Yasuro Hori

Nature of peroxy radicals in polypropylene

Abstract Recent ESR studies on structure, motional character and decay reaction of peroxy radicals in irradiated polypropylene, which were made in our group, were summarized. Peroxy radicals must be trapped at the sites with various conformations and mobilities, in principle. However, we took an approximate consideration that the sites can be divided into two kinds, mobile and immobile. This interpretation was very successful in making good simulation procedures of ESR spectra. Internal rotation angles. which represent the orientations of the O-O group around C-O bond with respect to the adjacent C-C bond, both for mobile and immobile radicals were determined. The structure of the site for immobile radicals was found to be corresponding to gauche type and that for mobile one was found to be corresponding to skew type. Motional character of the peroxy radicals was found to be a rotation or rotational vibration around main chain axis. Decay reaction of the mobile peroxy radicals were interpreted by a diffusion controlled mechanism and the interpretation that immobile radicals do not take place in the decay reaction was reflected in the analysis.