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Synthesis and Characterization of Poly(amide-imide)s Based on 1,7-Bis(4-aminophenoxy)naphthalene and Various Bis(trimellitimide)s

Novel poly(amide-imide)s III containing a 1,7-bis(phenoxy)naphthalene unit were synthesized by 1,7-bis(4-aminophenoxy)naphthalene (1,7-BAPON) and various bis(trimellitimide)s in N-methyl-2-pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents through direct polycondensation. The polymers were obtained in quantitative yield with inherent viscosities of 0.48—0.91 dL g−1. Most of the polymers were soluble in aprotic dipolar solvents such as N,N-dimethylacetamide (DMAC) and NMP, and could be solution cast into transparent, flexible, and tough films. The films had yield strength of 85—97 MPa, tensile strength of 73—103 MPa, elongation at break of 9—69%, and initial modulus of 1.89—2.35 GPa. Wide-angle X-ray diffraction revealed that most polymers III are amorphous. The glass transition temperatures of some polymers could be determined by differential scanning calorimetry (DSC) traces, recorded at 213—250°C. The 10% weight loss temperatures of the polymers were in the range of 514—579°C in nitrogen, and char yields of polymers at 800°C in nitrogen were higher than 50%.