Synthesis and properties of novel aromatic polyimides of 2,3-bis(4-aminophenoxy)naphthalene

Novel aromatic polyimides containing bis(phenoxy)naphthalene units were synthesized from 2,3-bis(4-aminophenoxy)naphthalene (BAPON) and various aromatic tetracarboxylic dianhydrides by the usual two-step procedure that included ring-opening polyaddition to give poly(amic acid)s, followed by cyclodehydration to polyimides. The poly(amic acid)s had inherent viscosities between 0.61-2.13 dL/g depending on the tetracarboxylic dianhydrides used. All the polyimides afforded transparent and flexible films. Almost all of the polyimides were soluble in a wide range of organic solvents such as N-methyl-2-pyrrolidone, m-cresol, and o-chlorophenol. The polyimide prepared from pyromellitic dianhydride was semicrystalline, whereas the other polyimides showed amorphous patterns in X-ray diffraction studies. Tensile strength an delongation at break of the BAPON-based polyimide films ranged from 75-96 MPa and 3-6%, respectively. These polyimides had glass transition temperatures between 226-316 deg C. Thermal analysis indicated that these polymers were fairly stable. The 10% weight loss temperatures were recorded in the range 523-578 deg C in nitrogen and 518-569 deg C in air atmosphere.