The near‐infrared spectra of polymers

A series of step reaction polymers have been prepared and studied as melt films or in solution in the overtone region and the combination region of the near‐IR. Systems containing aryl rings show bands in the 2.13‐ to 2.16‐μm region which are not observed in those systems not having aryl rings. Polyester, polyamide, and urea‐formaldehyde polymers show carbonyl, hydroxyl, and NH overtones. Polyurethanes show only the intense band of NH, in the 2.0‐ to 2.1‐μm region. Ureaformaldehyde and polyamides show this same band. Relative band intensities were compared to the first overtone of CH which appears at 1.67–1.72 μm. In this way, polymers can be compared in a quantitative manner, both with respect to reaction conditions and effect of heat curing.