The orientational behaviour of dichlorobenzenes in nematic liquid crystal solvents

1989 ◽  
Vol 67 (1) ◽  
pp. 54-59 ◽  
Author(s):  
C. T. Yim ◽  
D. F. R. Gilson
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Potential Energy ◽  
Electric Field ◽  
Electric Field Gradient ◽  
Short Range ◽  
Orientational Order ◽  
Energy Parameters ◽  
Average Electric Field ◽  
Shape And Size

The orientational order parameters of ortho-, meta-, and para-dichlorobenzene, dissolved in the nematic solvents EBBA and 1132, have been measured as functions of temperature and concentration, and used to determine the values of the potential energy parameters for each solute–solvent pair. These potentials have been interpreted in terms of a short-range contribution, which depends upon the shape and size of the solute molecule, plus a long-range term due to the interaction between the average electric field gradient from the solvent and the molecular quadrupole moment of the solute. Keywords: dichlorobenzenes, nematic solvents, liquid crystals, orientation, potential energy parameters.

The orientational ordering of solute molecules in nematic solvents: cyanobenzenes, bromobenzenes, and p-benzoquinone in EBBA and 1132

1990 ◽  
Vol 68 (6) ◽  
pp. 875-880 ◽  
Author(s):  
C. T. Yim ◽  
D. F. R. Gllson
Keyword(s):  
Liquid Crystals ◽  
Potential Energy ◽  
Electric Field Gradient ◽  
Short Range ◽  
Orientational Order ◽  
Short Range Interaction ◽  
Range Interaction ◽  
Average Electric Field ◽  
Orientational Ordering ◽  
Shape And Size

The orientational order parameters of benzonitrile and o-, m-, and p-dicyanobenzene, monobromo- and p-dibromobenzene, and p-benzoquinone, dissolved in two nematic solvents, 1132 and EBBA, have been measured as functions of temperature, and used to determine the potential energy parameters for each solute–solvent pair. These parameters have been correlated with a short-range interaction based upon a shape and size function of the solute molecule and a long-range contribution due to the interaction between the solute molecular quadrupole moment and the average electric field gradient. Keywords: nematic liquid crystals, orientational ordering of solutes.

Orientational order of 1,3-dichloro-2-ethenylbenzene in liquid-crystal solvents

1997 ◽  
Vol 75 (8) ◽  
pp. 1156-1161 ◽  
Author(s):  
J.C.T. Rendell ◽  
D.S. Zimmerman ◽  
A.J. van der Est ◽  
E.E. Burnell
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Moment Tensor ◽  
Orientational Order ◽  
Mean Field ◽  
Field Potential ◽  
Intermolecular Forces ◽  
Sample Tube ◽  
Average Electric Field ◽  
Nematic Solvent

The order parameter matrices of a molecule that has no symmetry, 1,3-dichloro-2-ethenylbenzene, dissolved in two different nematic liquid-crystal solvents are analyzed in terms of various models for the intermolecular mean-field potential. In a mixture of liquid crystals for which the interaction between the molecular quadrupole moment tensor and the average electric field gradient of the nematic solvent has been minimized, the orientational order is best described by models for the short-range anisotropic potential. The most successful potentials are written in terms of anisotropic interactions between the solute surface and the liquid-crystal mean field. This represents a strong test of such models because they simultaneously fit the five independent orientational parameters obtained from the same solute, thus removing the problems associated with comparing results among different solutes in either the same or a different sample tube. Keywords: liquid crystals, intermolecular forces, order parameters, anisotropic.

Line broadening in the electron resonance spectra of spin probes dissolved in anisotropic media: the effect of nuclear spin quantization

1977 ◽  
Vol 353 (1672) ◽  
pp. 87-102 ◽  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nuclear Spin ◽  
Dynamic Properties ◽  
Orientational Order ◽  
Anisotropic Media ◽  
Approximate Theory ◽  
Spin Probes ◽  
Line Broadening ◽  
Electron Resonance

The line broadening in the electron resonance spectra of monoradicals dissolved in anisotropic media, such as liquid crystals, provides a valuable probe of both the orientational order and the molecular dynamics. However, the fast-motion relaxation theory employed to extract this information from the linewidths assumes that the nuclear spin is quantized along the direction of the magnetic field. This approximation is only correct when the symmetry axis of a uniaxial liquid crystal is either parallel or perpendicular to the field. We have therefore removed this assumption and have developed a general theory of line broadening valid for all orientations of the liquid crystal. The theory is then used to evaluate the angular dependence of the linewidths and this is compared with the dependence predicted by the approximate theory, for two classes of nitroxide spin probes. These comparisons reveal that for steroidal spin probes the error, introduced by assuming the nuclear spin to be quantized along the field, is confined to the dynamic properties derived from the linewidths. In contrast, significant errors appear in both the dynamic and static properties obtained from an analysis of the linewidth variations for fatty acid spin probes based on the approximate theory. It would seem that the exact theory must be employed to obtain precise information from linewidth investigations of liquid crystals, except when the orientational order is extremely small.

