(S)-((2-Methylbutyl)thio)hydroquinone was prepared from benzoquinone and (S)-2-methylbutyl mercaptan. One series of cholesteric copolycarbonates was prepared from this chiral hydroquinone, methylhydroquinone, and 4,4‘-dihydroxybiphenyl by interfacial polycondensation with diphosgene. All copolycarbonates were noncrystalline and decomposed upon heating above 250 °C. A Grandjean texture was only observed for one sample. A second series of cholesteric copolycarbonates was prepared from isosorbide, methylhydroquinone, and 4,4‘-dihydroxybiphenyl. Four different polycondensation methods were studied and compared in this case. The best results were obtained by polycondensation in pyridine containing organic cosolvents. Two copolycarbonates of isosorbide were obtained which formed a broad cholesteric phase with a Grandjean texture.

Three series of randomly branched copolyesters were prepared from mixtures of acetylated trimethylsilylesters of non‐toxic natural hydroxy acids. The first series is based on 1 : 1 molar ratio of β‐(4‐hydroxyphenyl)propionic acid (HPPA, phloretic acid) and 4‐hydroxybenzoic acid (4‐HBA). The second series was prepared from HPPA, 4‐HBA and vanillic acid (VA, molar ratio 1 : 1 : 1), and in the third series VA was replaced by 4‐hydroxycinnamic acid (HCA). The branching density was varied via the feed ratio of triacetylgallic acid. The stability of the nematic phase increases with decreasing branching density, but a partial LC‐character was found even at relatively short length of the linear chain segments. Finally, two star‐shaped and hyperbranched copolyesters were prepared. The incorporation of a star center type molecule allowed the control of the molecular weight, but eliminated the liquid‐crystalline character almost completely. The ternary copolyesters and the quaternary copolyesters of VA were characterized by dynamic rheological measurements, and in the latter case also a few stress‐strain measurements were conducted.

4-Propargyloxy benzoic acid, 6-propargyloxy-2-naphthoic acid and 4′-propargyloxybiphenyl-4-carboxylic acid were synthesized from the corresponding hydroxy acids and converted into the acid chlorides. Diesters were then prepared by the reaction of these acid chlorides with diphenols such as hydroquinone, methylhydroquinone n-octylthiohydroquinone and phenylhydroquinone. Most of these diesters form an enantiotropic nematic melt but some diesters form a monotropic liquid crystal phase. Cholesteric phases were observed for diesters of ( S)-2-methylbutylthiohydroquinone. Diesters derived from 6-propargyloxy-2-naphthoic acid begin to crosslink above 200 °C with an optimum cure temperature of 240–250 °C. The crosslinking of the 4′-propargyloxybiphenyl-4-carboxylic acid derivatives occurs at a temperature 60 °C higher. Several diesters crosslink in the nematic state, but most of them undergo isotropization before completion of the crosslinking process. Numerous cholesteric blends of nematic diesters and chiral diesters of isosorbide were studied and Grandjean textures with bright colours were found. Thermal crosslinking in the cholesteric phase was feasible in several cases.

Four series of liquid‐crystalline copolyesters were prepared by the transesterification of poly(ethylene terephthalate) (PET) with 4‐acetoxybenzoic acid (4‐ABA) or mixtures of 4‐ABA and acetylsalicylic acid (ASA). Two series consisted of 30 mol % PET, and the other two series consisted of 40 mol % PET. The molar ratio of 4‐HBA and ASA was varied in all four series from 0 to 25 mol %. One 30% PET series and one 40% PET series were prepared with the addition of acetic acid, which caused a more perfect randomization of the sequence but yielded slightly lower molecular weights. The incorporation of ASA reduced the crystallinity, which vanished completely at a salicylic acid (SA) content greater than 10 mol %. SA also reduced the stability of the nematic phase, but all the copolyesters were thermotropic up to a 20 mol % SA content. Furthermore, the molecular weights decreased with the increasing incorporation of ASA. Despite this negative trend, the melt viscosity and the storage and loss moduli passed a maximum between 5 and 10% SA. Obviously, the incorporation of SA favored the formation of entanglements. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2013–2022, 2000

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