Acrylate, methacrylate and styrene monomer radicals produced by the addition of an aminoalkyl radical to the corresponding monomer unit were directly observed by laser flash photolysis. These radicals are characterized by a strong absorption in the near UV/visible part of the spectrum allowing to directly follow their interaction with different nitroxides usable in nitroxide mediated polymerization (NMP). The recombination rate constants were measured: they are in agreement with the literature data when available; other values are new. This procedure is fast and reliable. (c) 2007 Elsevier B.V. All rights reserved.