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Depth Profiling of Photooxidized Styrene-Isoprene Copolymers by Photoacoustic and Micro-Fourier Transform Infrared Spectroscopy

Volume 53, Number 2 (Feb. 1999) Page 157-163

Gonon, Laurent; Vasseur, Olivier J.; Gardette, Jean-Luc

Transmission micro-FT-IR (Fourier transform infrared) and photoacoustic (PAS) FT-IR analysis have been combined to determine the oxidation profiles of various photooxidized polyisoprene-polystyrene copolymers. It is shown that only the polyisoprene phase is oxidized. The front photooxidized layers (0-22 mu m) are analyzed by PAS, while the bulk (11-150 mu m) is characterized by cross-sectional analysis of microtomed layers. A good agreement between the two methods is found in the region where the analyzed layers overlap (11-22 mu m). The extent of the oxidation was determined by monitoring the ratio between the intensity of the carbonyl absorbance at 1718 cm-1 and the absorbance at 1600 cm-1. The results given in this article show that PAS FT-IR can be a rapid and nondestructive technique of quantitative characterization of the surface degradation of aged polymers.