LIQUID-CRYSTALLINE POLYIMIDES .3. FULLY AROMATIC LIQUID-CRYSTALLINE POLY(ESTER IMIDE)S DERIVED FROM N-(4-CARBOXYPHENYL)TRIMELLITIMIDE AND SUBSTITUTED HYDROQUINONES

Three imidodicarboxylic acids were prepared from trimellitic anhydride and 4-aminobenzoic acid, 2-chloro-4-aminobenzoic acid, or 3-chloro-4-aminobenzoic acid. These dicarboxylic acids were condensed with acetyl derivatives of methyl-, chloro-, bromo-, or phenylhydroquinone, with mono- or bis(phenylthio)-hydroquinone, or with 2,5-diphenoxyhydroquinone. The resulting poly(ester imide)s were characterized by elemental analyses, C-13 NMR spectra, inherent viscosities, and DSC and WAXS measurements by optical microscopy with polarized light and by thermogravimetric analyses; polyesters derived from methyl-, chloro-, and bromohydroquinone have melting points in the temperature range 345-365-degrees-C, but their birefringent melt does not flow. Polyesters derived from phenyl- and (phenylthio)hydroquinone are also semicrystalline but form a mobile nematic melt. Polyesters derived from 2,5-bis(phenylthio)- or 2,5-diphenoxyhydroquinone are amorphous and only form an isotropic melt. The chlorine substituents in the imidodicarboxylic acid reduce both crystallinity and stability of the mesophases. In addition to homopolyesters, three copolyesters containing two different hydroquinones were synthesized and characterized.