ENDOR spectroscopic study of macroradicals in irradiated oriented Nylon-6

Abstract Macroradicals formed by hydrogen atom elimination in uniaxially and biaxially oriented nylon-6 have been investigated at low temperature using a Q-band ENDOR technique. Hyperfine coupling constants were obtained from the observed 1H ENDOR spectra for the protons located at α-, β-, and γ-positions relative to the unpaired electron in the radical -CO-NH-CH-CH2-CH2-. Principal values for α-proton anisotropic coupling tensor have been determined. A degree of angular disorientation of the radical centers -CH- along the axes of biaxially oriented polymer was evaluated. The protons of the β-methylene group were found to be magnetically nonequivalent and therefore the plane of the free carbon was twisted. The deviation from the ideally planar transconfiguration corresponds to the rotation around the Cα-Cβ bond on average angle 11°. A change in β-proton ENDOR spectrum has been revealed under mechanical loading of oriented specimens. The results obtained evidenced for be appearance of reversible torsional ...