scholarly journals Optical Kossel Lines and Fluorescence in Photonic Liquid Crystals

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 541
Author(s):  
Vladimir A. Belyakov
Keyword(s):  
Experimental Data ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Absorption ◽  
Fluorescence Polarization ◽  
Direct Connection ◽  
X Ray ◽  
Optical Analog ◽  
Theoretical Results ◽  
Observation Results

We propose a general analytical way to describe the fluorescence peculiarities in photonic liquid crystals (revealing themselves as an optical analog of the X-ray Kossel lines in conventional crystals) based at the localized optical edge modes existing in perfect photonic liquid crystal layers. The proposed approach allows us to predict theoretically the properties of optical Kossel lines in photonic liquid crystal (fluorescence polarization, spectral and angular fluorescence distribution, influence of the light absorption in liquid crystal, and, in particular, existing the optical Borrmann effect if the absorption in liquid crystal is locally anisotropic). Comparison of the theoretical results and the known experimental data shows that the theory reproduces sufficiently well the observation results on the fluorescence in photonic liquid crystals. For confirming a direct connection of the optical Kossel lines to the localized optical edge modes in perfect photonic liquid crystal, we propose the application of time-delayed techniques in studying the optical Kossel lines.

New liquid crystal formation induced by nanoscale phase separation composed of bent-core liquid crystal and rod-like cholesteric liquid crystal mixtures

Soft Matter ◽  
2021 ◽  
Author(s):  
Yoichi Takanishi
Keyword(s):  
Liquid Crystal ◽  
Phase Separation ◽  
Liquid Crystals ◽  
Small Angle ◽  
Cholesteric Liquid Crystal ◽  
Crystal Formation ◽  
Nano Structure ◽  
X Ray ◽  
Nanoscale Phase Separation ◽  
X Ray Scattering

Herein, the local nano-structure in mixtures of cholesteric liquid crystals and a bent-core molecule was analyzed via the small-angle X-ray scattering.

X-RAY INVESTIGATION ON TEMPERATURE DEPENDENCE OF THE TILT ANGLE IN FERROELECTRIC LIQUID CRYSTALS

1989 ◽  
Vol 03 (16) ◽  
pp. 1247-1250 ◽  
Author(s):  
XIANG ZHANG ◽  
ZHENGMIN SUN ◽  
DUAN FENG ◽  
GUOZHEN LI
Keyword(s):  
Experimental Data ◽  
Liquid Crystals ◽  
Critical Exponent ◽  
Temperature Dependence ◽  
Tilt Angle ◽  
Diffraction Measurement ◽  
X Ray Diffraction ◽  
Ferroelectric Liquid Crystals ◽  
X Ray

The temperature dependence of the molecular tilt angle in a series of ferroelectric liquid crystals is deduced from X-ray diffraction measurement. The critical exponent β has been estimated from the experimental data. The non-classical value of β for the compounds lies in the range 0.36–0.41.

Rectilinear low-frequency shear of homogeneously aligned nematic liquid crystals

1993 ◽  
Vol 441 (1913) ◽  
pp. 559-573 ◽  
Keyword(s):  
Thin Film ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Theoretical Analysis ◽  
Low Frequency ◽  
The Other ◽  
Critical Amplitude ◽  
Linear Shear ◽  
Theoretical Results ◽  
Good Agreement

A thin film of nematic liquid crystal (ZLI 1085) is sandwiched between two horizontally mounted glass blocks, whose faces have been treated to align the molecules of the liquid parallel to the plane of the blocks. By moving one block relative to the other in its own plane, the liquid crystal is subjected to an oscillatory linear shear. Above a certain frequency-dependent amplitude, mechanical Williams domains of alternating bright and dark stripes are observed perpendicular to the direction of shear. A theoretical analysis of this phenomenon is carried out to provide predictions for both the thickness of the stripes and the critical amplitude as a function of frequency. Good agreement is found between the experimental and theoretical results.

scholarly journals Fatty Acid-Derived Ionic Liquid Lubricant. Protic Ionic Liquid Crystals as Protic Ionic Liquid Additives

