ESR spectroscopy and other methods

Many comprehensive treatises on electron spin resonance have been published in recent years [37—46] and some reviews deal specifically with the ESR spectra of irradiated or mechanically degraded polymers [47—53]. The main feature of hyperfine splitting and their relation to the conformation of macroradicals will only be outlined. More developed treatments can be found in Refs. [37—53]. Specific cases will be discussed under the heading of each polymer. 

The most important characteristic of ESR spectra is their hyperfine structure. The number, position and width of the lines in the spectra depend on the nature and on the conformation of the radical. The hyperfine structure of the spectra results from interaction of the unpaired electron with neighbouring atoms possessing resultant nuclear spin. When these are only hydrogen atoms 

Hyperfine interaction with a protons includes isotropic and anisotropic coupling. The latter depends on the orientation of the Ca-H bond in the 

Hyperfine interaction with j3-protons is mainly isotropic. The isotropic coupling constant takes the form 

Chemical evidence for trapped free radicals has been obtained by the observation of various reactions initiated by these radicals after irradiation. These are those of grafting, oxidation, isotope exchange and post-irradiation crosslinking. 

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