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1
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Determination of the Dielectric Anisotropy of Cholesteric Liquid Crystals

100%
Hoffmann J.
Acta Physica Polonica A
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2003
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vol. 103
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issue 1
41-46
EN
The method of determination of the main components of electric permittivity tensor for the cholesteric liquid crystals was proposed. The method was used to interpret the results obtained for pure 4-[(S,S)-2,3~epoxyhexyloxy]-phenyl-4-(decyloxy)-benzoate and the binary mixture of cyanobiphenyls.
2
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Extension of Maier-Meier Model on Cholesteric Liquid Crystals

100%
Hoffmann J.
Acta Physica Polonica A
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2004
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vol. 105
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issue 4
373-381
EN
Based on the Maier-Meier theory, a model is proposed in which the electric permittivity values of the cholesteric liquid crystals can be linked to their molecular parameters (μ - dipole moment,α - polarizability). To accomplish this project there were defined the transformation principles from the liquid crystal structure frame to the molecular frame, and a method for rendering the single molecule parameters (μ, α) into a set of averaged quantities of the macroscopic ensemble was offered. This model was used to calculate a dipole moment and polarizability for two liquid crystalline materials from electric permittivity measurements. The results are compared with the data obtained from MP3 calculations.
3
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Liquid Crystalline Polymorphism of Methyl and Ethyl trans-4-{[4'-(alkanoyloxy)phenyl]diazenyl}benzoates

63%
Niezgoda I., Galewski Z.
Acta Physica Polonica A
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2013
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vol. 124
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issue 6
926-932
EN
uthors present two new homologous series of liquid-crystalline compounds, methyl and ethyl 4-{[4-(alkanoyloxy)phenyl]diazenyl}benzoates, synthesis and investigation of their mesogenic properties. In the methyl series only nematic phase was detected and in the ethyl series nematic and smectic mesophases. Influence of the alkyl chain length on the phase transition temperatures and their entropic values are discussed and compared with literature data.
4
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Polymorphism and Initial Structure Modelling of a New Mesogen 9OSBch

63%
Kosyl M., Zając W., Ossowska-Chruściel M., Chruściel J.
Acta Physica Polonica A
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2013
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vol. 124
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issue 6
959-963
EN
We report the properties of a novel mesogen with high temperature cholesteric mesophase, which belongs to an unexplored as yet series of cholesteric esters. This compound is cholesteryl 4-(4-nonyloxybenzoylthio) benzoate (C_9H_{19}OC_6H_4COSC_6H_4COOch, where ch = cholesteryl), hereafter named 9OSBch. The chemical structure and purity of 9OSBch was established by ^1H NMR, ^{13}C NMR and FT-IR spectroscopy, and its mesomorphism was characterised by differential scanning calorimetry, polarizing optical microscopy, and transmitted light intensity. Differential scanning calorimetry measurements showed that substance is stable up to 270C and partially decomposes above this temperature. Observation under polarizing optical microscope revealed oily streak texture of cholesteric phase (Ch). The chemical structure of an isolated molecule was optimized by the density functional theory method. Energetically most favourable configuration is that of hockey stick geometry. At the same time this is the conformation best suited for the formation of highly ordered condensed phases.
5
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Dielectric and Conductivity Anisotropy in Liquid Crystalline Phases of Strongly Polar Thioesters

51%
Mikułko A., Fraś M., Marzec M., Wróbel S., Ossowska-Chruściel M., Chruściel J.
Acta Physica Polonica A
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2008
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vol. 113
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issue 4
1155-1160
EN
The main objective of this paper is to study dielectric properties of two compounds of acronyms 5OSCl and 6OSCl having strongly polar bond (C-Cl) at para position. Dielectric measurements were done in the frequency range from 40 Hz to 15 MHz. The dielectric spectra were measured for two principal alignments. For homeotropic alignment, the reorientation of molecule around the short molecular axis was observed. Both substances studied exhibit large positive dielectric anisotropy and the anisotropy of conductivity was obtained in smectic A as well as nematic phase.
6
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Molecular Dynamic of (4-(4'Octylobiphenyl)carboxylan) 4-(2-methylobuthyl) phenol Liquid Crystal Having Blue Phase Seen via the Dielectric Spectroscopy Method

51%
Otowski W., Lewińska G.
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vol. 125
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issue 5
1152-1158
EN
(4-(4'octylobiphenyl)carboxylan) 4-(2-methylobuthyl) phenol (CE8), the substance showing complex polymorphism, has been investigated using the dielectric spectroscopy method. This substance exhibited polymorphism during heating and cooling: a few smectic phases, a cholesteric phase, and a blue phase as well. Despite the fact that the substance polymorphism depends on the rate of heat flow existing of the blue phase has been confirmed by polarizing microscopic observations as well as dielectric spectroscopy investigations.
7
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Polymorphism Investigation of (4-(4'-Octylobiphenyl)carboxylane) 4-(2-Methylobuthyl) Phenol Liquid Crystal Having Blue Phase

51%
Lewińska G., Otowski W.
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issue 4
562-565
EN
(4-(4'-octylo-biphenyl)carbo-xylane) 4-(2-methylo-buthyl) phenol, the substance showing complex polymorphism, has been investigated using the calorimetric, microscopic and X-ray methods. This substance exhibited polymorphism during heating and cooling: a few smectic phases, a cholesteric phase and a blue phase as well. However, the substance polymorphism depends on the rate of heat flow. Existing of the blue phase has been confirmed by polarizing microscopic observations done at several temperature rates.
8
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Fast Stochastic Reorientations in Nematic PAA and PAP

51%
Podsiadły R., Mayer J., Janik J. A., Krawczyk J., Stanek T.
Acta Physica Polonica A
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1997
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vol. 91
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issue 3
513-518
EN
Incoherent quasielastic neutron scattering spectra were measured for nematic para-azoxyanisole (PAA) and para-azoxyphenetole (PAP) with the energy resolution of ca. 30 μ eV, at Dubna IBR-2 reactor. Data processing contained a careful background subtraction and the multiple scattering correction. The corrected spectra were subjected to a reorientational model fitting procedure. For PAA, a model of two convoluted reorientations - that of benzene rings coupled with the terminals and that of the whole molecule around the long molecular axis - gave a fairly good description of the quasielastic neutron scattering spectrum. For PAP, introducing a third motion - interconformational jumps in the ethoxy terminals - in addition to motions suggested for PAA, gave a good agreement with the measured quasielastic neutron scattering spectrum.
9
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Anomalous Dielectric Relaxation in Binary Mixtures of Mesogenic Solvent/Non-Mesogenic Solute

45%
Jadżyn J., Bauman D., Déjardin J., Ginovska M., Czechowski G.
Acta Physica Polonica A
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2005
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vol. 108
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issue 3
479-489
EN
Dielectric relaxation studies for mixtures of strongly polar and mesogenic n-heptylcyanobiphenyl with non-polar and non-mesogenic carbon tetrachloride (CCl_4) were performed. The absorption band broadening due to fractional diffusion was observed. A correlation between the non-mesogenic admixture concentration and the anomalous diffusion exponent was found.
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