Low frequency dielectric spectroscopy of two room temperature chiral liquid crystal mixtures

2003 ◽  
Vol 76 (11) ◽  
pp. 945-958 ◽  
Author(s):  
M.B. Pandey ◽  
R. Dhar ◽  
K. Agrawal ◽  
R.P. Khare ◽  
R. Dabrowski
Keyword(s):  
Liquid Crystal ◽  
Dielectric Spectroscopy ◽  
Room Temperature ◽  
Low Frequency ◽  
Chiral Liquid Crystal

Spontaneous polarization, tilt angle, hysteresis and low-frequency relaxations in hydrogen bonded chiral liquid crystal dimer: M*SA:9OBA

2019 ◽  
Vol 551 (1) ◽  
pp. 178-196
Author(s):  
Mosalikanti Surekha ◽  
Attaluri Venkata Naga Ashok Kumar ◽  
Pallavajhula Venkata Chalapathy ◽  
Dakshina Murthy Potukuchi
Keyword(s):  
Liquid Crystal ◽  
Tilt Angle ◽  
Spontaneous Polarization ◽  
Low Frequency ◽  
Chiral Liquid Crystal ◽  
Hydrogen Bonded

Ionic Conductivity Induced Loss of Birefringence of Banana-Shaped Liquid Crystal

2010 ◽  
Vol 428-429 ◽  
pp. 220-223
Author(s):  
Yuan Ming Huang ◽  
Bao Gai Zhai
Keyword(s):  
Optical Properties ◽  
Liquid Crystal ◽  
Ionic Conductivity ◽  
Electric Field ◽  
Optical Microscopy ◽  
Dielectric Spectroscopy ◽  
Low Frequency ◽  
Triangular Waveform ◽  
Clearing Temperature

The effects of ionic conductivity on the electro-optical properties of a chiral banana-shaped liquid crystal 1,3-phenylene bis{4-[3-chloro-4-(3,7-dimethyloctyloxyl)] phenyliminomethyl} benzoate were investigated with the techniques of polarizing optical microscopy and dielectric spectroscopy. When the banana-shaped liquid crystal was experienced a low-frequency (1 Hz) triangular waveform electric field, its polarizing optical microscopic textures were first turned into gray and then into black at about 95oC, a few degrees lower than the clearing temperature of the banana-shaped liquid crystal. Detailed dielectric spectroscopic characterizations showed that ionic conductivity increased exponentially as the temperature increased from 72 to 110oC. Our results suggested that dominant ionic conductivity near its clearing temperature is responsible for the electric-field induced loss in the birefringence of the banana-shaped liquid crystal.

Relaxation, de Vries behavior, and layer contraction in chiral liquid crystal by dielectric spectroscopy

2018 ◽  
Vol 16 (3) ◽  
pp. 166-185 ◽  
Author(s):  
W.M. Zoghaib ◽  
A.K. George ◽  
C. Carboni ◽  
M. Surekha ◽  
A.V.N. Ashok Kumar ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Dielectric Spectroscopy ◽  
Chiral Liquid Crystal ◽  
De Vries

scholarly journals Dielectric properties of ternary composites of triblock polymer surfactant, liquid crystal and organic solvent

2014 ◽  
Vol 04 (03) ◽  
pp. 1450022 ◽  
Author(s):  
M. R. Fisch ◽  
Clinton Braganza ◽  
L. C. Chien ◽  
R. G. Petschek
Keyword(s):  
Liquid Crystal ◽  
Organic Solvent ◽  
Room Temperature ◽  
Low Frequency ◽  
Ternary Mixtures ◽  
Frequency Range ◽  
Getter Effect ◽  
Triblock Polymer ◽  
Polymer Surfactant ◽  
Triblock Polymers

Dielectric spectroscopy, at room temperature (20°C), is used to study the dielectric response of ternary mixtures of commercial nematic liquid crystal mixtures E7 and E33, an organic solvent N-Methyl-2-Pyrrolidone (NMP) and a triblock polymers in the frequency range from 0.01 Hz to 1 MHz. The results indicate a dielectric relaxation in the hectohertz region. Individually, both E7 and NMP have rather large low frequency conductivities; however, the low frequency (0.01–10 Hz) behavior of the mixtures has no such behavior. We attribute this behavior to an ion getter effect of the triblock polymer surfactant. Optimized ternary mixtures obtain a real dielectric constant near 230, and loss tangent less than 0.05 at frequencies near 10 mHz.

Attractive mode force microscopy of chiral liquid crystal surfaces

1992 ◽  
Vol 50 (1) ◽  
pp. 268-269
Author(s):  
B.D. Terris ◽  
R. J. Twieg ◽  
C. Nguyen ◽  
G. Sigaud ◽  
H. T. Nguyen
Keyword(s):  
Liquid Crystal ◽  
Crystal Surfaces ◽  
Free Surfaces ◽  
Control Range ◽  
Force Microscopy ◽  
Liquid Crystal Films ◽  
Chiral Liquid Crystal ◽  
Crystal Films ◽  
Electrostatic Charging ◽  
And Shifts

We have used a force microscope in the attractive, or noncontact, mode to image a variety of surfaces. In this mode, the microscope tip is oscillated near its resonant frequency and shifts in this frequency due to changes in the surface-tip force gradient are detected. We have used this technique in a variety of applications to polymers, including electrostatic charging, phase separation of ionomer surfaces, and crazing of glassy films.Most recently, we have applied the force microscope to imaging the free surfaces of chiral liquid crystal films. The compounds used (Table 1) have been chosen for their polymorphic variety of fluid mesophases, all of which exist within the temperature control range of our force microscope.

Dielectric Relaxation Studies of Silver Nanoparticles dispersed Liquid Crystal

2015 ◽  
Vol 8 (3) ◽  
pp. 2176-2188 ◽  
Author(s):  
Keisham Nanao Singh
Keyword(s):  
Activation Energy ◽  
Silver Nanoparticles ◽  
Liquid Crystal ◽  
Dielectric Relaxation ◽  
Relaxation Process ◽  
Relaxation Times ◽  
Low Frequency ◽  
Bulk Liquid ◽  
Molecular Rearrangement ◽  
Relaxation Studies

This article reports on the Dielectric Relaxation Studies of two Liquid Crystalline compounds - 7O.4 and 7O.6 - doped with dodecanethiol capped Silver Nanoparticles. The liquid crystal molecules are aligned homeotropically using CTAB. The low frequency relaxation process occurring above 1 MHz is fitted to Cole-Cole formula using the software Dielectric Spectra fit. The effect of the Silver Nanoparticles on the molecular dipole dynamics are discussed in terms of the fitted relaxation times, Cole-Cole distribution parameter and activation energy. The study indicate a local molecular rearrangement of the liquid crystal molecules without affecting the order of the bulk liquid crystal molecules but these local molecules surrounding the Silver Nanoparticles do not contribute to the relaxation process in the studied frequency range. The observed effect on activation energy suggests a change in interaction between the nanoparticles/liquid crystal molecules.

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