Formation of a smectic A phase from a strongly deformed planar nematic liquid crystal CBOOA

Hinov, H. P.

doi:10.1051/jphys:01981004202030700

Cited by 33 publications

(10 citation statements)

References 53 publications

(41 reference statements)

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“…Figure a shows the variation in the free energy Δ F = ρ for a TFCD in microchannels of different depth h , as calculated using eq with K = 5 × 10 − 11 N, K̅ = 0, ξ = 3 × 10 − 9 m, Δσ subs = −1.2 × 10 −3 N/m, , and σ ⊥ air = 20 × 10 − 3 N/m . Note that K is assumed to be about 5 times larger than that for general alkyl-terminated SmA materials such as 8CB, , to reflect the fact that the fluorinated LC molecules are more rigid than other LCs due to the fluorinated moiety in the tail group. , This assumption is not critical, as smaller values of K produce similar results, especially if the surface tension anisotropy (Δσ subs ) is also adjusted.…”

Section: Resultsmentioning

confidence: 99%

Confined Self-Assembly of Toric Focal Conic Domains (The Effects of Confined Geometry on the Feature Size of Toric Focal Conic Domains)

et al. 2009

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A smectic liquid crystal (LC) containing a rigid biphenyl group and semifluorinated chains exhibits a high density of toric focal conic domains (TFCDs) arranged in an ordered array when confined within a microchannel. The formation of the TFCDs is strongly influenced by the width (W) and depth (h) of the confined microchannels, most importantly, by the channel depth. We studied a broad variety of microchannels, with varying width in the range of 3-200 mum and depth in the range of 2-10 mum. The radius of the TFCDs increases with increases in the width until the saturated radius is achieved, which is determined by the depth of the channel. We used the elastic-anchoring model of TFCD formation to explain the experimental observations. The model allows one to trace the dependence of the TFCD radius on the channel depth h, to explain why the TFCDs do not form in channels that are too shallow or too narrow.

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Section: Resultsmentioning

confidence: 99%

Confined Self-Assembly of Toric Focal Conic Domains (The Effects of Confined Geometry on the Feature Size of Toric Focal Conic Domains)

et al. 2009

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“…The LC cell was described elsewhere [4]. It consists of two glass plates with a large area (several cmz) covered with a semitransparent conductive layer and separated by mylar spacers with a thickness between 10 and 100pm.…”

Section: Preparation Of the Lc Samples And Experimental Set-upmentioning

confidence: 99%

“…The mechanical stability was achieved by means of four screws (see Fig. 1 in [4]). The liquid crystal was introduced in the empty cell in its isotropic phase.…”

Section: Preparation Of the Lc Samples And Experimental Set-upmentioning

confidence: 99%

DC voltage-controlled pulsations of a homotropic nematic layer with a free-sliping liquid crystal–polar liquid boundary

Hinov

1987

Phys. Stat. Sol. (a)

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DC voltage‐controlled infrasound quasiperiodic pulsations of a homeotropic nematic layer with a free‐sliping boundary liquid crystal‐polar liquid in a conventional sandwich cell are discovered. Such pulsations appear at a well‐defined threshold voltage which is around 3.5 to 4.5 V. Their period depends crucially on the nature of the polar liquid and for the liquid crystal water sample it is several seconds while for the liquid crystal–glycerin sample it is several tens of seconds. It seems that the pulsations are connected with the formation and saturation of the electric double layers around the interfaces liquid crystal‐polar liquid. The appearance of the instability probably by the mechanism of Rayleigh–Taylor evidently discharges or destroys the electric double layers which again are formed accompanied by the reappearance of the instability. This novel electrooptic effect can be applied to the display technique.

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“…When such structures are cooled to the temperature of nematic-to-smectic phase transition, the orientation distribution function changes. Due to the incompatibility of director distortions with the layer structure of the smectic phase, complex textures are formed at the transition to the smectic phase, wherein director discontinuities are concentrated in disclination lines and domain boundaries. , Such textures have been experimentally observed using polarized optical microscopy. − However, direct experimental measurements of the orientation distribution function of distorted smectic samples have not yet been performed, and the techniques suited for this task are not sufficiently well developed. In this work, we aim to apply the spin probe technique to this task and perform experimental determination of the orientation distribution functions of liquid crystals in cells with an arbitrary director geometry.…”

Section: Introductionmentioning

confidence: 99%

Orientation Distribution of Molecules in a Smectic Liquid Crystal with a Distorted Director Geometry

Bogdanov

Vorobiev

2022

J. Phys. Chem. B

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Quantitative determination of the molecular orientation distribution function in samples of liquid crystals with a complex director geometry was performed using the numerical simulation of electron paramagnetic resonance (EPR) spectra of the spin probes in a liquid-crystalline medium. To achieve the quantitative agreement of experimental and simulated EPR spectra, the hierarchy of the orientation order was explicitly taken into account, namely, the local ordering of liquid crystal molecules by the mean-field potential of surrounding molecules, and the partial disordering of local directors within the sample. The samples under study are planar and twist LC cells with liquid crystal 8CB cooled from the nematic into the smectic A phase in the magnetic field. The presence of the magnetic field perpendicular to the cell director leads to distortion of the orientation of the liquid crystal in the cell. The spin probe technique was successfully employed for the reliable measurement of orientation distribution functions of the low nonorthorhombic symmetry. Orientation order parameters up to 12th rank were measured, including nonaxial and nonorthorhombic order parameters. It is shown that the presence of several contradicting aligning forces leads to the tilt of the preferential director toward the direction, which is a compromise between the orienting forces.

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Formation of a smectic A phase from a strongly deformed planar nematic liquid crystal CBOOA

Abstract: Résumé. 2014

Cited by 33 publications

References 53 publications

Confined Self-Assembly of Toric Focal Conic Domains (The Effects of Confined Geometry on the Feature Size of Toric Focal Conic Domains)

Confined Self-Assembly of Toric Focal Conic Domains (The Effects of Confined Geometry on the Feature Size of Toric Focal Conic Domains)

DC voltage-controlled pulsations of a homotropic nematic layer with a free-sliping liquid crystal–polar liquid boundary

Orientation Distribution of Molecules in a Smectic Liquid Crystal with a Distorted Director Geometry

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