Showing papers by "Jan Jadżyn published in 2000"
TL;DR: In this paper, the results of measurements of the principal electric permittivities ∊ ∥*(T, ω and ∊⊥ *(T, ω) and the viscosity for 4-(trans-4-n-hexylcyclohexylhexyl)isothiocyanatobenzene (C6H13-CyHx-Bz-N=C=S, 6CHBT) were presented.
Abstract: This paper presents the results of measurements of the principal electric permittivities ∊ ∥*(T, ω and ∊⊥*(T, ω) and the viscosity for 4-(trans-4-n-hexylcyclohexyl)isothiocyanatobenzene (C6H13-CyHx-Bz-N=C=S, 6CHBT). In the nematic phase, the Miesowicz η2 viscosity coefficient was measured in a sample oriented due to the flow. On the basis of the temperature dependence of the static permittivities, using the Maier-Meier equations, the angle β between the dipole moment vector and the long axis of the 6CHBT molecule, the square of the molecular apparent dipole moment μ2 app 2 and the nematic order parameter S(T), were determined. From the temperature dependence of the viscosity and the relaxation time corresponding to the molecular rotation around the short axis, the strength of the nematic potential and the effective length of the 6CHBT molecule (in the isotropic phase) were estimated.
35 citations
TL;DR: In this paper, the authors measured the angle between the long molecular axis and the direction of the dipole moment of n-hexylcyanobiphenyl (C6H13−Ph-Ph-C N, 6CB) using the Maier-Meier equations.
Abstract: On the basis of the temperature dependence of the static principal permittivities, and , measured for the nematic phase of n-hexylcyanobiphenyl (C6H13–Ph–Ph–C N, 6CB), a value of the angle between the long molecular axis and the direction of the dipole moment of 6CB, as well as the order parameter S (T), were obtained by use of the Maier-Meier equations. From the dielectric relaxation and viscosity data, the contribution of the nematic potential to the molecular dynamics was estimated. In the isotropic phase the dielectric and viscosity data allow one, in the framework of the Debye model, to estimate the effective length of 6CB molecule.
9 citations
TL;DR: The results of the viscosity measurements performed for the isotropic phase of the homologous series of mesogenic 4-(trans-4-n-alkylcyclohexyl)isothiocyanatobenzenes (CnH2n+1−CyHxPhNCS, nCHBT) for n = 0 to n = 12 were presented in this article.
Abstract: This paper presents the results of the viscosity measurements performed for the isotropic phase of the homologous series of mesogenic 4-(trans-4-n-alkylcyclohexyl)isothiocyanatobenzenes (CnH2n+1−CyHxPhNCS, nCHBT) for n = 0 to n = 12.
6 citations
12 May 2000
TL;DR: In this paper, the results of measurements of the static and dynamic electric permittivities (epsilon) (parallel) (T,(omega) ) and (perpendicular)) of 4-(trans-4'-n-hexylcyclohexyl)isothiocyanato- benzene(C6H13-CyHx-Bz-NequalsCequalsS, 6-CHBT).
Abstract: The paper presents the results of measurements of the static and dynamic electric permittivities (epsilon) (parallel)*(T,(omega) ) and (epsilon) (perpendicular)*(T,(omega) ) of 4-(trans-4'-n-hexylcyclohexyl)isothiocyanato- benzene(C6H13-CyHx-Bz-NequalsCequalsS, 6-CHBT). On the basis of the temperature dependence of the static permittivities, using the Maier-Meier equations, the angle (beta) between the dipole moment vector and the long axis of 6-CHBT molecule, the square of the molecular apparent dipole moment (mu) 2app and the nematic order parameter S(T), were determined. The dielectric relaxation spectra were interpreted in the frame of the molecular model proposed recently.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
5 citations
TL;DR: In this article, the authors present results of shear viscosity measurements performed on nematogenic 4-(trans-4'-n-alkylcyclohexyl)isothiocyanatobenzenes (CnH 2n + 1-CyHx-Ph-N=C=S, /nCHBT) in the isotropic and nematic (n = 0 ÷ 12) phases.
