scholarly journals Chemical-Physical Characterization of a Binary Mixture of a Twist Bend Nematic Liquid Crystal with a Smectogen

Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1110
Author(s):  
Abir Aouini ◽  
Maurizio Nobili ◽  
Edouard Chauveau ◽  
Philippe Dieudonné-George ◽  
Gauthier Damême ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Liquid Crystalline ◽  
Smectic A ◽  
Liquid Crystalline Phases ◽  
Electro Optic ◽  
Optical Dielectric

Nematic twist-bend phases (NTB) are new types of nematic liquid crystalline phases with attractive properties for future electro-optic applications. However, most of these states are monotropic or are stable only in a narrow high temperature range. They are often destabilized under moderate cooling, and only a few single compounds have shown to give room temperature NTB phases. Mixtures of twist-bend nematic liquid crystals with simple nematogens have shown to strongly lower the nematic to NTB phase transition temperature. Here, we examined the behaviour of new types of mixtures with the dimeric liquid crystal [4′,4′-(heptane-1,7-diyl)bis(([1′,1″-biphenyl]4″-carbo-nitrile))] (CB7CB). This now well-known twist-bend nematic liquid crystal presents a nematic twist-bend phase below T ≈ 104 °C. Mixtures with other monomeric alkyl or alkoxy -biphenylcarbonitriles liquid crystals that display a smectic A (SmA) phase also strongly reduce this temperature. The most interesting smectogen is 4′-Octyl-4-biphenylcarbonitrile (8CB), for which a long-term metastable NTB phase is found at room and lower temperatures. This paper presents the complete phase diagram of the corresponding binary system and a detailed investigation of its thermal, optical, dielectric, and elastic properties.

Characterization of some mesogenic alkyl 1-thioglycosides

2002 ◽  
Vol 80 (8) ◽  
pp. 1162-1165 ◽  
Author(s):  
B Henrissat ◽  
G K Hamer ◽  
M G Taylor ◽  
R H Marchessault
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Solid State ◽  
Solid State Nmr ◽  
Liquid Crystalline ◽  
Liquid Crystal Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Liquid Crystalline Phases

A series of dodecyl 1-thio-β-D-glycosides has been synthesized and characterized (DSC, NMR, CP MAS, X-ray diffraction) as possible new marking materials with liquid-crystalline properties. These compounds undergo solid to liquid crystal phase transitions at various temperatures, which depend on the nature of the carbohydrate part of the structure. Their liquid-crystalline phases show extreme shear thinning behaviour.Key words: liquid crystal, powder X-ray diffraction, phase transition, thioglycoside, solid-state NMR, marking material

Morphology of elastic nematic liquid crystal membranes

Soft Matter ◽  
2017 ◽  
Vol 13 (32) ◽  
pp. 5366-5380 ◽  
Author(s):  
Pardis Rofouie ◽  
Damiano Pasini ◽  
Alejandro D. Rey
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Liquid Crystalline ◽  
Cell Membranes ◽  
Biological Materials ◽  
Crystalline Phases ◽  
Liquid Crystalline Phases

Liquid crystalline phases found in many biological materials, such as actin, DNA, cellulose, and collagen can be responsible for the deformation of cell membranes.

Liquid Crystalline System

2017 ◽  
pp. 190-216
Author(s):  
Nayan Ashok Gujarathi ◽  
Bhushan Rajendra Rane ◽  
Raj K. Keservani
Keyword(s):  
Drug Delivery ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Liquid Crystalline ◽  
Stable Phase ◽  
Science And Engineering ◽  
Liquid Crystalline Phases ◽  
Molecular Scale ◽  
Crystalline System ◽  
Liquid Crystalline System

Liquid crystalline system is a thermodynamically stable phase which is characterized by anisotropy. Liquid Crystals (LCs) are also termed as mesophase as they exhibit isotropic properties and liquid like behavior under some conditions (alter in temperature and concentration). Liquid crystals are influenced by number of parameters includes concentration, temperature, pH, and presence of salt. Liquid crystals are divided on the basis of shape of the molecules into two groups one is calmitic and other is discotic. A range of liquid crystalline phase (called mesophases) can be categorized by their sort of arrangement. The alignment of fragments in liquid crystalline phases is extensive on the molecular scale. Liquid crystal technology has a most important influence on several areas of pharmacy science and engineering, as well as device technology. As a novel type of drug delivery system, liquid crystals are explored and examined, definitely achieve mounting significance in industrial and scientific purposes.

