Resonance Raman spectroscopic investigation of the mechanism and kinetics of the degradation of N,N-hexamethylene bishexamide, a Nylon 6,6 model compound

We report a mechanistic study of the photo-oxidative degradation of N,N-hex amethylene bishexamide, a Nylon 6,6 model compound. Resonant Raman intensit ies of the amide and its previously identified enal degradation product art : recorded as a function of the duration of the irradiation of the amide wi th 266 nm laser pulses. The time dependences of the Raman intensities an co nsistent with those predicted by a kinetic mechanism for photo-oxidation. I n particular, the rate of formation of the enal, probed by monitoring the R aman intensity of its C=O stretch peak at 1680 cm(-1), agrees well with the rate of cleavage of the C-N bond in the amide, revealed by the time depend ence of the intensity of the Am II (C-N stretch) vibration at 1537 cm(-1). Rate constants for important steps in the degradation mechanism are obtaine d from the analysis. (C) 2001 Elsevier Science Ltd. All rights reserved.