Radiation‐induced solid‐state polymerization of derivatives of methacrylic acid. III. An electron spin resonance study of radical reactions in irradiated octadecyl methacrylate

Abstract

AbstractThe electron spin resonance spectrum of gamma‐irradiated octadecyl methacrylate (m.p. ≈ 12°C.) was due to a mixture of three radicals formed by (1) loss of a hydrogen atom from the paraffin chain, (2) addition of a hydrogen atom to the double bond, and (3) addition of a monomer molecule to radicals formed by (1) or (2). On warming monomer added to radicals (1) and (2) between −170 and −50°C., and above −50°C. the spectrum was solely due to propagating methacrylate radicals. The total radical concentration decreased slightly at −150°C. and was then constant up to −30°C. A marked decrease in radical concentration occurred from −30 to +12°C., it took place rapidly and reached an equilibrium value after each successive increase in temperature. Differential thermal analysis indicated a solid—solid phase change at −30°C. When the sample was kept at 0°C. there was no further decrease in radical concentration even with 50% conversion to polymer. With 2% added chloranil the (chloranil)− was observed to be of about the same concentration as methacrylate radicals. The initial total radical concentration was lower and decreased to zero by 0°C. on warming. No polymer was obtained.