The hydrogen bond in thermal strengthening of aramid systems containing polyamide-benzimidazole fragments

An IR-spectroscopic study was conducted in aramid systems containing benzamide and benzimidazole fragments which allowed evaluating the character and magnitude of the enthalpy of formation of intermolecular hydrogen bonds under the effect of high temperatures. Strengthening of the H bond in benzimidazole groups and weakening of the bond in benzamide (benzimidole) groups were demonstrated. The possible co-existence of imidole-quinoid groups with benzamide and imidazole fragments was established. Polarization studies of the oriented state demonstrated high anisotropy of absorption for most vibrations in the 400–4500 cm^-1 region.