Direct measurements of the addition and recombination of acrylate radicals: Access to propagation and termination rate constants?

Acrylate radicals produced by the addition of an aminoalkyl radical to five acrylate monomers were directly observed by transient absorption spectroscopy, which allowed us to easily follow their chemical reactivity. It was possible (1) to characterize their absorption in the visible part of the spectrum, (2) to calculate their absorption properties, (3) to determine the energy barriers of the addition through quantum mechanical calculations, (4) to monitor the kinetics of the subsequent addition to another monomer unit, and (5) to follow the recombination of two acrylate radicals. These two latter points could mimic the propagation and termination reactions of polymerization‐propagating acrylate radicals. Methacrylate and acrylonitrile radicals were also studied. The obtained results were in good agreement with the propagation rate constants determined by the well‐established pulsed laser polymerization techniques. Our method could likely provide rapid access to both the propagation and termination rate constants in suitable systems and appears to be powerful and promising for studying and comparing the reactivities of different acrylate monomer structures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3577–3587, 2006