Synthesis and properties of poly(ether imide)s derived from 4,4′-(1,5-naphthylenedioxy)diphthalic anhydride and various aromatic diamines

A naphthalene unit-containing bis(ether anhydride), 4,4′-(1,5-naphthylenedioxy)-diphthalic anhydride, was prepared in three steps starting from the nucleophilic nitro-displacement reaction of 1,5-dihydroxynaphthalene and 4-nitrophthalonitrile in N,N-dimethylformamide (DMF) solution in the presence of potassium carbonate. High-molarmass aromatic poly(ether imide)s were synthesized using a two-stage polymerization process from the bis(ether anhydride) and ten aromatic diamines. The intermediate poly(ether amic acid)s had inherent viscosities of 0,66–1,27 dL/g. The films of poly(ether imide)s derived from some diamines, such as p-phenylenediamine, benzidine, and bis[4-(4-aminophenoxy)phenyl] ether, crystallized and embrittled during the thermal imidization process. The other poly(ether imide)s were amorphous materials and could be fabricated into transparent, flexible, and tough films. These poly(ether imide) films had yield strengths of 111–125 MPa, tensile strengths of 96–150 MPa, elongations to break of 10–38%, and initial moduli of 1,6–2,4 GPa. All of these polymers were insoluble in organic solvents, except for that derived from 2,2-bis[(4-aminophenoxy)phenyl]propane. Their T_g's were recorded in the range of 226–265°C by DSC. Thermogravimetric analysis (TG) showed that all the polymers were stable up to 535°C in both air and nitrogen atmosphere.