Electron paramagnetic resonance study of the photoinitiated polymerization of methacrylonitrile
Using previously detailed continuous-flow techniques, we have studied by electron paramagnetic resonance, EPR, the photolysis of 2,2′-azobis(2-methylpropionitrile), RN:NR, in solution at ca. 25°. The solvents used were toluene, methacrylonitrile, and toluene-methacrylonitrile mixtures. With toluene as the solvent, we observed only the EPR signal from the R· radical. As the toluene was replaced by an increasing proportion of methacrylonitrile keeping the other reaction conditions constant, the signal from R· fell in intensity and was progressively replaced by one other absorption, this being consistent with addition radicals of structure R-[-CH2-C(CN)CH3-]n-CH 2-Ċ(CN)CH3 with n ≥ 0. Spin and relative concentration measurements of R· and the addition radical component as a function of reaction conditions were made and used in a kinetic analysis of this reaction system.
