Infrared analysis of depth profiles in UV-photochemical degradation of polymers

Photochemical degradation of commercially available polymers after ultra-violet irradiation was investigated using the infrared ATR method with the view of observing chemical structural changes. Depth profiles of the chemical structural changes were obtained by simulating the angle resolved ATR spectra phenomenologically. The profile in the depth direction of the degradation of polymer matrix and additives was observed in some polymers. The photo-degradation appearing from the surface to the depth in μm order in the samples was demonstrated in this study. The profile of the degradation shows an extreme degraded layer in the sub-μm depth near the surface and a gradually decreased layer in the inner part of the polymers as in the scope of our study. Many polymers were thought to have an accumulated layer of the degraded species after photo-irradiation near the surface. Drastic photo-degradation was not observed in PMMA by infrared spectroscopy. This polymer has a very low value of extinction coefficient in the ultra-violet region. The depth region of the extreme degradation near the surface and the wavelength in the ultra-violet light absorbed in polymer is almost of the same order. This evidence supported the result many researchers predicted but we confirmed it using our depth profile technique.