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 (kd) of the C-ON bond cleavage for new SG1 based alkoxyamine models containing para-substituted aromatic acrylates (4-XC6H4OC(O)C(Me)H-SG1). It appears that the values of kd increase with the electron-withdrawing properties of the para-substituent groups (4-X) of the ester SG1-based alkoxyamines.
烷氧胺和持久的亚硝基自由基是亚硝基介导的自由基聚合的重要调节剂。由于聚合时间随着聚合物链和亚硝基部分之间的C-ON键的断裂速率常数的增加而减少,因此影响断裂速率常数的因素具有相当大的兴趣。由于烷基丙烯酸酯单体是聚合中最常用的单体之一,我们提出了基于新的SG1烷氧胺模型的包含对位取代芳香丙烯酸酯(4-XC6H4OC(O)C(Me)H-SG1)的C-ON键断裂速率常数(kd)的测量值。看来,对SG1基烷氧胺的酯类的4-X对位取代基团的电子吸引性质(4-X)的kd值随之增加。