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 ( Tm 1 ) and the LC phase → isotropic melt transition ( Tm 2 ). Observation under the polarizing microscope and wide‐angle X‐ray scattering (WAXS) measurements suggest that the LC phase formed immediately above the melting points ( Tm 1 ) 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/mm 2 ) gave heat distortion temperatures close to the melting points ( Tm 1 ), and under high pressure (1 kg/mm 2 ), values between Tm 1 and the glass transition temperatures ( T g ). Thermogravimetric measurements indicate that processing from the melt is feasible up to temperatures around 340°C.