The synthetic methods of Poly(p-phenylene benzobisoxazole) (PBO) were elaborated through the polycondensation in PPA

trimethylsilanization

mesophase polymerization

and the method of TA salt in this paper. And a novel method was also introduced for preparing PBO as developed by the homopolycondensation of a new ABPBO 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- methoxycarbonylbenzoylchloride and finally catalytic hydrogenation.Finally the synthetic methods of other homogeneous poly(benzobisoxazole)s were reviewed by exemplifying the type of chain alkene

the polycyclic type

the type of bephenyl

the heterocyclic type demonstrated.