Study On Design,Synthesis And Properties Of High Performance Polymers Containing 4,5-diazafluorene

High performance polymer is a polymer that can maintain high strength,high modulus and other physicochemical properties even under high temperature conditions.Because of its lightweight and easy processing,it has been widely used in aerospace,automotive manufacturing,electronic information and other fields.The development and preparation of new high-performance polymer materials are of great social and economic importance.For high-performance polymers that are widely used at present,many drawbacks such as poor dissolution processability while ensuring high heat resistance and mechanical properties,still limit their widely applications.The research and development of high-performance polymers with good dissolution processing properties,excellent thermal stability and mechanical properties are of great significance for reducing material costs,broadening processing windows,and application fields.Diazafluorenen is a derivative of anthraquinone.The Introducing of dizafluorene into a polymer can significantly improve the solubility,heat resistance,refractive index,and birefringence of the resulting polymer.In this dissertation,a novel dianhydride monomer and a diacid monomer were prepared from the non-coplanar diazafluorene structure,and the corresponding polyimide and polybenzimidazole high performance polymers were obtained.The related properties of prepared polymers were characterized and fully discussed.（1）An acid anhydride monomer containing diazafluorene structure was designed and successfully synthesized.Four types of polyimides soluble in common solvents were prepared from the new monomer and four aromatic diamines.The properties of polyimide brought by the introduction of diazafluorene structure were discussed in detail by UV-vis spectroscopy,thermogravimetry,and solubility tests.The results demonstrated that the introduction of diazafluorene form this novel dianhydride can effectively improve the solubility of polyimides.Some of them even can partially dissolved in low boiling temperature solvents such as 1,4-dioxane and tetrahydrofuran after heating.Meanwhile,these polyimides also maintained excellent thermal stability and high mechanical strength.The glass transition temperature was between 270 ^oC and311 ^oC,the 10%weight loss(T_10%)was between 387 ^oC and 520 ^oC,and the tensile strength was between 92 MPa and 105 MPa.In addition,the obtained polyimides exhibited excellent light transmission properties,while having outstanding low dielectric constant（2.78³.38）,and low water absorption（2.8%⁴.9%）.（2）A diacid monomer9,9-（2,7-dicarboxylhydrazino）-4,5-diazafluorene was synthesized and polymerized with biphenyltetramine to obtain a polybenzimidazole with superior dissolution property.Polybenzimidazole was further studied as a novel high temperature proton exchange membrane after doping with phosphoric acid.The results show that,due to the introduction of the diazafluorene structure,the excellent thermal stability and mechanical properties of polybenzimidazole are achieved while the dissolution properties of the material are greatly improved.All the films maintained excellent thermal stability(T_5%215 ^oC²38 ^oC,T_10%273 ^oC⁴02^oC),high mechanical properties,tensile strength（13 MPa¹35 MPa）,elongation at break Rate（3.4%⁴7%）;Through the anti-oxidation stability test,the phosphoric acid-doped film was kept in the Fenton reagent for 120 h without failure;The doping level reached 9.70 and the proton conductivity was 0.023 S/cm at 180 ^oC after dopping with phosphoric acid at a concentration of 7mol/L.