ENDOR SPECTROSCOPIC STUDY OF MACRORADICALS IN IRRADIATED ORIENTED NYLON-6

Macroradicals formed by hydrogen atom elimination in uniaxially and bi axially oriented nylon-6 have been investigated at low temperature usi ng a Q-band ENDOR technique. Hyperfine coupling constants were obtaine d from the observed IH ENDOR spectra for the protons located at alpha- , beta-, and gamma-positions relative to the unpaired electron in the radical -CO-NH-CH-CH2-CH2-. Principal values for alpha-proton anisotro pic coupling tensor have been determined. A degree of angular disorien tation of the radical centers -CH- along the axes of biaxially oriente d polymer was evaluated. The protons of the beta-methylene group were found to be magnetically nonequivalent and therefore the plane of the free carbon was twisted. The deviation from the ideally planar transco nfiguration corresponds to the rotation around the C(alpha)-C(beta) bo nd on average angle 11-degrees. A change in beta-proton ENDOR spectrum has been revealed under mechanical loading of oriented specimens. The results obtained evidenced for the appearance of reversible torsional deformation in stressed macroradicals.