Gray cyanobiphenyl nematics

Figure 24. Biomesogenic structures a) (Bio)meso-gens displaying order-disorder distributions in CPK-presentation (left to right and top to bottom) hexa-n-alkanoyl-oxybenzene discoid - Chandrasekar s first non-rodlike liquid crystal [28 a, 51c] enantiomeric cholesteric estradiol- and estrone-derivatives [ 17 a, c, d, 26 f, 51 a, s, u] Reinitzer s cholesterolbenzoate [21, 22] - together with the acetate the foundation stones of liquid crystal history [21, 22] Kelker s MBBA -first liquid crystal fluid at ambient temperature [ 13 f, g] Gray s cyanobiphenyl nematics for electrooptic displays [25 a, 51 e] lyotropic lecithin membrane component [7 a, 14, 27 d, 52 a] and valinomycin-K -membrane carrier [7 a, 35] thermotropic cholesteryl-side-chain-modifiedpolysiloxanes with the combination of flexible main-chain and side-chain spacers [51 a, h] thermotropic azoxybenzene polymers with flexible main-chain spacers [51a] thermotropic cya-...

The first report on the liquid crystalline properties of these compounds was published by Gray and Mosley [44] in 1976. The series of 4 -n-alkyl-4-cyanobiphenyls (CBn) have been widely studied by different methods due to their readily accessible nematic ranges around room temperature. The compounds have the phase sequences crystal-nematic-isotropic for CBS, CBIO, and monotropic nematic for CBS, CB4 crystal-smectic A-nematic-isotropic for CB9 crystal-smectic A-isotropic for CBll. The lower homologous CB2 is nonmesogenic. The general chemical structure of the compounds CBn is presented in Fig. 1. 

Gray describes a stable material cyanobiphenyls) with nematic phase at ambient temperature... 

Before going on to discuss briefly other basic liquid crystal phases, it is worth recording some points about the development of nematic liquid crystals, since a substantial part of this book concerns these substances. The first nematic liquid crystal, p-azoxyanisole (PAA), was synthesised by Gattermann and Ritschke [102], who reported their results in 1890 it was the first liquid crystal not based on a naturally occurring substance and went on to be extensively investigated by Lehmann and others. The first relatively stable room temperature nematic liquid crystal, 4-methoxybenzylidene-4 -butylaniline (MBBA), was synthesised by Kelker and Scheurle [142] in 1969, but, for various reasons, this substance was not considered suitable for some applications. The nematic liquid crystal 4-pentyl-4 -cyanobiphenyl (5CB) is an example of a stable room temperature material designed for use in twisted nematic displays (discussed in Section 3.7) and was synthesised by Gray and co-workers in the early 1970 some details can be found in articles [117, 118). 

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