Electron nuclear double resonance spectra and stereoconfiguration of macroradicals in irradiated isotactic polypropylene

Electron nuclear double resonance spectra of the macroradicals -CH2-C (CH3)-CH2- produced by irradiation in oriented samples of isotactic PP were recorded and analyzed. The HFC constants were measured for the alpha -methyl and beta -methylene protons of the radical and estimated for remote protons. The conformational structure of the macroradicals was established. The abstraction of hydrogen atoms from isotactic PP macromolecules leads to an increase in the internal rotation angles about C-alpha-C-beta bonds in the trans- and gauche-segments of the radical, as well to tilting and out-of-plane bending of the radical center C-beta C-alpha(C-Me)C-beta. By the electron nuclear double resonance technique, the formation of radicals upon irradiation is detected not only in crystalline but also in irregular regions of PP.