Two-dimensional near-infrared correlation temperature studies of an amorphous polyamide

Near-infrared spectra of a totally amorphous polyamide measured over the temperature range 25-200 degreesC was analyzed using generalized two-dimensional (2D) correlation spectroscopy. At least, five distinct bands at 5690, 5810, 5900, 5980 and 6010 cm(-1) were identified in the region of the CH overtones (5200-6200 cm(-1)). Among them, two bands at 5810 (aliphatic) and 6010 cm(-1) (aromatic) are found to be very sensitive to the temperature-induced structural changes of the polyamide under examination. In the nu (NH) overtone region (6300-6800 cm(-1)), the asynchronicity of the bands assigned to the vibrations of the free and hydrogen-bonded NH groups indicate a complicated dissociation mechanism and the existence of different hydrogen-bonded species in the investigated totally amorphous polyamide sample. Owing to the spectral resolution enhancement in 2D correlation spectra, a splitting of the first overtone of the free NH stretching vibration into two components at 6780 (totally free) and 6740 cm(-1) (free-end) can be observed. (C) 2001 Elsevier Science Ltd. All rights reserved.