A study of internal rotation in polymers by the analysis of the asymmetry in the EPR spectra

Summary

In our opinion the work reported above clearly demonstrates how an examination of the anisotropy in the EPR lines obtained from oriented an isotropic polymers can yield a lot of valuable data on the structure and internal rotation in polymers, particularly information about changes taking place during polymorphic phase transitions. For example, the fact that changes observed in the shapes of spectra obtained from polycrystalline teflon are quite different from those obtained in teflon films (the experimental data relate to the crystalline phase exclusively [15]) indicate that the crystal structures of the two materials must somehow differ. This argument is further supported by the fact that the recombination rates of radicals are different in the two materials [16]. A more rigorous analysis of the asymmetry in the singlet line would obviously provide certain quantitative data as to how complete is the alignment of the polymeric chains and what kind of angular distribution persists. We did detect a relationship between the shapes of the EPR spectrum and the amount by which the film is stretched (thickness) but have not done any systematic work on this problem.