Binary systems of smectics A with enhanced nematic phase

Abstract

Résumé. 2014 On a établi le diagramme de

High Birefringence Liquid Crystals

“…Some cases were demonstrated where smectic phases were strongly destabilized and the range of nematic phase was enhanced, or nematic phase was created only from smectic compounds. That could be noticed in isothiocyanates mixtures (smectic A 1 ) [53,54] and mixtures of isothiocyanates (smectic A 1 or smectic E) and cyanides (smectic A d ) [55][56][57]. Both components are polar and must differ with the lengths of molecules meaningfully.…”

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

“…While observing the mesogenic behaviour of compounds with Z = NO 2 , the presence of SmA 2, SmA 1 and SmA d phases without the N re phase in the phase sequence has been confirmed, and the SmA 2 phase has been observed in one specific case only -when dipoles of both the central bridge groups X and Y and the terminal group Z have been directed in the opposite directions: ←, ←, → (i.e. see compounds [37][38][39]41).…”

“…It is sometimes as low as 0.9·l for two-ring molecules with a short chain. [37][38][39] The layer spacing, d, however, approaches l for molecules with a longer chain (n ≥ 8). In three-ring molecules, the smectic layer spacings are a little more expanded.…”

Binary Smectic Systems Including Trinuclear Pyrimidines with and without Nematic Gap

“…In earlier works [1,2] it was shown that in binary mixtures composed of compounds with polar terminal groups forming A[ and A d smectic phases a nematic gap is observed which separates a smectic A| region with an excess of one component from a smectic A d region with an excess of the other component. So far this behaviour was observed for pairs of compounds for which the smectic layer spacing ratio is at least 1.36.…”

“…(ii) is the nematic gap observed if the above condition is fulfilled together with other conditions so far unknown? The binary mixtures showing a nematic gap which is not accompanied by an enhancement of the smectic phase included one of the following compounds: isothiocyanatophenyl alkylbenzoate or alkylcyclohexylbenzoate, or else 5-alkyl-2-(p-isothiocyanatophenyl)-l,3-dioxane (all smectics A,), and one of the following compounds: cyanophenyl or nitrophenyl alkylcyclohexylbenzoate, or else 4-alkoxy-4-cyanobiphenyl (smectics A d ) [1,2]. A common feature of these compounds is the presence of two polar groups located in the terminal and central Reprint requests to Prof. R. Dabrowski, Military Technical Academy, 01-489 Warschau, Polen.…”