Electron spin resonance study of radiation-induced radicals from maleic anhydride in irradiated frozen solutions

Abstract

Radicals produced from maleic anhydride in 7-irradiated frozen solutions of 2-methyltetrahydrofuran have been identified by their ESR spectra. The initial product is the molecular anion radical I. During thermal annealing at 98 K, radical I converts into the protonated anion II and the X-addition radical IV is formed supposedly from the addition of the solvent radical to the remaining solute molecule. Evidence for X ^H is obtained from the comparison with the spectrum of III produced by loss of an hydrogen atom in polycrystalline samples of succinic anhydride irradiated at room temperature. Radical IV converts into the acyl-type radical V upon uv illumination at 77 K and radical V reverts into IV by thermal annealing at 99-100 K. A similar conversion from III in irradiated succinic anhydride to the acyl-type radical 0=C-CH==CH-COOH and the reverse process have been also found. To interprete the ESR spectra, spectral simulations and the INDO MO calculations have been performed for these radicals. The results are in reasonable agreement with observations.

Novel Synthesis of Macromonomers by Mechanochemical Reaction for the Application to Polymeric Micelles

“…It is difficult to assign the radical structure produced by the mechanochemical reaction of PMMA with MA from these data obtained. Fukaya et al observed the ESR spectra of MA radicals produced by γ-irradiation at 77 K [27], which were not a broad singlet and apparently different from those obtained in this experiment. Tion et al reported that MA radicals produced by mechanochemical reaction of copolymer of MMA and MA (poly(MMA-co-MA)) at -55 ºC disappeared with spectral changes at 0 ºC [28].…”