valuable to conduct nitroxide-mediated acrylate polymerization (NMP). In addition, low temperature (SO degrees C) styrene polymerizations are disclosed.