Polarizing Optical Microscopic Characterization of Nematic Liquid Crystal Confined in Porous Silicon

2011 ◽  
Vol 181-182 ◽  
pp. 83-87
Author(s):  
Yuan Ming Huang ◽  
Qing Lan Ma ◽  
Bao Gai Zhai
Keyword(s):  
Experimental Study ◽  
Liquid Crystal ◽  
Porous Silicon ◽  
Optical Microscopy ◽  
Nematic Liquid Crystal ◽  
Experimental Investigations ◽  
Electro Optic ◽  
The Given

With polarizing optical microscopy we have investigated the electro-optic properties of a nematic liquid crystal 4-n-pentyl-4′-cyanobipheny confined in the microchannels of porous silicon. Experimental study shows clearly that the liquid crystal molecules tend to align parallel to the direction of the pore columns in porous silicon. Schlieren textures with S = +1 and +2 disclinations were recorded. Our experimental investigations show that uniaxial alignment, the planar radial and the escaped radial configurations exist around the given microchannels of porous silicon.

scholarly journals Synthesis and Characterization of Nonsymmetric Liquid Crystal Dimer Containing Biphenyl and Azobenzene Moiety

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
S. Sandy Subala ◽  
B. Syama Sundar ◽  
S. Sreehari Sastry
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystalline ◽  
Optical Microscope ◽  
Synthesis And Characterization ◽  
Spectroscopic Methods ◽  
Liquid Crystal Phase ◽  
Smectic A ◽  
Smectic C ◽  
Azobenzene Moiety

Calamitic liquid crystalline dimer containing azobenzene moiety and a decyloxy biphenyl linked by flexible spacers {4-[7-(4′-decyloxy-biphenyl-4-yloxy)-alkyloxy]-phenyl}-(4-decyl-phenyl)-diazene has been synthesized and characterized by spectroscopic methods. The transition temperatures and phase behaviours were studied by Differential Scanning Calorimeter (DSC) and Polarizing Optical Microscope (POM). The synthesized compounds exhibited enantiotropic liquid crystal phase with higher spacer display nematic and smectic C phases while lower spacer shows nematic and smectic A phases.

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.

Synthesis and Characterization of Bowl-Shaped Liquid Crystals with a Core of Calix[6]arene

2011 ◽  
Vol 396-398 ◽  
pp. 2202-2205
Author(s):  
Dan Shu Yao ◽  
Feng Li ◽  
Hao Jie Wang ◽  
Xiao Yun Li ◽  
Mei Tian ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Liquid Crystalline ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Cholesteric Phase ◽  
Chemical Structures ◽  
Liquid Crystalline Phases ◽  
Clearing Temperature ◽  
Mesomorphic Properties

A new kind of bowl-shaped liquid crystals were designed and synthesized by esterification. They used a calix[6]arene as central unit and ω- cholesteric alkyl diacid monoester as mesogenic arms. Their chemical structures were confirmed by FTIR and 1HNMR spectra, their mesomorphic properties and phase behavior were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-Ray Diffraction (XRD) measurements. The results showed that the kind of calix[6]arene bowl-shaped liquid crystals N1-N3 exhibited broad range liquid crystalline phases at moderate temperature, and they displayed cholesteric phase focal-conic texture in liquid crystal states. With increasing the flexibility of monomers M1-M3, the melting point and the clearing temperature decreased in the macromolecules.

High Pressure Studies of Liquid Crystalline Transitions

1983 ◽  
Vol 22 ◽  
Author(s):  
R. Shashidhar
Keyword(s):  
High Pressure ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Phase ◽  
Liquid Crystalline ◽  
Maximum Pressure ◽  
Multicritical Point ◽  
Smectic A ◽  
High Pressure Studies ◽  
Molecular Ordering

ABSTRACTSome of the important results emerging from our recent investigations on liquid crystals at high pressure are presented. In particular the following topics will be discussed: i) The relation between Pm, the maximum pressure of smectic stability, and the temperature range of the nematic phase in reentrant nematogenic compounds. ii) Piezothermal studies in the vicinity of the smectic A-nematic transition in 8 OCB. iii) The effect of molecular ordering on the pressure behaviour of the nematic-isotropic transition in reentrant nematic mixtures. iv) The first observation of a multicritical point in a single component liquid crystal.

New structure induced by elastic anisotropy in cylindrical nematic liquid crystal

2017 ◽  
Vol 13 (2) ◽  
pp. 4705-4717
Author(s):  
Zhang Qian ◽  
Zhou Xuan ◽  
Zhang Zhidong
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Elastic Anisotropy ◽  
Nematic Liquid Crystals ◽  
Gennes Theory

Basing on Landau–de Gennes theory, this study investigated the chiral configurations of nematic liquid crystals confined to cylindrical capillaries with homeotropic anchoring on the cylinder walls. When the elastic anisotropy (L2/L1) is large enough, a new structure results from the convergence of two opposite escape directions of the heterochiral twist and escape radial (TER) configurations. The new defect presents when L2/L1≥7 and disappears when L2/L1<7. The new structure possesses a heterochiral hyperbolic defect at the center and two homochiral radial defects on both sides. The two radial defects show different chiralities.

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