Synthesis and properties of soluble copolyimide based on PBAP-ODPA-BPADA

Three kinds of polyimides were synthesized via the conventional two-step thermal or chemical imidization process by using 4-phenyl-2,6-bis(4-aminophenyl)pyridine(PBAP)as the diamine monomer,4,4′-oxydiphthalic dianhydride(ODPA)and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride(BPADA)as the dianhydride monomer in dimethylformamide(DMF).The structure of the polymers were characterized by FTIR.The results showed that there were characteristic peaks of polyimides around 1 780、1 720 and 725 cm-1.The properties of the products were measured by solubility tests,X-ray diffraction,thermogravimetric analysis,tensile tests and water uptake tests.The resulting copolyimide was soluble in common organic solvents.They had good thermal stability with decomposition temperatures at initial above 500 ℃,the temperature at 10% weight loss of 547.1～601.5 ℃ and the residue at 800 ℃ of 64.8%～67.2% in nitrogen atmosphere.The polyimide films had tensile strengths,tensile modulus,and elongations at break in the ranges 105.8～112.6 MPa,2.24～2.32 GPa,and 9.5%～10.2% respectively.These films also possessed low water uptakes of 0.96%～0.98%.