No abstract

No abstract

No abstract

SUMMARY: Two chiral terephthalic acids were synthesized from (S)-2-methylbutane-1-thiol and bromoterephthalic acid or 2,5-dibromoterephthalic acid. A series of chiral polyesters was then prepared by polycondensation of silylated 4,49-dihydroxybiphenyl and mixtures of 2,5-bis(dodecylthio)terephthaloyl chloride and 2,5-bis((S)-2-methylbutylthio)terephthaloyl chloride. The copolyesters were characterized by elemental analyses, viscosity, DSC and X-ray measurements, and optical microscopy. Depending on the reaction conditions low and high molecular weights were obtained. In addition to a solid sanidic phase these polyesters form a chiral sanidic LC-phase and a chiral nematic LC-phase. However, in contrast to a normal cholesteric melt, these polyesters did not form a Grandjean texture but display the unusual "sausage texture".

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 (Tm) ≥ 200°C. A broad enantiotropic nematic or cholesteric phase is formed above Tm with isotropization temperatures (Tis) in the range of 275–325°C. Yet, the Tm 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