PBO materials possess super mechanical properties and high thermal and chemical resistance due to their special rigid-rod backbones with heterocyclie chemical structure and supermolecular microstrueture. But these structures may be affected by a series of preparing technologies, among which the coagulant is even more important. In this paper the chemical and microstrueture changes of PBO materials coagulated with different solvents were investigated. Analyses of molecular weight and chemical structure of PBO coagulated indicate that the heteroeyclie ring of PBO will experience cleavage in coagulation and in this stage water plays an important role. The final structure of PBO materials may involve several intermediate structures lying between benzoxazole a,d the open ring. Wide-angle X-ray diffraction （WAXD） 20 scans and scanning probe microscope （ SPM ） show that the microstrueture of PBO materials eoagulated in solvents with different properties will change a lot and those coagulants with the smaller rate of diffusion like methanol can cause more ordered molecule alignment containing fewer voids.
