Liquid-crystalline dimers containing cholesteryl groups and azobenzene moieties with branched allyl chain: synthesis and properties

Bent-Structure Liquid Crystalline Dimers Containing a Cholesteryl Group Exhibiting Blue Phases

“…Usually, a large amount of solvent was added and then the treated clear solution was sealed and let set for several days or even weeks at room temperature to obtain pure crystals. This is mainly because the biaxial structure of the dimeric compound makes it difficult to arrange regularly, leading to poor crystallizability; the sample can be subcooled to the glass state directly during the cooling process . Nevertheless, attributed to the poor crystallizability, it is easy to obtain many mesomorphic properties of these dimeric compounds at a relatively low temperature.…”

“…This is mainly because the biaxial structure of the dimeric compound makes it difficult to arrange regularly, leading to poor crystallizability; the sample can be subcooled to the glass state directly during the cooling process. 29 Nevertheless, attributed to the poor crystallizability, it is easy to obtain many mesomorphic properties of these dimeric compounds at a relatively low temperature. For example, we can obtain the information on the layered structure of the smectic phase exhibited at room temperature with XRD, as shown in Figure 4.…”

Liquid crystalline dimers containing a cholesteryl benzoate unit: smectic phase, chiral nematic phase and blue phase

“…What is more remarkable is that it shows some significant characteristics: chirality is the driving force for helical formation and the helical structure of materials is the reason for the stability of some mesophases, such as blue phases, etc.. 15 The frustrated phase (TGB) transition is generally from the isotropic or chiral nematic phase to the chiral smectic A or chiral smectic C phase. In a previous review, Channabasaveshwar V. 15 summarized the abundance of cholesterolbased dimeric liquid crystals connected to mesogenic units such as Schiff base, 31 azobenzene, [32][33][34] tolane, 35 chalcone, 36 and stilbene 37 through flexible chains. Numerous experiments have demonstrated the abundance of mesophases of cholesterol-based dimers, the ability of chirality of which tends to stabilize some frustrated phases.…”