Synthesis and characterization of some new thermally stable polyimides and copolyimides bearing bipyridine side-chain groups

A new series of polyimides and copolyimides were synthesized via reaction of new bipyridine containing diamine, 4, 6-bis(4-aminophenyl)-2, 2′-bipyridine, with commercial dianhydrides. 4, 6-bis(4-aminophenyl)-2, 2′-bipyridine was synthesized starting from condensation reactions of 4-nitro acetophenone, 4-nitrobenzadehyde and pyridacyl pyridinium iodide (Krönke salt) and reduction of the desired dinitro compound. The synthesized monomer and polymers were characterized by FT-IR, NMR and CHN elemental analysis. The physical properties of the polymers, including solubility and viscosity were studied, and the results showed acceptable solubility and good chain growth for polymers. Thermal stability of these polymers was also studied by Thermo Gravimetric Analysis (TGA). The polymers start to lose weight because of thermal degradation at about 300 °C. From Differential Scanning Calorimetry (DSC), the polymers were showed T_g between 190 and 230 °C. The morphology of these polymers was also investigated by X-ray Diffraction (XRD), and the results showed only broad reflections originated from their low crystallinities.