Abstract: Abstract The paper presents results of shear viscosity measurements performed on nematogenic 4-(trans-4'-n-alkylcyclohexyl)isothiocyanatobenzenes (CnH 2n + 1-CyHx-Ph-N=C=S, /nCHBT) in the isotropic (n = 0 ÷ 12) and nematic (« = 4 ÷ 12) phases. The viscosity measured in the nematic phase is, due to the flow alignment phenomenon, close to the Migsowicz T? 2 viscosity coefficient. An odd-even effect in the n dependence of the viscosity-activation energy is observed both in the nematic and isotropic phases of nCHBT.
3 citations
12 May 2000
TL;DR: In this paper, the results of measurements of the dielectric relaxation of nematic 6-CHBT performed for different values ofthe angle between the directions of the macroscopic orientation of the sample (director n) and the probing electric field E.
Abstract: The paper presents the results of the measurements of the dielectric relaxation of nematic 6-CHBT performed for differentvalues ofthe angle between the directions of the macroscopic orientation of the sample (director n) and the probing electricfield E. Analysis ofthe evolution ofthe relaxation spectrum from 4(o) (E n) to i(o) (E I n) allowed one to explainthe inconsistency in the molecular interpretation ofthe spectra A model of the molecular dynamics in the oriented nematicsis proposed.Keywords: dielectric relaxation, neniatic, molecular dynamics 1. INTRODUCTION Studies of the dielectric relaxation in nematic liquid crystals are of a special interest and importance. The possibilityof control of the molecular orientation in the whole nematic sample by an electric I magnetic field or by an appropriatepreparation of the electrodes surface, gives an exceptional opportunity for studies of the molecular dynamics in correlation to the directions of the principal axes of the nematogenic molecule. One could expect that in such advantageous
3 citations
TL;DR: In this paper, a dielectric relaxation study was carried out for the nematic and isotropic phases of 4-(trans-4'-n-heptylcyclohexyl)isothiocyanatobenzene in the frequency range from 100 kHz to 1 GHz.
Abstract: Dielectric relaxation study was carried out for the nematic and isotropic phases of 4-(trans-4'-n-heptylcyclohexyl)isothiocyanatobenzene in the frequency range from 100 kHz to 1 GHz. In the nematic phase two relaxation processes were recorded for the electric permittivity component measured parallel to the molecular orientation (director n) and three relaxation processes — for the perpendicular permittivity component. The strength of the nematic potential and the nematic order parameter were estimated. PACS numbers: 64.70.Md, 77.84.Nh, 77.22.Gm
3 citations
12 May 2000
TL;DR: In this paper, the frequency dependence of the nonlinear dielectric increment for dilute benzene solutions of nematogenic molecules of different polarity was studied for the frequency range 1 MHz - 3 GHz.
Abstract: The frequency dependence of the nonlinear dielectric increment was studied for dilute benzene solutions of nematogenic molecules of different polarity: 4,4'-n- hexylcyanobiphenyl (C6H13-Ph-Ph-CequalsVN, 6CB, (mu) equals 4.8 D) and 4-(trans-4'-n-hexyl- cyclohexyl)isothiocyanatobenzene (C6H13-CyHx-Ph- NequalsCequalsS, 6CHBT, (mu) equals 3.5 D), at 25 degree(s)C. The increment was induced by the quasi-static electric field of high strength (107 V/m) and its relaxation was detected by the alternating field of low intensity (102 V/m) in the frequency range 1 MHz - 3 GHz. The results were discussed in the framework of Coffey's theory.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this article, the results of the dielectric relaxation study performed for the isotropic, nematic, and smectic A phases of 4-cyanophenyl 4-n-decyloxybenzoate (C 10 H21 O-Ph-COO-Ph −C≡N, CP1ODB) in the frequency range from 100 kHz to 100 MHz were presented.
Abstract: The paper presents the results of the dielectric relaxation study performed for the isotropic, nematic, and smectic A phases of 4-cyanophenyl 4'-n-decyloxybenzoate (C 10 H21 O—Ph—COO—Ph—C≡N, CP1ODB) in the frequency range from 100 kHz to 100 MHz. In the nematic and smectic A phases the permittivity was measured with the probing electric field E parallel to the macroscopic molecular orientation (the director n). The recorded dielectric spectra correspond to the rotation of CP1ODB molecules around the short axis and can be quite well described in the framework of the Debye model. It was found that the values of the activation energy for the molecular reorientations in the isotropic and smectic A phases of CP1ODB are quite close to each other, whereas in the nematic phase the energy is remarkably higher. PACS numbers: 64.70.Md, 77.84.Nh, 77.22.Gm