Transient discharging processes in nematic liquid crystals

Naito, Hiroyoshi; Okuda, Masahiro; Sugimura, Akihiko

doi:10.1103/physreva.44.r3434

Cited by 63 publications

(31 citation statements)

References 9 publications

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“…In the pioneering papers the analysis was mainly focused on the re-normalization of the anchoring energy and flexoelectric coefficients due to the presence of the ions, and limited to considering the static situation [22][23][24][25][26][27][28][29][30][31][32][33]. Investigations of the influence of ions on the dynamical properties of nematic samples have been presented by several groups, mainly for practical applications [34][35][36][37][38][39][40][41][42][43][44][45][46][47]. In the relevant theoretical analysis, the characteristic times are the diffusion time and the drift time [48].…”

Section: Introductionmentioning

confidence: 99%

Adsorption–desorption phenomenon and the kinetic equation at interfaces in liquid crystalline systems

Evangelista

Barbero

2006

Liquid Crystals

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The adsorption-desorption phenomenon in a sample having the shape of a slab is investigated by using a particular form for the kinetic equation at the limiting surfaces. A closed solution for the time evolution of the ion density in a nematic liquid crystal sample submitted to an external field is obtained in the limit in which the effective field coincides with the external field. In this framework it is shown that the intrinsic time connected with the presence of the electric field is proportional to the drift time. The constant of proportionality is of the order of the ratio between the thermal agitation energy and the electrostatic energy. In a similar manner, the time evolution of the bulk and surface densities, in the case of neutral particles, is also determined in a closed form by means of a simple expression. A microscopic model giving rise to a kinetic equation, similar to the one used in the analysis, is presented. We propose a statistical interpretation of the adsorption-desorption phenomenon in the framework of Maxwell-Boltzmann statistics, in which the relationship between the phenomenological parameters, entering into the kinetic equation at the boundary surfaces, with the microscopic model is derived. The analysis is suitable for the description of the adsorption phenomena of neutral particles (dyes) as well as charged particles (ions) in nematic liquid crystals.

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Section: Introductionmentioning

confidence: 99%

Adsorption–desorption phenomenon and the kinetic equation at interfaces in liquid crystalline systems

Evangelista

Barbero

2006

Liquid Crystals

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“…The transport of the ions under the action of an electric field was characterized by their mobil− ity and diffusion coefficients. It was assumed that the mobil− ity of the positive ions was much smaller than that of the negative ions [8,9]. The values used in calculations corre− sponded to typical results of mobility measurements in vari− ous liquid crystals and reflected typical anisotropy of mobility [10,11], m || .…”

Section: Geometry and Parametersmentioning

confidence: 99%

Numerical investigation of influence of ionic space charge and flexoelectric polarization on measurements of elastic constants in nematic liquid crystals

Buczkowska

Derfel

Konowalski

2009

Opto-Electronics Review

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Deformations of nematic layers caused by magnetic field allow determination of the elastic constants of liquid crystal. In this paper, we simulated numerically the deformations of planar and homeotropic nematic layers. The flexoelectric properties of the nematic and presence of ions were taken into account. Our aim was to show the influence of flexoelectricity on the results of the real measurement of the elastic constants k33 and k11. In these simulations, we calculated the optical phase difference ΔΦ between the ordinary and extraordinary rays of light passing through the layer placed between crossed polarizers as a function of the magnetic field induction B. One of the elastic constants can be calculated from the magnetic field threshold for deformation. The ratio k33/k11 can be found by means of fitting theoretical ΔΦ(B) dependence to the experimental results. The calculations reveal that the flexoelectric properties influence the deformations induced by the external magnetic field. In the case of highly pure samples, this may lead to false results of measurement of the elastic constants ratio k33/k11. This influence can be reduced if the nematic material contains ions of sufficiently high concentration. These results show that the flexoelectric properties may play an important role, especially in well purified samples.

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“…for z = ±1 2, where g = Wd k 11 . The boundary conditions for the potential are V(-1/2) = 0 and V U LC ( ) 1 2 = .…”

Section: Basic Equationsmentioning

confidence: 99%

“…The transport of the ions in the liquid crystal was characterised by their mobility and diffusion coefficients. It was assumed that the mobility of the positive ions was much smaller than that of the negative ions [11]. Their values used in calculations corresponded to typical results of mobility measurements in various liquid crystals and reflected typical anisotropy of mobility m || -= 1.5×10 -9 m 2 /Vs, m^-= 1×10 -9 m 2 /Vs, m || + = 1.5×10 -10 m 2 /Vs, and m^+ = 1×10 -10 m 2 /Vs [12,13].…”

Section: Geometry and Parametersmentioning

confidence: 99%

One dimensional model of dye-doped nematic layer for holography

Derfel

Buczkowska

Parka

2006

Opto-Electronics Review

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The layer of electrically conducting nematic liquid crystal doped with photosensitive dye and confined between polyimide coated electrodes can serve as a diffraction grating. In this paper, the deformations of the nematic director field induced in such a system by external voltage were studied numerically by means of one-dimensional model. The dissociation and recombination of ions were taken into account according to weak electrolyte model. The director orientation in the deformed layers and the distributions of the electric field and of the ion concentrations were calculated for blocking and for conducting electrodes. The effective extraordinary refractive index was also determined as a function of average ion concentration.

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Transient discharging processes in nematic liquid crystals

Cited by 63 publications

References 9 publications

Adsorption–desorption phenomenon and the kinetic equation at interfaces in liquid crystalline systems

Adsorption–desorption phenomenon and the kinetic equation at interfaces in liquid crystalline systems

Numerical investigation of influence of ionic space charge and flexoelectric polarization on measurements of elastic constants in nematic liquid crystals

One dimensional model of dye-doped nematic layer for holography

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