Synthesis Of MWNTs/PBO Fibers And Investigation Of PBO Polymerization Mechanism

Poly(p-phenylene benzobisozazole) fiber with super strength, super modulus, and high thermal stability is a precursor and representation of macromolecule materials. PBO are rigid-rod polymer with low compressive strength and poor interface properties between the fiber and the resin, because the molecular interaction is poor. That Multi-wall carbon nanotubes/Poly(p-phenylene benzobisozazole) (MWNTs/PBO) composite fibers are prepared via in-situ polymerization is an effective method to enhance the mechanical and interfacial bonding properties of PBO fiber at the same time.According to the molecule structure of PBO, four kinds of model compounds were first synthesized in poly (phosphoric acid), then the PBO polymerization mechanism was studied. In order to study the polymerization mechanism of carbon nanotubes containing carboxyl groups/Poly(p-phenylene benzobisozazole) (MWNTs-COOH/PBO) composites, the product with similar structure of PBO was synthesized based on the view of molecule design. All model compounds were characterized with FTIR, ~1HNMR, and elemental analysis. The results showed that the structure of all synthesized model compounds was consistent with the pre-designed structure.Based on the experimental results and the theoretical analysis, the formation of benzoxazole was studied. In detail, o-aminophenol firstly transformed into phosphate ester as well as ammonium salt in PPA, at the same time, benzoic acid was converted to phosphate ester; then the two monomers reacted to each other, resulting in the generation of an ester, and the acyl rapidly migrated to form amide at low temperature. At last the ring closure step was carried out under the condition of acid catalyzer and high temperature. The polymeration mechanism of PBO polymer was derived from the formation of benzoxazole, as the following description. In PPA, terephthalic acid (TPA) were first converted to phosphate ester as well as 4,6-diamino dihydroxybenzene dihydrochloride (DADHB·2HCl) were converted to phosphate ester and amine salt after removing HCl completely. Then both monomers reacted to each other, forming an ester, and the acyl rapidly migrated to form amide. In the end, the ring closure step was carried out with acid catalyzer and high temperature. During...