Electron spin resonance studies on oriented polyoxymethylene

Electron spin resonance spectra of stretched polyoxymethylene irradiated with γ‐rays from a Co60 source were studied. With suitable treatment three kinds of spectra were selectively observed: doublet with irradiation and measurement at room temperature; singlet with irradiation and measurement at about −180°C.; triplet with the irradiation at about −180°C. and the measurement at −102°C. The doublet and the triplet spectra showed anisotropy, while the singlet did not. These observations confirm the assignment of the spectra so far reported with unoriented polyoxymethylene, i.e., CH2O, OĊHO, OĊH2 for the singlet, doublet, and triplet, respectively. The doublet spectrum is treated as related to the anisotropic hyperfine coupling tensor, the anisotropic g value and the chain conformation in crystalline polyoxymethylene. A rather small value, p≈0.45, was obtained for the spin density at the central carbon atom.