The changes of chemical structure along a polymer chain during thermal and chemical treatment were examined by FT-lR spenxoscopy. The thermal cyclization of poly(2,5-diaminobenzamide-terephthalamide) (PDBTA) and poly(4,4'-dia- vino-6-carbamoylbenzanilide-terephthalamide) (polyul-DACB -TPC)) in the absence and in the presence of catalyst such as LiCl produces both a large amount of quinazolone and a small a mount of benzoxazinone along a polymer chain; the amount of quinazolone and benzoxazinone formed by dehydration and deamination reaction through condensation reaction of pendant carbamoyl fyoup and amide bond along a polymer chain during thermal treatment of the polymer was determined using calibration curve obtained with the absorbance of model compounds of 6-benzoylamino-2-pheny1-4-(3H) -quinazolone and of 6-benzoylamino-2-phenyl-4H-3,1-benzoxazin-Lone measured at wavenumber of 1358 and 1742cm -1 It turns out that thermal cyclopolycondensation of PDBTA without LiCl at 270'I produces 76% of quinazolone and 24% of benzoxazione as well as with LiCl gives 89% and 11%, respectively. The chemin cyclization of PDBTA and poly(p-DACB-TPC) in fuming H2SO4, on the contrary, produces nitril groups exclusively along a polymer chain via strong dehydration reaction of carbamoyl groups along polymer chain in fuming H2SO4 ; it is confirmed by chemical treatment in fuming H2SO4 of model compound Rr, leis(2,5-N-benzoyldiamino) benzamide, which gives around 80% of bis(2,5-N-benzoyldiamino) benzonitrile, VII.
