In order to upgrade the performance of poly(p-phenylenebenzobisoxazole) (PBO) materials and to promote its commercialization

a novel method for preparing PBO resin as developed by the homo- polycondensation of a new AB-PBO monomer

2-(4-methoxycarbonylphenyl)-5-amino-6-hydroxybenzoxazole (MAB)

which was innovatively synthesized by the selective reduction of 4

6-dinitroresorcinol (DNR)

then condensation-cyclization with 4-methoxycarbonylbenzoyl chloride and finaly catalytic-hydrogenation.The results showed that: (1) The intrinsic viscosity of PBO resin prepared from 98.2％ purity MAB was more than 10 dl/g in glassware

the total yield (based on DNR) was more than 64 %

polymerization time was shortened to 15 h and the operation was convenient; (2) MAB was exactly identified by 1H-NMR

13C-NMR

FT-IR and easily prepared at a total yield of 66%.The process has advantages of simple raw materials preparation

controllable selective reduction

one-pot condensation-cyclization

mild hydrogenation condition

and good economics.The selective reduction product: 4-Amino-6-nitroresorcinol hydrochloride (ANR8226;HCl) could be used as a key intermediate in the improvement of PBO performance; (3) The novel synthesis route could be developed into a new technique for commercialization.The new AB-PBO monomer

has outstanding stability (purity decreases only 0.12% after 270 days in the presence of air).There is no need for antioxidant agent in storage and polycondensation.MAB has equi-molar polycondensing group.The novel synthesis route is better than the AA-type 4

6-diamino resorcinol dihydrochloride plus BB-type terephthalic acid monomers co-polycondensation route.