EPR study of the photoinitiated polymerization of methyl methacrylate

Abstract

By means of previously described continuous-flow procedures, we have studied by electron paramagnetic resonance spectroscopy the photolysis of 4,4′-azo-bis-(4-cyanopentanoic acid), R′N: NR′, in solution at 25° and 40°, the two solvents used being toluene and methyl methacrylate, MMA, each containing 8 v/v% N,N-dimethylformamide, DMF. With the use of the first solvent mixture, only the EPR signal of the R ·′radical, CH 3Ċ(CN)CH 2CH 2COOH, was observed; with the use of the second, the absorption was consistent with the presence of two species: a minor component, R ·′, and a major component, addition radicals of structure ▪ with n ⩾ 0. These results are analogous to those previously reported for similar studies of the photolysis of 2,2′-azo-bis-(2-methylpropionitrile), RN: NR in toluene and in M MA. In particular, at a given temperature, the spectroscopic properties of the addition-radical component observed in each study were the same in every significant detail. In a like fashion, the photolysis of RN: NR in toluene and MMA, both neat and containing 8 v/v% DMF, has been investigated at 25° and 40°. The results were essentially the same as those found for the previously reported RN: NR investigations employing neat toluene and MMA, so demonstrating the presence of the DMF to cause no appreciable effect on the spectroscopic properties of the R · radical, CH 3Ċ(CN)CH 3, or the addition radical ▪.