E.S.R. Spectra of Free Radicals Relevant to Methacrylate Polymerization

Abstract

Carbon-based free radicals were generated by thermal cleavage of the tetraester

Me₂C(COOME)-CH₂-CMe( COOMe )- CMe ( COOMe )-CH₂-C( COOMe )Me₂

which is a model for head-to-head units in a poly(methyl methacrylate ) chain. The resulting electron spin resonance spectrum had higher resolution than the 'nine-line' spectrum previously reported; this enabled identification of the component radicals. In the present case, the spectrum was well matched by a summation of spectra of the

Me₂C(COOME)-CH₂-CMe( COOMe )

radical and the 1-methoxycarbonyl-1-methylethyl radical

Me2-C-COOMe

derived from it by loss of methyl methacrylate. Both of these radicals were generated in separate experiments. Radicals were also generated from starting materials containing a CD₃ group in place of the single CH₃.