排序方式: 共有33条查询结果,搜索用时 15 毫秒
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R. Balachandran V. P. Panov Yu. P. Panarin M. G. Tamba G. H. Mehl J. K. Song 《Molecular Crystals and Liquid Crystals》2015,611(1):65-70
The effective flexoelectric coefficient and flexoelectric polarization are investigated for a bimesogenic liquid crystal CBC11CB with a twist bend nematic phase (Ntb). The effective flexoelectric coefficients for CBC11CB in the ordinary nematic phase (N) are obtained to be much larger in comparison to conventional calamitics, and is almost twice higher for CBC11CB than that reported for another odd symmetric bimesogen. The flexoelectric polarization (Pf) in the N phase is found to be almost 2.5 times higher than in rod-like molecules. Additionally, Pf is obtained to be much larger in the Ntb phase than in the nematic phase. 相似文献
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Dong-Jin Lee Jun-Chan Choi Min-Kyu Park Ji-Sub Park Amid Ranjkesh Hyun Chul Choi 《Liquid crystals》2017,44(8):1321-1331
We proposed an optical measurement method for determination of flexoelectric polarisation change in liquid crystals (LCs), which can be induced in highly distorted LC geometries. A hybrid-aligned nematic LC (NLC) mode was introduced to evaluate the direction and magnitude of the flexoelectric polarisation. We measured the DC offset amounts for equivalent brightness levels between forward and reverse bias vertical electric fields to estimate the sign and magnitude of es?eb of flexoelectric coefficients. Additionally, the optical incident angle (αmax) for the maximum effective birefringence was investigated to predict the depth distribution of the LC director affecting the magnitude of the flexoelectric polarisation. The relationship between the variations of the DC offset and αmax by the flexoelectric polarisation changes was examined using the NLC mixtures doped with three selected bent-core LCs. 相似文献
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ABSTRACTThe field of liquid crystals is truly multidisciplinary with numerous examples of virtuous circles of interaction between chemistry, physics, theory and engineering resulting in breakthroughs in both fundamental understanding and novel applications. This paper, written to mark John Goodby’s 65th birthday, offers a personal perspective of the synergy between chemistry and physics from a collaboration that has spanned three decades. The first part of the paper reviews some of the physics insights that resulted from chiral liquid crystals fundamental to understanding structures in ferroelectric, ferrielectric and antiferroelectric systems. The second part of the paper describes some of the remarkable consequences of the anomalous elasticity and flexoelectricity found in the nematic phases of bent-core materials. In particular, we present unusual bowing of disclination lines in the nematic phase of a bent-core material in the presence of a field. Finally, the paper summarises some future prospects relating for bent-core materials. The paper by no means captures the amazing breadth of contribution that John’s chemistry has made to the subject, but aims to exemplify how his generous collaborative approach coupled with innovative chemistry and physical insight has led to paradigm changes in our subject. 相似文献
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Theoretical analysis of the influence of flexoelectric effect on the defect site in nematic inversion walls
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Based on the experimental phenomena of flexoelectric response at defect sites in nematic inversion walls conducted by Kumar et al., we gave the theoretical analysis using the Frank elastic theory. When a direct-current electric field normal to the plane of the substrate is applied to the parallel aligned nematic liquid crystal cell with weak anchoring, the rotation of ± 1 defects in the narrow inversion walls can be exhibited. The free energy of liquid crystal molecules around the +1 and-1 defect sites in the nematic inversion walls under the electric field was formulated and the electric-field-driven structural changes at the defect site characterized by polar and azimuthal angles of the local director were simulated. The results reveal that the deviation of azimuthal angle induced by flexoelectric effect are consistent with the switching of extinction brushes at the +1 and-1 defects obtained in the experiment conducted by Kumar et al. 相似文献
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Deformations of nematic layers caused by magnetic field allow determination of the elastic constants of liquid crystal. In
this paper, we simulated numerically the deformations of planar and homeotropic nematic layers. The flexoelectric properties
of the nematic and presence of ions were taken into account. Our aim was to show the influence of flexoelectricity on the
results of the real measurement of the elastic constants k33 and k11. In these simulations, we calculated the optical phase difference ΔΦ between the ordinary and extraordinary rays of light
passing through the layer placed between crossed polarizers as a function of the magnetic field induction B. One of the elastic
constants can be calculated from the magnetic field threshold for deformation. The ratio k33/k11 can be found by means of fitting theoretical ΔΦ(B) dependence to the experimental results. The calculations reveal that the
flexoelectric properties influence the deformations induced by the external magnetic field. In the case of highly pure samples,
this may lead to false results of measurement of the elastic constants ratio k33/k11. This influence can be reduced if the nematic material contains ions of sufficiently high concentration. These results show
that the flexoelectric properties may play an important role, especially in well purified samples. 相似文献
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I. V. Kotov M. V. Khazimullin A. P. Krekhov 《Molecular Crystals and Liquid Crystals》2013,570(1):885-892
Abstract The stability of the equilibrium configurations of a nematic liquid crystal confined between two coaxial cylinders is analysed when a radial electric field is applied and the flexoelectric effect is taken into account. The threshold for perturbations depending only on the radius r in the cylindrical coordinate system and strong boundary conditions is studied. A new type of orientational transition caused by pure flexoelectric effect is found. 相似文献
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