Reentrant Nematic and Injected Smectic Behaviour in Binary Mixtures Including Those of Terminally Non-Polar Compounds

Abstract

Some new examples of injected smectic behaviour for binary mixtures of strong terminally polar mesogens (CBs, PCHs, BCOs, and CCHs) with a range of terminally non-polar esters are presented. Variations in the strength of thc injected behaviour are discussed. Examples of S, as well as S , injection occur.Studies of mixtures of terminally non-polar 4,4-dialkyl-2'-fluoro-p-terphenyls (I) with cyano-substituted mesogens are also described and provide an example of injection of S , and S , phases.O f greater interest is the observation that binary mixtures consisting solely of homologues of (I) can exhibit reentrant nematic behaviour, providing further evidence that reentrant phenomena are not a special feature of terminally polar mesogens and their mixtures. An isomeric mixture of two compounds of structure (1) also gives an interesting case of an injected S, phase. and enhanced S, properties are recorded for other mixtures of homologues of (I).Mixtures involving alkylialkoxy analogues of (I) also provide cxamples of S,. phase injection or enhancemcnt, and in one case some evidence for injected S, behaviour.

Low-molar-mass thermotropic liquid crystals

“…I would not like the reader to presume from this that reentrant behaviour is confined to such strongly polar materials. As found by Chan et al (1987), reentrant behaviour occurs wit 2'-fluoro-/?-terphenyls confirming earlier results by Diele al. (1983) that term inally non-polar systems also exhibit this behaviour.…”

“…Successful host materials came eventually from the mbf esters (12) of BDH Ltd (Bishop 1986) and later from fluorinated terphenyl systems (15 and 16) of Hull. The best chiral dopants were 2-octyl esters such as 13 , followed by superior cyanohydrin esters (17) developed at Hull and first reported by Gray in 1987 at the Rank Prize Funds Symposium, Ledbury, U.K. (Gray 1987.…”

“…It is noted next that spin-off between fundamental science and materials-driven research can work both ways. During a basic study (Chan et al 1987) of the effect of lateral fluorosubstitution on the properties of dialkylterphenyls (14; R and R ' are alkyl) and reentrant phase behaviour in non-terminally polar mixtures, homologous series of these materials were made, and while maintaining R ' constant at say C3H 7, R was varied from 1 to 11. It was noted that a weak, parabolic injection of Sc phases occurred for medium length R groups.…”

Mechanical Rotor-Bearing Model for Liquid Crystal Systems

“…, in each pair, the isomer with smaller deviation of G from S is always stable compare to that of larger one but one exception in case of pair of 40.clF 7. and 40.crF.7.…”

From the discovery of the partially bilayer smectic A phase to blue phases in polar liquid crystals

“…[166] Commonly N re phase is accompanied by the SmA d phase, but Gray observed it in a small concentration range in the bicomponent mixture of dialkylterphenyls having the SmA 1 phase. [167] 5. Induced N phase 5.1 Induced N phase in polar mixtures of SmA 1 -SmA 1e Polar smectics A 1 , A d , A 2 belong to the same group of symmetry; therefore, they should mix themselves in all concentration range, and if molecular interactions may be considered as ideal, the border line may be calculated from CSL equation.…”