Nano-Sized Fine Droplets of Liquid Crystals for Optical Application

1996 ◽  
Vol 457 ◽  
Author(s):  
Shiro Matsumoto ◽  
Marthe Houlbert ◽  
Takayoshi Hayashi ◽  
Ken-ichi Kubodera
Keyword(s):  
Liquid Crystal ◽  
Phase Separation ◽  
Liquid Crystals ◽  
Electric Field ◽  
Applied Voltage ◽  
Applied Electric Field ◽  
Uv Curing ◽  
Infrared Region ◽  
High Transparency ◽  
Power Change

ABSTRACTNano-sized fine droplets of liquid crystal (LC) were obtained by phase separation of nematic LC in UV curing polymer. The polymer composite had a high transparency in the infrared region. The fine droplets responded to an electric field causing a change in birefringence. Output power change was brought about by the generated retardation between two polarizations, parallel and perpendicular to the applied electric field. This differs from the composite containing much larger droplets, where output depends on the degree of scattering. The birefringence changed by 0.001 at the applied voltage of 7.5 V/μm.

Short range orientational order in nematic liquid crystals

Pramana ◽  
1977 ◽  
Vol 8 (1) ◽  
pp. 22-35 ◽  
Author(s):  
N V Madhusudana ◽  
K L Savithramma ◽  
S Chandrasekhar
Keyword(s):  
Liquid Crystals ◽  
Short Range ◽  
Nematic Liquid Crystals ◽  
Orientational Order

The breathers in nematic liquid crystals under applied electric field

2019 ◽  
Vol 33 (26) ◽  
pp. 1950319
Author(s):  
Yan Li ◽  
Xiaobo Lu ◽  
Chunfeng Hou
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Field ◽  
Nematic Liquid Crystal ◽  
Dynamic Equation ◽  
Applied Electric Field ◽  
Deflection Angle ◽  
Breather Solution ◽  
The Relationship ◽  
Sg Equation

In this paper, we study the twist of the nematic liquid crystal molecules under the applied electric field. The dynamic equation of the twisted molecules is derived. It is proved to be a kind of sine-Gordon (SG) equation. We obtain the breather solution of the equation and confirm that the deflection angles of the twisted molecules can distribute in the form of breathers. We give the relationship between the molecular deflection angle and the breather frequency, and discuss the effect of electric field on breather shape and breather frequency.

Electrically switchable reflection gratings in polymer dispersed liquid crystals

1999 ◽  
Vol 559 ◽  
Author(s):  
L. V. Natarajan ◽  
R. L. Sutherland ◽  
V. P. Tondiglia ◽  
S. Siwecki ◽  
R. Pogue ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Field ◽  
Low Voltage ◽  
Blue Shift ◽  
Maximum Efficiency ◽  
Acrylate Monomer ◽  
Polymer Dispersed ◽  
Reflection Gratings ◽  
Grating Formation

ABSTRACTElectrically switchable volume reflection holograms were written by inhomogeneous illumination of a prepolymer syrup containing a nematic liquid crystal and a multifunctional acrylate monomer. Switchable holograms are diffractive optics structures and the diffraction efficiency can be controlled by the application of an electric field. Reflection gratings with grating spacing varying between 0.16-0.27 µm were made during the phase separation of liquid crystals from the fast curing prepolymer syrup. The reflection efficiency of the holograms were electrically modulated with the applied field of ∼10-15V/µm. Real time study of the grating formation revealed that the maximum efficiency is reached in ∼15 seconds. The shrinkage of the host polymer during grating formation resulted in the blue shift of the reflection notch. The response time of the grating in an electric field is ∼50 µs. Low voltage scanning electron microscope studies showed the presence of discrete nematic droplet domains of sizes 30-60 nm in liquid crystal rich region.

scholarly journals Liquid crystals of carbon nanotubes and graphene

2013 ◽  
Vol 371 (1988) ◽  
pp. 20120499 ◽  
Author(s):  
Cécile Zakri ◽  
Christophe Blanc ◽  
Eric Grelet ◽  
Camilo Zamora-Ledezma ◽  
Nicolas Puech ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Order Parameter ◽  
Orientational Order ◽  
Point Of View ◽  
General Point ◽  
Conductivity Anisotropy ◽  
Conductive Films ◽  
Experimental Approaches ◽  
New Methodologies

Liquid crystal ordering is an opportunity to develop novel materials and applications with spontaneously aligned nanotubes or graphene particles. Nevertheless, achieving high orientational order parameter and large monodomains remains a challenge. In addition, our restricted knowledge of the structure of the currently available materials is a limitation for fundamental studies and future applications. This paper presents recent methodologies that have been developed to achieve large monodomains of nematic liquid crystals. These allow quantification and increase of their order parameters. Nematic ordering provides an efficient way to prepare conductive films that exhibit anisotropic properties. In particular, it is shown how the electrical conductivity anisotropy increases with the order parameter of the nematic liquid crystal. The order parameter can be tuned by controlling the length and entanglement of the nanotubes. In the second part of the paper, recent results on graphene liquid crystals are reported. The possibility to obtain water-based liquid crystals stabilized by surfactant molecules is demonstrated. Structural and thermodynamic characterizations provide indirect but statistical information on the dimensions of the graphene flakes. From a general point of view, this work presents experimental approaches to optimize the use of nanocarbons as liquid crystals and provides new methodologies for the still challenging characterization of such materials.

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