Synthesis and Properties of New Aromatic Polyimides Based on 2,6-Bis(4-aminophenoxy)naphthalene and Aromatic Tetracarboxylic Dianhydrides

Abstract

A series of new aromatic polyimides containing bis(phenoxy)naphthalene units were synthesized from 2,6-bis(4-aminophenoxy)naphthalene (2,6-BAPON) and various aromatic tetracarboxylic dianhydrides by the conventional two-stage procedure with thermal imidization of poly(amic acid) films. The intermediate poly(amic acid)s obtained had inherent viscosties of 1.60–3.31 dL/g, and they could be solution cast and thermally converted into transparent, flexible, and tough polyimide films. The resulting polyimide films had tensile moduli of 1.5–2.3 GPa, tensile strengths of 105–124 MPa, and elongations at break of 7–22%. The polyimide derived from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) was readily soluble in polar aprotic solvents. The glass-transition temperatures of these polyimides, except for that from pyromellitic dianhydride (PMDA), were recorded between 255 and 295 °C by differential scanning calorimetry (DSC). The softening temperatures of all the polyimide films stayed within 246–286 °C according to thermomechanical analysis (TMA). Thermogravimetic analyses (TGA) established that these polymers were fairly stable up to 500 °C, and the 10% weight loss temperatures were recorded in the range of 543–563 °C in nitrogen and 535–563 °C in air atmosphere.