Showing papers by "Jan Jadżyn published in 1999"
TL;DR: In this paper, the authors presented the results of studies of the dielectric relaxation of 6CHBT obtained for different values of the angle between the directions of the macroscopic orientation of the sample (director n) and the probing electric field E. A model of the molecular dynamics in the oriented nematics is proposed.
Abstract: This paper presents the results of studies of the dielectric relaxation of nematic 6CHBT obtained for different values of the angle between the directions of the macroscopic orientation of the sample (director n) and the probing electric field E. Analysis of the evolution of the relaxation spectrum from e*‖(ω) (E‖n) to e*⊥(ω) (E⊥n)allows one to explain the hitherto existing inconsistency in the molecular interpretation of the spectra. A model of the molecular dynamics in the oriented nematics is proposed.
40 citations
TL;DR: In this article, the temperature dependence of the principal static permittivities of nematics epsilon (T) and Epsilon(T) was analyzed using the Maier-Meier equations, and the following quantities were obtained: (i) the angle between the dipole moment vector and the long axis of the mesogenic molecules, (ii) the square of the apparent molecular dipole moments, and (iii) the nematic order parameter S(T).
Abstract: This paper shows that on the basis of the temperature dependence of the principal static permittivities of nematics epsilon (T) and epsilon (T), using the Maier-Meier equations, the following quantities can be obtained: (i) the angle between the dipole moment vector and the long axis of the mesogenic molecules, (ii) the square of the apparent molecular dipole moment mu2app(T) and (iii) the nematic order parameter S(T).
30 citations
TL;DR: In this article, the nonlinear dielectric relaxation in dilute solutions of strongly polar molecules (4,4′-nhexylcyanobiphenyl) in nonpolar medium (benzene) has been investigated.
22 citations
TL;DR: In this paper, the frequency dependence of the nonlinear dielectric increment for dilute solutions of 10-TPEB molecules (C 10 H 21 −∅−∅-CH 2 −CH 2 -∅ −NCS) in benzene have been performed at different temperatures.
21 citations
TL;DR: In this paper, two samples of ferronematics based on 8CB liquid crystal with different volume fractions of magnetic particles were prepared and the influence of magnetic field on the electric Fredericksz transition was studied using magneto-dielectric measurements.
20 citations
TL;DR: In this article, a method for evaluation of the fraction of the molecules which are not affected by the polymer surface anchoring forces in the nematic droplets is proposed, based on the analysis of dielectric absorption studies for polymer dispersed liquid crystal (PDLC) samples of different nematic contents.
Abstract: Dielectric absorption studies for polymer dispersed liquid crystal (PDLC) samples of different nematic (4-hexyl-4'-cyanobiphenyl, 6CB) contents (20, 30, and 40 wt%) have been carried out in the frequency range from 10kHz to 10MHz. A method for evaluation of the fraction of the molecules which are not affected by the polymer surface anchoring forces in the nematic droplets is proposed.
17 citations
TL;DR: In this paper, a new class of stable, low melting nematics with a negative dielectric anisotropy is described. And the basic physical properties of 2-chloro-4-heptylphenyl 4-pentylbicyclo-[2, 2,2,2] octane-1-carboxylate (7CP5BOC) are presented.
Abstract: Synthesis of a new class of stable, low melting nematics with a negative dielectric anisotropy is described. The basic physical properties of 2-chloro-4-heptylphenyl 4-pentylbicy-clo-[2,2,2]octane-1-carboxylate (7CP5BOC) are presented.
9 citations
TL;DR: In this paper, the results of the studies of the Debye function and the nonlinear dipolar relaxation (described by the Coffey function) have been presented for diluted solution of 4,4′-n-hexylcyanobiphenyl (6-CB) in benzene at 25°C.
5 citations
14 Dec 1999
TL;DR: In this paper, the authors measured static electric permittivity and dielectric relaxation in isotropic and nematic phase of 6-OCB and 8-OCB using the Maier-Meier equations.
Abstract: Static electric permittivity and dielectric relaxation have been measured in isotropic and nematic phase of 6-OCB and 8- OCB. On the basis of the temperature dependence of the principal static permittivities of nematics, (epsilon) (parallel)(T) and (epsilon) (perpendicular)(T), using the Maier-Meier equations, the following quantities have been obtained: i) the angle between the dipole moment vector and the long axis of mesogenic molecules, ii) the molecule apparent dipole moment square (mu) 2app(T) and iii) the nematic order parameter S(T). From the temperature dependence of the dielectric relaxation time, the activation energy for the molecular rotation around the short axis has been calculated and, taking into account the viscosity data, the effective dimensions of the nematogen molecules have been evaluated.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
2 citations
14 Dec 1999
TL;DR: In this paper, the nonlinear dielectric effect has been measured with a weak alternating field superimposed on a strong quasi-static bias field of the amplitude of 1.1 X 107 V/m.
Abstract: Studies of the nonlinear dipolar relaxation in the frequency range from 1 MHz to 3 GHz have been carried out for diluted solutions of 4,4'-n-hexylcyanobiphenyl and 4-(trans-4'-n- hexylcyclohexyl)isothiocyanatobenzene in benzene at 25 degrees C. The nonlinear dielectric effect has been measured with a weak alternating field superimposed on a strong quasi-static bias field of the amplitude of 1.1 X 107 V/m. The nonlinear relaxation spectrum has been interpreted in terms of the theory proposed by Coffey et al.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
1 citations
TL;DR: In this article, the frequency dependence of the nonlinear dielectric increment was studied for benzene solutions of the nematogenic molecule 4-(trans-4′-n-hexylcyclohexyl)isothiocyanatobenzene (C6H13CyHx-PhN=C=S, 6CHBT) at 25°C.
Abstract: The frequency dependence of the nonlinear dielectric increment was studied for benzene solutions of the nematogenic molecule 4-(trans-4′-n-hexylcyclohexyl)isothiocyanatobenzene (C6H13CyHx-PhN=C=S, 6CHBT) at 25°C. The increment was induced by a quasi-static electric field of high strength (10 V/m), and its relaxation was detected by an alternating field of low strength (10 V/m) in the frequency range 1 MHz–3 GHz. The results are discussed in the framework of Coffey’s theory.
Journal Article•
14 Dec 1999
TL;DR: In this paper, dielectric relaxation studies for n-hexylcyanobiphenyl in pure state and dispersed in a polymer matrix have been performed, and a method for evaluation of the fraction of the 6-CB molecules which are not affected by the polymer surface anchoring forces in the nematic droplets has been presented.
Abstract: Dielectric relaxation studies for n-hexylcyanobiphenyl in pure state and dispersed in polymer matrix, have been performed. Polymer dispersed liquid crystal (PDLC) films have been prepared with different 6-CB contents. The measurements have been carried out in the frequency range 10 kHz divided by 100 MHz for pure 6-CB and 10 kHz divided by 10 MHz for PDLC films. A method for evaluation of the fraction of the 6-CB molecules which are not affected by the polymer surface anchoring forces in the nematic droplets, has been presented.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.