Coatings ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 710 ◽  
Author(s):  
María-Dolores Avilés ◽  
Ramón Pamies ◽  
José Sanes ◽  
Francisco-José Carrión ◽  
María-Dolores Bermúdez
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Liquid Crystal ◽  
Fatty Acid ◽  
Liquid Crystals ◽  
Water Evaporation ◽  
Protic Ionic Liquid ◽  
X Ray ◽  
Sliding Surfaces ◽  
Ionic Liquid Crystals

Fatty acids are natural products which have been studied as green lubricants. Ionic liquids are considered efficient friction reducing and wear preventing lubricants and lubricant additives. Fatty acid-derived ionic liquids have shown potential as neat lubricant and additives. Protic ionic liquid crystals (PILCs) are protic ionic liquids (PILs) where cations and anions form ordered mesophases that show liquid crystalline behavior. The adsorption of carboxylate units on sliding surfaces can enhance the lubricant performance. Ionic liquid crystal lubricants with longer alkyl chains can separate sliding surfaces more efficiently. However, they are usually solid at room temperature and, when used as additives in water, transitions to high friction coefficients and wear rates, with tribocorrosion processes occur when water evaporation takes place at the interface. In order to avoid these inconveniences, in the present work, a protic ammonium palmitate (DPA) ionic liquid crystal has been added in 1 wt.% proportion to a short chain citrate ionic liquid (DCi) with the same protic ammonium cation. A spin coated layer of (DCi + DPA) was deposited on AISI316L steel surface before the sliding test against sapphire ball. Synergy between DCi PIL and DPA PILC additive reduces friction coefficient and wear rate, without tribocorrosion processes, as shown by scanning electron microscopy (SEM)/energy dispersive X-ray microanalysis (EDX) and X-ray photoelectron spectroscopy (XPS) results.

INFLUENCE OF THE FLOW ON THE ORIENTATION INDUCED BY A SOLID SUBSTRATE ON A NEMATIC LIQUID CRYSTAL

1992 ◽  
Vol 06 (03n04) ◽  
pp. 437-448 ◽  
Author(s):  
G. BARBERO ◽  
A. N. CHUVYROV ◽  
A. P. KREKHOV
Keyword(s):  
Experimental Data ◽  
Liquid Crystal ◽  
Simple Model ◽  
Nematic Liquid Crystal ◽  
Solid Substrate ◽  
Sample Thickness ◽  
Filling Process ◽  
Total Surface Energy ◽  
Surface Anchoring ◽  
Theoretical Results

The influence of the flow on the orientation induced by a solid substrate on a nematic liquid crystal is experimentally and theoretically analyzed. Our experimental data show that a nematic cell filled by capillarity presents a birefringence dependent on the sample thickness. This fact suggests that the symmetry of the problem is broken by the filling process. A simple model is presented in order to explain the experimental observations. According to this model, a surface anchoring contribution to the total surface energy, of the same order of the usual one appearing in the Rapini-Papoular expression, is connected to the flow. The agreement between the experimental data and the theoretical results is fairly good.

Liquid Crystals in Ternary Polyoxyethylene Trisiloxane Surfactant - Silicone Oil - H2O System

1996 ◽  
Vol 425 ◽  
Author(s):  
X. Li ◽  
R. M. Hill ◽  
L. E. Scriven ◽  
H. T. Davis
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Small Angle ◽  
Silicone Oil ◽  
Head Group ◽  
X Ray ◽  
X Ray Scattering ◽  
Crystal Phases ◽  
Liquid Crystal Phases ◽  
Ray Scattering

AbstractPolyethylene trisiloxane surfactants M(D′En)M (n=6, 8, 10, 12) self assemble into sheet-like structure and form various lyotropic cubic, hexagonal and lamellar liquid crystal phases in ternary trisiloxane surfactant - silicone oil - water systems. Small angle X-ray scattering (SAXS) was used to identify and characterize the liquid crystal phases. Cyclic octamethylcyclotetrasiloxane (D4), decamethyl-cyclopentasiloxane(D5) and short linear decamethyltetrasiloxane (MD2M) silicone oils facilitate the formation of liquid crystals. The structures in liquid crystals (LC) progress from zero curvature lamellar liquid crystals to higher curvature cubic liquid crystals with increasing the surfactant hydrophilic head group size. The effects of surfactant and oil concentration on the lamellar bilayer thickness and molecular packing were studied with small angle X-ray scattering.

