The Nematic Phases of Bent‐Core Liquid Crystals

Abstract

Over the last ten years, the nematic phases of liquid crystals formed from bent-core structures have provoked considerable research because of their remarkable properties. This Minireview summarises some recent measurements of the physical properties of these systems, as well as describing some new data. We concentrate on oxadiazole-based materials as exemplars of this class of nematogens, but also describe some other bent-core systems. The influence of molecular structure on the stability of the nematic phase is described, together with progress in reducing the nematic transition temperatures by modifications to the molecular structure. The physical properties of bent-core nematic materials have proven difficult to study, but patterns are emerging regarding their optical and dielectric properties. Recent breakthroughs in understanding the elastic and flexoelectric behaviour are summarised. Finally, some exemplars of unusual electric field behaviour are described.

Anomalously low twist and bend elastic constants in an oxadiazole-based bent-core nematic liquid crystal and its mixtures; contributions of spontaneous chirality and polarity

“…17,18 The main structural differences between compounds 1 and 2 lie in their lateral substitution and terminal chains; the former has asymmetric methoxy-and methyl-substitution, while the latter has no lateral chains but asymmetric terminal chains. The lateral substitution serves to reduce the temperature at which the nematic phase is exhibited, 21 an important factor if any practical applications of bent-core mesogens are to be realised.…”

Optical Simulation of Viewing Angle Property of Biaxial Nematic Bent-Core Liquid Crystal

“…With this reason, the electrooptical properties of the BLC molecules for the display applications have been focused in the smectic or isotropic phases [23][24][25]. For the practical application of Nb-mode LCD, new BLC materials possessing a wide nematic phase range around room temperature should be synthesized [20]. Alternatively, mixing the BLC molecules with the conventional rodlike LC can be another solution [6][7][8][9].…”

“…(4). We referred to the general refractive indices nx and ny in the previous literatures for the Nb-LCD simulation [20,21]. The refractive indices of the VA-and the IPS-LCD were set to be ne = 1.70 and nz = 1.50.…”

Second-harmonic generation and the influence of flexoelectricity in the nematic phases of bent-core oxadiazoles

“…[20,21] The nematic phases of all the materials form at high temperatures of at least 170°C. [20][21][22] The temperatures for the phase transitions were measured by observation of the LC using polarising microscopy. The temperatures for compounds 1 and 2 were previously reported in Ref.…”