Electron spin resonance study of γ‐irradiated poly(acrylic acid)

Abstract

AbstractElectron spin resonance (ESR) spectra of poly(acrylic acid) (PAA) γ‐irradiated in air at room temperature and recorded at room temperature and at liquid‐nitrogen temperature have been studied to identify the radiation products. The ESR spectra are composed of eight lines with hyperfine splittings of 23 ± 1 G and 11 ± 1 G. The method of least‐squares total curve fitting, employing the Lorentzian line shape function, to the observed spectra enabled the assignment of the spectra. Computed spectra obtained by the superposition of a singlet and the spectra due to chain radicals are considered to give the best fits to the observed ESR spectra. The singlet is assigned to the radicals COOH, and the component 10‐line spectra are assigned to the chain radicals CH3CHCH2 ∼ and/or ∼ CH2CHCH2 ∼. The observed change in line shape with temperature of the ESR spectra is attributed to the hindered oscillations of the methyl groups about the CαCβ bond axis of the chain radicals. The existence of the methyl groups is confirmed by the measurement of infrared absorption.