Synthesis and properties of polyimides derived from 1,6‐bis(4‐aminophenoxy)naphthalene and aromatic tetracarboxylic dianhydrides

Abstract 1,6‐Bis(4‐aminophenoxy)naphthalene (I) was used as a monomer with various aromatic tetracarboxylic dianhydrides to synthesize polyimides via a conventional two‐stage procedure that included ring‐opening polyaddition in a polar solvent such as N,N‐dimethylacetamide (DMAc) to give poly(amic acid)s, followed by thermal cyclodehydration to polyimides. The diamine (I) was prepared through the nucleophilic displacement of 1,6‐dihydroxynaphthal‐ene with p‐chloronitrobenzene in the presence of K2CO3, followed by catalytic reduction. Depending on the dianhydrides used, the poly(amic acid)s obtained had inherent viscosities of 0.73–2.31 dL/g. All the poly(amic acid)s could be solution cast and thermally converted into transparent, flexible, and tough polyimide films. The polyimide films had a tensile modulus range of 1.53–1.84 GPa, a tensile strength range of 95–126 MPa, and an elongation range at break of 9–16%. The polyimide derived from 4,4′‐sulfonyldiphthalic anhydride (SDPA) had a better solubility than the other polyimides. These polyimides had glass transition temperatures between 248–286°C (DSC). Thermogravimetric analyses established that these polymers were fairly stable up to 500°C, and the 10% weight loss temperatures were recorded in the range of 549–595°C in nitrogen and 539–590°C in air atmosphere.