Gamma-ray-induced modifications of the chemical structure of an ion exchange resin

Gamma-ray irradiation of ion exchange resins used for processing nuclear effluent may lead to considerable modifications of the molecular structure and macroscopic properties. In the present study, crosslinked poly(4-vinylpyridine) (P4VP), irradiated by a 137Cs γ-source up to an integrated dose of 14400 kGy, has been investigated. The particle-induced desorption-mass spectrometry (PDMS) technique is able to detect the radiation-induced structural degradation of such an infusible and insoluble material. From the results of PDMS, a coherent description of the production of specific radical fragments and modified chains is proposed. Both the nature of these fragments as well as their formation, as a function of the dose of irradiation, correlate with results of electron paramagnetic resonance spectrometry and Fourier transform infrared spectroscopy, and with thermogravimetric and dynamical mechanical analysis. In addition, analysis of the soluble and insoluble fractions helps to discriminate between different possible processes. In particular, it is shown that the loss of pyridine fragments correlates well with chemical measurements like the loss of protonatable sites