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Spectral profiling of radicals in polymer degradation based on electron spin resonance imaging (ESRI)

2001; Elsevier BV; Volume: 73; Issue: 3 Linguagem: Inglês

10.1016/s0141-3910(01)00133-1

1873-2321

Shulamith Schlick, Krzysztof Kruczała, M. V. Motyakin, J.L. Gerlock,

Electron and X-Ray Spectroscopy Techniques

We have developed 1D and 2D electron spin resonance imaging (ESRI) in order to deduce the spatial variation of radical properties in polymers exposed to UV radiation in the presence of oxygen, or thermally treated. The accelerated degradation of poly (acrylonitrile-butadiene-styrene) (ABS) containing Tinuvin 770 as the hindered amine stabilizer (HAS) was studied in a weathering chamber equipped with a Xe source that mimics the spectral range of sunlight. The HAS-derived nitroxides detected by ESR occupy two sites and were assigned to radicals located in domains differing in their monomer composition. The spatial distribution of the radical intensity obtained by 1D ESRI indicated that nitroxide radicals are produced initially only on the irradiated side, but the intensity of radicals on the opposite side increases with irradiation time. By contrast, the spatial distribution of nitroxides produced during thermal degradation at 600C is spatially homogeneous. Via 2D ESRI it was possible to visualize the spatial variation of the ESR spectra and to deduce the relative intensity of the nitroxides in the two distinct sites along the selected spatial coordinate. The spectral profiling made possible by ESRI provided spatial details that can be used to deduce morphology-sensitive chemical processes along the sample depth.