Long-Range Polar Effect on the C-ON Bond Homolysis in (tert-Butyl[1-(diethylphosphonyl)-2,2-dimethylpropyl]aminoxyl) SG1-Based Alkoxyamines

Abstract

Alkoxyamines and persistent nitroxyl radicals are important regulators of nitroxide-mediated radical polymerization. Because the polymerization times decrease with the increasing rate constant of the homolysis of the C-ON bond between the polymer chain and the nitroxyl moiety, the factors influencing the cleavage rate constant are of considerable interest. Because alkyl acrylate monomers are among the most used in polymerization, we present the measures of the rate constants ( k _d) of the C-ON bond cleavage for new SG1 based alkoxyamine models containing para-substituted aromatic acrylates (4-XC ₆H ₄OC(O)C(Me)H-SG1). It appears that the values of k _d increase with the electron-withdrawing properties of the para-substituent groups (4-X) of the ester SG1-based alkoxyamines.