Layer structures. VI. Chiral sanidic polyesters derived from 2,5-bis (dodecyloxy) terephthalic acids and 4,4′-dihydroxybiphenyl

Copolycondensations of (S,S)-2,5-bis(2-methylbutyloxy) terephthaloylchloride with 2,5-bis(dodecyloxy)terephthaloylchloride and with 4,4′-bistrimethylsiloxybiphenyl yielded a series of novel chiral thermotropic copolyesters. These polyesters were characterized by elemental analyses, inherent viscosities, ¹H-NMR spectroscopy, optical rotations, optical microscopy, DSC measurements, and WAXS powder patterns recorded with synchrotron radiation under variation of the temperature. All homo- and copolyesters formed a solid sanidic layer structure with melting temperatures (T_m) ≥ 200°C. A broad enantiotropic nematic or cholesteric phase is formed above T_m with isotropization temperatures (T_is) in the range of 275–325°C. Yet, the T_m of the chiral homopolyester is so high (378°C) that the melting process is immediately followed by rapid degradation. The cholesteric phases of the copolyesters displayed unusual mobile schlieren textures, but a stable Grandjean texture was never obtained. Cholesteric domains consisting of loose bundles of more or less helical main chains are discussed as supramolecular order responsible for the observed textures and their pronounced temperature dependence. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 947–957, 1997