Synthesis and Properties of 1,4-Bis(4-aminophenoxy)naphthalene and Its Polyimides

A new diamine 1,4-bis(4-aminophenoxy)naphthalene (1,4-BAPON) was prepared through the nucleophilic displacement of 1,4-dihydroxynaphthalene with p-fluoronitrobenzene in the presence of K2CO3 in N,N-dimethylacetamide (DMAc), followed by catalytic reduction with hydrazine and Pd/C in ethanol. A series of novel aromatic polyimides containing 1,4-bis(aminophenoxy)naphthalene units was synthesized from 1,4-BAPON and various aromatic tetracarboxylic dianhydrides by the conventional two-stage procedure that included ring-opening polyaddition in a polar solvent such as DMAc, to give poly(amic acid)s, followed by thermal cyclodehydration to polyimides. Depending on the dianhydrides used, the poly(amic acid)s obtained had inherent viscosities of 0.81–1.33 dL g−1. All the poly(amic acid)s could be solution cast and thermally converted into transparent, flexible, and tough polyimide films. These polyimides had glass transition temperatures between 247–281°C. Thermogravimetric analyses established that these polymers were fairly stable up to 500°C, and 10% weight loss temperatures were recorded in the range of 521–581°C in nitrogen and 517–575°C in air atmosphere.