[en] The C-phenyl-N-tert-butylnitrone/azobisisobutyronitrile pair is able to impart control to the radical polymerization of n-butyl acrylate as long as a two-step process is implemented, that is, the prereaction of the nitrone and the initiator in toluene at 85 degrees C for 4 h followed by the addition and polymerization of n-butyl acrylate at 110 degrees C. The structure of the in situ formed nitroxide has been established from kinetic and electron spin resonance data. The key parameters (the dissociation rate constant, combination rate constant, and equilibrium constant) that govern the process have been evaluated. The equilibrium constant between the dormant and active species is close to 1.6 x 10(-12) mol L-1 at 110 degrees C. The dissociation rate constant and the activation energy for the C-ON bond homolysis are 1.9 x 10(-3) s(-1) and 122 +/- 15 kJ mol(-1), respectively. The rate constant of recombination between the propagating adical and the nitroxide is as high as 1.2 x 10(9) L mol(-1) s(-1). Finally, well-defined poly(n-butyl acrylate)-b-polystyrene block copolymers have been successfully prepared.
Center for Education and Research on Macromolecules (CERM)
Politique Scientifique Fédérale (Belgique) = Belgian Federal Science Policy ; Fonds de la Recherche Scientifique (Communauté française de Belgique) - F.R.S.-FNRS ; Centre National pour la Recherche Scientifique, France ; Communauté Wallonie-Bruxelles: Commissariat Général aux Relations Internationales ; Fonds pour la formation à la Recherche dans l'Industrie et dans l'Agriculture (Communauté française de Belgique) - FRIA