Design and use ofβ-phosphorus nitroxides and alkoxyamines in controlled/“living” free radical polymerizations

Persistent nitroxides and their corresponding alkoxyamines are important regulators of living radical polymerization. Here we describe the synthesis of β-phosphorus nitroxides bearing a β-hydrogen, that present very interesting properties for the control of the radical polymerization of styrenes, acrylates and other monomers. A large series of alkoxyamines derived from these nitroxides was prepared, and Electron Spin Resonance (ESR) was used to determine both the temperature (Tc) and the rate constant (kd) for their homolysis. For the whole series of alkoxyamines (27 compounds), a very good linear correlation was found between Tc and logkd. Satisfactory linear correlations were found between Tc and calculated (PM3 method) Bond Dissociation Energy (BDE) of the NO-C bond, for series of alkoxyamines with the same type of leaving radical. The characteristics of free radical polymerization of styrene carried out in the presence of these new nitroxides and alkoxyamines will be discussed.