New polymer syntheses 22. LC-poly(esterimide)s derived from trimellitic acid, ω-amino acids and hydroquinone or 4,4′-dihydroxybiphenyl

Diacids with variable spacer length were prepared by condensation of trimellitic anhydride and ω-amino acids. From these diacids, homopolyesters were prepared by thermal condensation with the acetates of hydroquinone or 4,4′-dihydroxy biphenyl and a series of copolyesters containing 4-hydroxy benzoic acid. The same LC poly(ester imide)s could also be prepared in a “one-pot procedure” from trimellitic anhydrid, lactams, and bisphenol acetates. The differential scanning calorimetry (DSC) traces of most poly(ester imide)s exhibit two endotherms representing the solid → LC phase transition (Tm₁) and the LC phase → isotropic melt transition (Tm₂). Observation under the polarizing microscope and wide-angle X-ray scattering (WAXS) measurements suggest that the LC phase formed immediately above the melting points (Tm₁) have a smectic character. Poly(ester imide)s of 4,4′-dihydroxybiphenyl possess higher melting points and a broader temperature range of the LC phase than those of hydroquinone. The copolyesters possess a nematic melt over a broad temperature range. Thermomechanical analyses under low pressure (0.05 kg/mm²) gave heat distortion temperatures close to the melting points (Tm₁), and under high pressure (1 kg/mm²), values between Tm₁ and the glass transition temperatures (T_g). Thermogravimetric measurements indicate that processing from the melt is feasible up to temperatures around 340°C.