Study On The Preparation And Polymerization Of Model Compounds PBO

Poly(p-phenylenebenzobisoxazole)(PBO) fiber, called as the21th "supper fiber", has attracted much attention for its high strength, modulus and thermal stability performances, and has been widely application in the high-tech fileds. Nearly all the PBO fibers used in China are imported. However the foreign countries blockade the technology and the price is very high. Therefore it is of great significance to carry out studies on synthesis, structure and properties of PBO for fiber materials. For polymerization of PBO is uncontrollable, low and widely distribution of molecular weight, model compounds were designed and synthesized in this paper and used as monomer to prepare high molecular weight PBO polymer. Furthermore the polymerization process of PBO using this technique is explored in this paperBecause the purity is low,4,6-diaminoresorcinol dihydrochloride (DAR) was purified with hydrochloric acid solution. The best process of recrystallization was determined by exploring the impact of concentration of hydrochloric acid solution, the ratio of hydrochloric acid and monomer and the times of recrystallization. The recrystallized DAR was characterized by FT-IR,1HNMR, MS, etc. The purity can up to99.6%after recrystallization.According to the molecule structure of PBO, two kinds of model compounds were prepared with terephthalic acid (TPA) and4,6-diaminoresorcinol (DAR) by molecular design. The purity and yield of model compounds was explored by changing the temperature and the concentration of monomer. Moreover, the preparation process of the trimer model compounds was optimized. The model compounds were characterized by FT-IR,13CNMR, MS, Raman, etc. The results showed that the structure of synthesized model compounds was consistent with the pre-designed structure.Because the DAR was easily oxidized and TPA was poorly solubility in the PBO polymerization process, this paper synthesized four kinds of PBO polymer by changing the monomers. The two polycondensation monomers are DAR and TPA, DAR and trimer model compounds with TPA terminated, TPA and trimer model compounds with DAR terminated, trimer model compounds with TPA terminated and trimer model compounds with DAR terminated, respectively. The performance of polymer was compared by TG and the molecular weight. The result showed that the PBO polymer’s thermal decomposition temperature reached520℃and the molecular weight was22915g/mol which was synthesized by two model compounds monomer. The reason is that the model compounds monomer has better solubility and oxidation resistance compare with DAR and TPA, which certify the precise ratio of two groups in the polycondensation. The method can be used to instead of the polymerization route of removalled HC1.