Anomalous Temperature Dependence of Elastic Constants in the Nematic Phase of Binary Mixtures Made of Rodlike and Bent-Core Molecules

Abstract

We report on two anomalous trends in the temperature dependences of the splay (K11) and bend (K33) elastic constants in the nematic (N) phase of mixtures of compounds with rodlike (R) and bent-core (BC) molecules: As the sample is cooled from the isotropic to N transition point, (i) K33 increases, attains a maximum value and then decreases, and (ii) close to the N to smectic A (SmA) transition point, K11 decreases sharply. At higher temperatures the bow axes of BC molecules are aligned along the director n, strongly favoring a bend distortion of n as the orientational order parameter is increased. Close to the N-SmA transition point the smecticlike short-range order builds up, and the arrow axes of BC molecules are aligned along n, facilitating a splay distortion of n. A simple model calculation brings out the anomalous trend in K33.

Effect of cybotactic clusters on the elastic and flexoelectric properties of bent-core liquid crystals belonging to the same homologous series

“…Dodge et al [30,31] showed that by mixing small amounts of bent-core systems in a calamitic nematic (8OCB) provided it is dissolvable, K 33 is significantly reduced. Kundu et al [32] made similar findings for calamitic 8OCB mixed with different concentrations of bent-core LCs in the nematic phase but they additionally obtained somewhat anomalous results for the elastic constants. They found that closer to the nematic-smectic phase transition temperature both K 11 and K 33 first decrease and then increase slightly with a reduction in temperature, in contrast to both of these elastic constants increasing significantly closer to the nematicsmectic phase transition temperature in the host 8OCB.…”

“…They found that closer to the nematic-smectic phase transition temperature both K 11 and K 33 first decrease and then increase slightly with a reduction in temperature, in contrast to both of these elastic constants increasing significantly closer to the nematicsmectic phase transition temperature in the host 8OCB. In recent investigations, measurement of these constants in pure BCNs in nematic phase has also yielded intriguing results, K 33 is found in most cases to be lower than K 11 [24,25,[32][33][34].…”

Hierarchical elasticity of bimesogenic liquid crystals with twist-bend nematic phase

“…2 These elastic behaviors are reminiscent of those in the vicinity of nematic to smectic-A or smectic-C phase transition in bent-core systems. 23,24 The abnormal tendency in K 33 was explained by smectic short-range fluctuations as the temperature decreased. 2,24 The focal-conic and parabolic defect textures were observed in both the smectic and N tb phases.…”

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

“…The BLC medium showed various new physical properties and suggested important clues for understanding the underlying physics in the condensed matter [1][2][3][4]. The BLC also has a great potential of new electro-optical applications [5][6][7][8][9][10][11][12][13]. For example, some BLC molecules were found to have a larger flexoelectric effect than the conventional rodlike liquid crystal (LC) molecules [5][6][7][8][9].…”

“…The BLC also has a great potential of new electro-optical applications [5][6][7][8][9][10][11][12][13]. For example, some BLC molecules were found to have a larger flexoelectric effect than the conventional rodlike liquid crystal (LC) molecules [5][6][7][8][9]. Some BLC molecules were reported to have a strong nonlinear optical effect [10][11][12][13].…”