Novel synthesis

characteristics and application of new AB-PBO monomer 4-(5-amino-6-hydroxybenzoxazole-2-yl) benzoic acid salt（ABAS）were studied The results showed that ABAS was onepot synthesized from methyl 4-(5-nitro-6-hydroxybenzoxazole-2-yl)benzoate (MNB) with a yield of 84% and purity of 99% via alkali hydrolysis and reduction

which had the advantages of simple procedure

low pollution and cost savingThe mechanisms of alkali hydrogenation and acidification with 4-(5-nitro-6-ydroxy benzoxazole-2-yl)benzoic acid dipotassium salt as intermediate were proposedWith MNB below 95% purity

the ABAS approaching 99% purity could also be prepared by the twostep method of hydrolysis and reductionThe ABAS was identified with 1 H NMR

13C NMR

FT-IRIts initial decomposition temperature was measured to be 290℃

and it had excellent thermostability

oxidation resistance and outstanding storage stabilityUsing ABAS of 99% purity

PBO resin was easily prepared by self-polycondensation for 13 h at 230℃ as endpolymerization temperature in glassware and its intrinsic viscosity was more than 15 dl·g-1. The procedure had the characteristics of equimolar polycondensing group

safe operation

easy industrialization and etc.