Zustandsdiagramme und röntgenographische Untersuchungen einiger induzierter smektischer Mischphasen / Phase Diagrams and X -R ay Studies of the Induced Smectic Phases of Liquid Crystal Mixtures

1978 ◽  
Vol 33 (9) ◽  
pp. 1077-1084 ◽  
Author(s):  
B. Engelen ◽  
F. Schneider
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Phase Diagrams ◽  
Layer Thickness ◽  
Polar Liquid ◽  
X Ray ◽  
Polar Components ◽  
Smectic Phases ◽  
Induced Smectic Phases

Phase diagrams of mixtures of terminal polar and terminal non-polar liquid crystals that exhibit smectic phases with very large ranges of stability are presented. X-ray studies show that the in­duced phases are of type SA, SB or SE. The determination of the layer thickness shows that the induced smectic phases are composed of monolayers, whereas the terminal polar components are composed of bilayers. A model for the formation of the induced smectic phases is proposed.

Discotic liquid crystals of transition metal complexes 57: X-ray diffraction halo jumps originated from sudden free rotation of substituent groups to induce mesomorphism

2020 ◽  
Vol 24 (04) ◽  
pp. 563-576
Author(s):  
Takahiro Nishiguchi ◽  
Kouki Sugiyama ◽  
Hiromu Nakamura ◽  
Mikio Yasutake ◽  
Kazuchika Ohta
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Crystalline Phase ◽  
Alkyl Chain ◽  
Copper Phthalocyanine ◽  
Free Rotation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Alkyl Chains ◽  
Long Alkyl Chain

We have synthesized a novel series of four flying-seed-like liquid crystals (1Ph-PhO)4PcM [5-M: M = Co (5-Co), Ni (5-Ni), Cu (5-Cu) and Zn (5-Zn)] which are based on a phthalocyanine core having peripheral bulky groups without long alkyl chains, in order to clarify the precise mechanism inducing their mesomorphism. For comparison, we have also synthesized a long alkyl-chain-substituted liquid crystal ([Formula: see text]C[Formula: see text]OPhO)8PcCu (7o) having the same phthalocyanine core with long alkyl chains in the periphery. Each of the derivatives 5-M and 7o showed a hexagonal ordered columnar (Colho) mesophase. Very interestingly, the halo positions in the X-ray diffraction patterns for the Colho mesophases of the flying-seed-like liquid crystals 5-M and the long alkyl-chain-substituted liquid crystal 7o were quite differently given at 5.7–6.2 Å and 4.6–4.7 Å, respectively. The halo positions of the representative derivatives 5-Cu and 7o having the same copper phthalocyanine (PcCu) core were finely measured at various temperatures by using the temperature-variable small angle X-ray diffraction technique. As the result, the derivatives 5-Cu and 7o showed sudden jumps of halo position from 5.5 to 5.7 Å and from 4.2 to 4.6 Å, respectively, at the phase transition from the crystalline phase to the liquid crystalline phase (Colho). This means that the volume changes ([Formula: see text]V) corresponding to these halo jumps originate from two different kinds of mechanisms by sudden free rotation of the bulky substituents and by sudden melting of the long alkyl chains. Thus, in this work we have unambiguously clarified these two different mechanisms inducing mesomorphism.

Spatially Resolved Characterization of the Electroclinic Effect in Chiral Smectic a Liquid Crystals

1996 ◽  
Vol 425 ◽  
Author(s):  
J. R. Lindle ◽  
S. R. Flom ◽  
F. J. Bartoli ◽  
A. T. Harter ◽  
R. E. Geer ◽  
...  
Keyword(s):  
Optical Properties ◽  
Angular Distribution ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Tilt Angle ◽  
X Ray ◽  
Smectic A ◽  
Spatially Resolved ◽  
Smectic A Liquid Crystals

AbstractThe electro-optical properties of an electroclinic liquid crystal have been investigated using a spatially resolved technique which measures the birefringence, optical tilt angle and extinction within adjacent stripe domains. A comparison of these results with the data obtained from standard optical and X-ray measurements suggests the presence of substripes or an angular distribution of molecular directors within the stripe domains.

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