Synthesis and characterization of novel polyimides derived from 3,6-bis(4-aminophenoxy)pyridazine

Pyridazine-containing aromatic diamine monomer, 3,6-bis(4-aminophenoxy)pyridazine (APPD), was successfully synthesized by a nucleophilic substitution reaction of 3,6-dichloropyridazine with para-aminophenol. The aromatic heterocyclic diamine was employed to synthesize a series of polyimides (PIs) by polycondensation with various commercially available aromatic dianhydrides in N,N-dimethylacetamide via the conventional two-step method and further thermal imidization forming polyimides. The inherent viscosities of the resulting poly (amic acid)s were in the range of 0.47-1.51 dL g(-1). Meanwhile, strong and flexible PI films were obtained, which had good thermal resistance, with the glass transition temperatures of 214-305 degrees C and the temperature at 5% weight loss of 421-463 degrees C under nitrogen atmosphere, as well as outstanding mechanical properties with tensile strengths of 61-102 MPa and elongations at break of 2.8-64.7%. The cutoff wavelength of the PI films were ranged in 357-413 nm.