The effect of molecular biaxiality on the bulk properties of some nematic liquid crystals

Bunning, John D.; Crellin, D. A.; Faber, T. E.

doi:10.1080/02678298608086488

Cited by 64 publications

(27 citation statements)

References 20 publications

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“…were used for the calculations: the elastic constants of the splay deformation K11 = 5.7 pN, the twist deformation K22 = 3.5 pN and the bend deformation K33 = 7.7 pN [36]; the extraordinary and ordinary refractive indices ne = 1.7002, no = 1.5294 (λ = 632.8 nm), respectively [37]; the thickness of LC layer d = 8.1 m, the helix pitch p = 21 m, the confinement ratio ρ = 0.4. Figure 3 shows the calculation data for the hybrid aligned cholesteric structure.…”

Section: Resultsmentioning

confidence: 99%

Orientational transition in the cholesteric layer induced by electrically controlled ionic modification of the surface anchoring

et al. 2016

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A reorientation of cholesteric liquid crystal with a large helix pitch induced by the electrically controlled ionic modification of the surface anchoring has been studied. In initial state, the cholesteric helix is untwisted completely owing to the normal surface anchoring specified by the cations adsorbed at the substrates. As a result, the homeotropic director configuration is observed within the cell. Under the action of dc electric field, one of the substrates becomes free from the layer of surface active cations, therefore, setting the planar surface anchoring. The latter, in turn, leads to the formation of the hybrid chiral structure. The threshold value and dynamic parameters have been estimated for this process as well as the range of control voltages, which do not allow the electrohydrodynamic instabilities. The twisted hybrid director configuration observed in the experiment has been analyzed by means of the simulation of polarization change of light propagating through the cholesteric layer with asymmetric (planar and homeotropic) surface anchoring on the cell substrates.

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Section: Resultsmentioning

confidence: 99%

Orientational transition in the cholesteric layer induced by electrically controlled ionic modification of the surface anchoring

et al. 2016

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“…Prototypical mesogenic units such as cyanobiphenyl species have ∆χ ≈ 10 −6 (in SI dimensionless volume units) [12,13]. ∆χ is very small for typical BCPs in the absence of mesogenic groups.…”

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Magnetic Alignment of Block Copolymer Microdomains by Intrinsic Chain Anisotropy

et al. 2015

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We examine the role of intrinsic chain susceptibility anisotropy in magnetic field directed selfassembly of a block copolymer using in situ X-ray scattering. Alignment of a lamellar mesophase is observed on cooling across the disorder-order transition with the resulting orientational order inversely proportional to the cooling rate. We discuss the origin of the susceptibility anisotropy, ∆χ, that drives alignment, and calculate its magnitude using coarse-grained molecular dynamics to sample conformations of surface-tethered chains, finding ∆χ ≈ 2 × 10 −8 . From field-dependent scattering data we estimate grains of ≈ 1.2 µm are present during alignment. These results demonstrate that intrinsic anisotropy is sufficient to support strong field-induced mesophase alignment and suggest a versatile strategy for field control of orientational order in block copolymers.

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“…16 The local field anisotropy in MBBA is small17 and doesn't change the dependence S( T ) in Equation (13). It is known from the precision measurements of the MBBA heat capacity's,'9 that To is 0.1" above the lower boundary g-) of the real two-phase region taken as T, in refractometric experiments.…”

Section: Longitudinal Susceptibility Of the Nematic Phase Of Mbbamentioning

confidence: 99%

Longitudinal Susceptibility of a Uniaxial Nematic

Aver'yanov

1991

Molecular Crystals and Liquid Crystals

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The relation between the longitudinal susceptibility x and the order parameter temperature dependence measured experimentally has been established for uniaxial nematics within the framework of the Landaude Gennes theory. The absolute values of x for the nematic phase, with MBBA as an example, have been obtained from experimental data for the first time and the critical behaviour of x has been studied.

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The effect of molecular biaxiality on the bulk properties of some nematic liquid crystals

Cited by 64 publications

References 20 publications

Orientational transition in the cholesteric layer induced by electrically controlled ionic modification of the surface anchoring

Orientational transition in the cholesteric layer induced by electrically controlled ionic modification of the surface anchoring

Magnetic Alignment of Block Copolymer Microdomains by Intrinsic Chain Anisotropy

Longitudinal Susceptibility of a Uniaxial Nematic

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