Synthesis and properties of polyimides containing tetraphenylnaphthalene units

Aromatic polyimides (PI1x) with a tetraphenylnaphthalene unit between ether linkages were synthesized from 1,4-bis[4-(aminophenoxy)phenyl]-2,3-diphenylnaphthalene (1) and various tetracarboxylic dianhydrides by a conventional two-step procedure that included ring-opening polymerization in N-methyl-2-pyrrolidone and subsequent thermal cyclic dehydration. PI1x were characterized by X-ray diffraction, differential scanning calorimetry, thermogravimetry, and dynamic mechanical analysis. PI1x had glass transition temperatures in the range of 270–315°C and all PI1x were amorphous. The structure–property relationships of these PIs were examined and compared with those of polyimides (PI2x) from 4,4′-bis(4-aminophenoxy)biphenyl (2) and polyimides (PI3x) from 1,4-bis(4-aminophenyl)-2,3-diphenylnaphthalene (3). Water absorption and dielectric constants (ε) of the PIs were also compared and discussed on the basis of imide content per repeating unit.