This article follows a previous study (Macromolecules 2005, 38, 5485) demonstrating that the nitroxide SG1-mediated polymerization of methyl methacrylate can be achieved at 90 °C with high conversion and high quality of control by introducing a small amount of styrene. In this work, the resulting polymer was characterized and the presence of SG1-based alkoxyamine at the polymer chain-end was identified, supporting the livingness of the macromolecules. In particular, it was shown that the alkoxyamine end group was connected to a single styrene terminal unit and that the methyl methacrylate penultimate unit had a strong effect on the temperature of dissociation. Consequently, the copolymerization of methyl methacrylate with a low molar proportion of styrene could be performed at temperatures below 90 °C. The polymer was also used as an efficient macroinitiator in the polymerization of styrene and n-butyl acrylate, to form methyl methacrylate-based block copolymers.