Physical Properties: Magnetic Properties of Liquid Crystals

Dunmur, D. A.; Toriyama, Kazuhisa; Demus, D.; Goodby, John W.; Gray, G. W.; Spieß, Hans Wolfgang; Vill, V.

doi:10.1002/9783527620760.ch7b

Cited by 14 publications

(18 citation statements)

References 18 publications

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“…K 1 = 7.0 × 10 −12 N, K 2 = 4.4 × 10 −12 N, K 3 = 9.7 × 10 −12 N [11], but we can anticipate that the main observations are similar for the Lebwohl-Lasher model, i.e. in the one constant approximation.…”

Section: The Simulation Modelmentioning

confidence: 74%

Effect of Surface Anchoring on Creation of Defects in a Nematic Film. A Monte Carlo Simulation

Chiccoli

Evangelista

Pasini

et al. 2015

Molecular Crystals and Liquid Crystals

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Section: The Simulation Modelmentioning

confidence: 74%

Effect of Surface Anchoring on Creation of Defects in a Nematic Film. A Monte Carlo Simulation

Chiccoli

Evangelista

Pasini

et al. 2015

Molecular Crystals and Liquid Crystals

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“…For the investigated mesogenes the second process, related to the perpendicular component of the dipole moment, is hardly seen or practically unobserved in the parallel component of ε in this frequency range [19]. This is a direct consequence of the fact that this process has a maximum above 100 MHz [20].…”

Section: Dielectric Relaxationmentioning

confidence: 77%

Prenematic Self-Assembling of Mesogenic Molecules in Isotropic Liquid and Orientational Order in Nematic Phase

et al. 2011

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Dielectric relaxation study of nematogenic 4-n-alkyl-4 -cyanobiphenyls (nCB, n = 5, 6), 4-(trans-4 -n-alkylcyclohexyl)isothiocyanatobenzenes (nCHBT, n = 6, 8), 4-cyanophenyl-4 -n-alkylbenzoates (nCPB, n = 6, 8), 4-cyano-3-fluorophenyl-4 -n-octyloxybenzoate (8OCFPB), and 4-cyanophenyl-4 -n-octyloxy-3 -fluorobenzoate (8OCPFB) was performed in the frequency range from 50 kHz to 100 MHz in the nematic and isotropic phases. The static permittivity and the relaxation process related to the rotation of molecules around their short axis was analyzed. For some of these liquid crystals anomalous temperature dependence of static permittivity in the pretransitional region of the isotropic phase was observed. Based on the Meier-Saupe-Martin model of molecular diffusion in nematics, the orientational order parameter P 2 was determined from dielectric relaxation times and retardation factor. The values of P 2 calculated from the dielectric relaxation data were compared with the results obtained from measurements of polarized electronic absorption. Correlations between the magnitude of the dielectric pretransitional effect and the orientational order in the nematic phase were discussed.

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“…There are several different ways to classify the relaxation modes of reorientation of the molecular dipoles [15,33,34]. We find it convenient to discuss the relaxation modes from the point of view of the experimental features relevant to the dielectric memory effects in director reorientation, namely, the dispersion curves for the parallel and perpendicular components of the dielectric tensor.…”

Section: Dielectric Relaxation In Liquid Crystalsmentioning

confidence: 99%

“…However, it might not hold when the driving field is switched quickly. The dielectric relaxation associated with reorientations of the dipole moments around the molecular short axis in NLCs is slow, with a typical relaxation time t that might be as large as 0.01-1 ms [15,16]. If the external field changes over a time comparable to t, it is intuitively clear that the dielectric response should depend not only on the present value of E, but also on its past values.…”

Section: Introductionmentioning

confidence: 99%

Dielectric relaxation and memory effects in nematic liquid crystals

Shiyanovskii

Lavrentovich

2010

Liquid Crystals

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Liquid crystals are fluids with anisotropic dielectric properties. Since the 1930s, when dielectric anisotropy was shown by Frederiks and Tsvetkov to cause director reorientation in an applied electric field, deepening our understanding of this property has been a leading theme in the development of liquid crystal science that culminated in the modern liquid crystal displays revolution. Saupe contributed greatly to the field by first coauthoring the molecular statistical theory of the nematic order, and then using it to explain how the nematic order affects dielectric relaxation in liquid crystals, i.e., how the components of the dielectric tensor depend on the frequency of the applied electric field. We review recent developments in the field associated with the finite rate of the dielectric relaxation, which results in a time lag of the electric displacement as compared with the instantaneous value of the electric field. This time lag causes profound effects on director reorientation when the characteristic time of the field change is close to (or smaller than) the dielectric relaxation time. We review recent experimental and theoretical works that link dielectric relaxation in nematic liquid crystals to the dynamics of the director and dielectric heating, and illustrate how the dielectric memory effect features in electro-optics of these materials.

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Physical Properties: Magnetic Properties of Liquid Crystals

Cited by 14 publications

References 18 publications

Effect of Surface Anchoring on Creation of Defects in a Nematic Film. A Monte Carlo Simulation

Effect of Surface Anchoring on Creation of Defects in a Nematic Film. A Monte Carlo Simulation

Prenematic Self-Assembling of Mesogenic Molecules in Isotropic Liquid and Orientational Order in Nematic Phase

Dielectric relaxation and memory effects in nematic liquid crystals

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