On the derivation of the nematic order parameter from the dielectric relaxation times

1999 ◽  
Vol 1 (11) ◽  
pp. 2787-2791 ◽  
Author(s):  
Stanisław Urban ◽  
Albert Würflinger ◽  
Bo Gestblom
Keyword(s):  
Dielectric Relaxation ◽  
Order Parameter ◽  
Relaxation Times ◽  
Nematic Order

Nematic order parameter as determined from dielectric relaxation data and other methods

2003 ◽  
Vol 5 (5) ◽  
pp. 924-928 ◽  
Author(s):  
Stanisław Urban ◽  
Bo Gestblom ◽  
Wojciech Kuczyński ◽  
Sebastian Pawlus ◽  
Albert Würflinger
Keyword(s):  
Dielectric Relaxation ◽  
Order Parameter ◽  
Relaxation Data ◽  
Nematic Order

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.

Relaxation processes of some simple aliphatic molecules in dilute solutions

1977 ◽  
Vol 55 (4) ◽  
pp. 297-301 ◽  
Author(s):  
M. P. Madan
Keyword(s):  
Carbon Tetrachloride ◽  
Dielectric Relaxation ◽  
Thermodynamic Parameters ◽  
Relaxation Times ◽  
Relaxation Processes ◽  
Dilute Solutions ◽  
Microwave Region ◽  
Nonpolar Solvents ◽  
Dielectric Data ◽  
Intramolecular Rotation

The dielectric relaxation processes of acetone, cyclohexanone, 4-methyl-2-pentanone, and 4-heptanone in dilute nonpolar solvents, n-heptane, cyclohexane, benzene, and carbon tetrachloride have been studied in the microwave region over a temperature range 10 to 60 °C. The relaxation times and the thermodynamic parameters for the activated states have been determined using the measured dielectric data. The results have been discussed in terms of dipole reorientation by molecular and intramolecular rotation and compared, wherever possible, with other similar studies on aliphatic molecules.

Dielectric Studies of 4-w-Hexyloxy-4’-Cyanobiphenyl (60CB) at Elevated Pressure

1999 ◽  
Vol 54 (6-7) ◽  
pp. 365-369 ◽  
Author(s):  
S. Urban ◽  
M. Smoluchowski
Keyword(s):  
Dielectric Permittivity ◽  
Order Parameter ◽  
Nematic Phase ◽  
Activation Volume ◽  
Activation Enthalpy ◽  
Ambient Pressure ◽  
Relaxation Times ◽  
Elevated Pressure ◽  
Dielectric Anisotropy ◽  
Dielectric Studies

Abstract The principal dielectric permittivity components in the nematic phase of 4-rc-hexyloxy-4’-cyanobiph-enyl (60CB) were measured as functions of temperature at ambient pressure and as functions of pres-sure up to 100 MPa at several constant temperatures. The dielectric anisotropy is analized in the frame of the Maier-Meier equations. The pressure dependence of the order parameter is deduced. Preliminary results for the activation volume and activation enthalpy from the pressure and temperature dependenc-es of the longitudinal relaxation times are obtained.

scholarly journals Dielectric Relaxation in Temperate Glaciers

1967 ◽  
Vol 6 (48) ◽  
pp. 897-909 ◽  
Author(s):  
P. W. F. Gribbon
Keyword(s):  
Dielectric Relaxation ◽  
Loss Factor ◽  
Relaxation Times ◽  
Frequency Range ◽  
Spreading Factor ◽  
Cold Surface ◽  
Relative Temperature ◽  
Low Frequencies ◽  
Glacial Ice ◽  
Impurity Ion

The dielectric relaxation ofnévéand glacial ice has been studied on two temperate glaciers in Greenland and France. Measurement of the capacitance and loss tangent in the audio-frequency range of thin parallel wires placed on the surface of a glacier gaveϵ′, the relative permittivity, andϵ″, the loss factor of thenévé. The relaxation time can be expressed in terms of the frequencyfmat the maximumϵ″ value of the Cole-Coleϵ″−ϵ′ diagram, and its variation with depth was derived from the Cole-Cole diagrams obtained for different wire separations.For wet 0°C. surface snow in Greenland,fm≈ 4 kHz. and decreased with the increase in density and form factor at greater depths, while for the low-density, cold surfacenévéin Francefm≈ 2 kHz. and increased with the increase in temperature at greater depths. All Cole-Cole diagrams showed both impurity-ion losses at low frequencies below 6 kHz., and a spreading factor of the distribution in relaxation times caused by the changes in the physical properties of the glacier with depth. Although the method could not measure temperatures absolutely, relative temperature differences and the position of the 0°C. isotherm were detected when a temperature gradient existed in a glacier.

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