Citation

Peiyi Wu, and Heinz W. Siesler. Two-Dimensional Correlation Analysis of Variable-Temperature Fourier-Transform near-Infrared Spectra of an Amorphous Polyamide. AIP Conference Proceedings 2000, 503, 18-30.

Abstract

Near-infrared (NIR) spectra of a totally amorphous polyamide measured over the temperature range from 25 °C-200 °C were 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 v(CH)v(CH)overtones (5400-6100 cm−1). Among them, two bands at 5810 cm−1 (aliphatic CH) and 6010 cm−1 (aromatic CH) were found to be very sensitive to the temperature-induced structural changes of the polyamide under examination. In the v(NH)v(NH) overtone region (6300–6800 cm−1), the asynchronicity of the bands assigned to the vibrations of the free and hydrogen-bonded NH groups indicates 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 the 2D correlation spectra, a splitting of the first v(NH)v(NH) overtone of free NH groups into two components at 6780 cm−1 (totally free) and 6740 cm−1 (free-end) can be observed.