Indolinic nitroxides: evaluation of their potential as universal control agents for nitroxide mediated polymerization

Indolinic nitroxides derived from 2,2-diphenyl-3-phenylimino-2,3-dihydroindol-1-yloxyl (DPAIO) nitroxide were designed to improve the bulk polymerization of methacrylate derivatives. The corresponding alkoxyamines were prepared by reacting alkyl halide and nitroxide in the presence of tin hydride and PbO2. The replacement of one phenyl ring at the C-2 position on the nitroxide by either a neopentyl or an isopropyl group led to compounds with faster decomposition kinetics and better selectivity for the C–ON bond homolysis. The alkoxyamines derived from these two nitroxides were used to control the polymerization of methyl methacrylate and were also tested for the polymerization of styrene as a model for mono-substituted monomers. The shift of the molar mass distribution during the NMP of styrene showed for the first time that pure homopolymerization of styrene and methacrylate derivatives could be controlled by the same nitroxide, thus opening the way to a universal nitroxide for NMP.