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Wyświetlanie 1-15 z 23
Tytuł:
Spontaneous polarization and dielectric relaxation dynamics of two novel diastereomeric ferroelectric liquid crystals
Autorzy:
Huang, Lei-Ching
Fu, Chao-Ming
Powiązania:
https://bibliotekanauki.pl/articles/1075499.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Nh
77.22.Gm
Opis:
This study reports on the spontaneous polarization and molecular dynamics of two diastereomeric ferroelectric liquid crystals with a phenyl core ring but with different types of diastereomeric structures. The magnitudes of spontaneous polarization, measured via an Automated LC Property Tester, were similar for the two ferroelectric liquid crystals. The complex dielectric spectra, measured via an impedance analyzer, indicated the existence of the Goldstone mode in the ferroelectric (SmC*) phase for the two ferroelectric liquid crystals. Moreover, a novel ferrielectric-like (SmCγ*-like) phase was observed at certain temperatures. The complex dielectric spectra of the two ferroelectric liquid crystals were optimally analyzed by a theoretical model composed of the Debye model and the Cole-Cole model. The physical parameters such as relaxation frequency and dielectric strength were determined by a dielectric relaxation study, and the obtained parameters varied in accordance with phase transition sequence. The experimental results of dielectric spectra and spontaneous polarization are explained in the discussion of the mesomorphic properties related to the ferroelectric liquid crystal molecular structure.
Źródło:
Acta Physica Polonica A; 2016, 129, 1; 97-102
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ferroelectric Liquid Crystal for Use in a New Generation of LCDs
Autorzy:
Fitas, J.
Marzec, M.
Tykarska, M.
Wróbel, S.
Dąbrowski, R.
Powiązania:
https://bibliotekanauki.pl/articles/1399018.pdf
Data publikacji:
2013-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Nh
64.70.M-
Opis:
The key to improvements in liquid crystalline displays lies in the continuous synthesis and studies of new kinds of liquid crystalline substances. Among them, ferroelectric compounds are the subject of much attention, due to the potential progresses in switching time, colour depth, and other qualities of liquid crystal displays. In this paper we describe the research of the physical properties of 4-(2-methylbutoxy)phenyl 4-(octyloxy)-benzoate for purposes of its potential application in liquid crystal displays.
Źródło:
Acta Physica Polonica A; 2013, 124, 6; 954-958
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Statistical Theory of Biaxial Nematic and Cholesteric Phases
Autorzy:
Kapanowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1493357.pdf
Data publikacji:
2011-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.Cz
77.84.Nh
Opis:
A statistical theory of biaxial nematic and cholesteric phases is presented. It is derived in the thermodynamic limit at small density and small distortions. The considered phases are composed of short rigid biaxial or less symmetric molecules. The expressions for various macroscopic parameters involve the one-particle distribution function and the potential energy of two-body short-range interactions. The cholesteric phase is regarded as a distorted form of the nematic phase. Exemplary calculations are shown for several systems of molecules interacting via Corner-type potential based on the Lennard-Jones 12-6 functional dependence. The temperature dependence of the order parameters, the elastic constants, the phase twists, the dielectric susceptibilities, and the flexoelectric coefficients are obtained. The flow properties and defects in nematics are also discussed.
Źródło:
Acta Physica Polonica A; 2011, 120, 3; 351-367
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theory of the Dielectric Susceptibility of Liquid Crystals with Bent-Core Molecules
Autorzy:
Kapanowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1493613.pdf
Data publikacji:
2011-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.Cz
77.84.Nh
Opis:
Statistical theory of the dielectric susceptibility of polar liquid crystals is proposed. The molecules are calamitic or bent-core but the permanent dipole moment is perpendicular to the molecule long axis. The ordering of the phase is described by means of the mean-field theory based on the Maier-Saupe approach. The theory is used to calculate the temperature dependence of the order parameters and the susceptibilities. The phase diagram with four phases is obtained: isotropic, uniaxial nematic, uniaxial ferroelectric, and biaxial ferroelectric. Four critical points are predicted.
Źródło:
Acta Physica Polonica A; 2011, 120, 3; 473-479
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Studies of New Antiferroelectric Liquid Crystal Based on Quantum-Chemical Model
Autorzy:
Tomczyk, W.
Marzec, M.
Juszyńska, E.
Dąbrowski, R.
Ziobro, D.
Wróbel, S.
Massalska-Arodź, M.
Powiązania:
https://bibliotekanauki.pl/articles/1399016.pdf
Data publikacji:
2013-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Nh
64.70.M-
Opis:
Physical properties of new thermotropic antiferroelectric liquid crystal have been studied. Experiments were done by use of complementary methods such as differential scanning calorimetry, polarizing optical microscopy and X-ray powder diffractometry. Acquired data from X-ray powder diffractometry was examined under application of quantum chemical approach. It has been found that compound studied exhibits stable enantiotropic antiferroelectric SmC_{A}* phase in the wide temperature range while ferroelectric phase SmC* is very narrow.
Źródło:
Acta Physica Polonica A; 2013, 124, 6; 949-953
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Flexoelectric Effect in Biaxial Nematics
Autorzy:
Kapanowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1419785.pdf
Data publikacji:
2012-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.Cz
77.84.Nh
Opis:
The flexoelectric effect provides a linear coupling between electric polarization and orientational deformation in liquid crystals. It influences many electrooptical phenomena and it is used in some bistable nematic devices. A statistical theory of dipole flexoelectric polarization in biaxial nematic liquid crystals is used to calculate temperature dependence of order parameters, elastic constants, and flexoelectric coefficients. The splitting of the two Meyer flexoelectric coefficients and the appearance of new flexoelectric coefficients is obtained at the uniaxial-biaxial nematic transition. The ordering of the split flexoelectric coefficients corresponds to the ordering of the split elastic constants.
Źródło:
Acta Physica Polonica A; 2012, 122, 1; 146-151
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theory of the Dielectric Susceptibility of Liquid Crystals with Polar Nonuniaxial Molecules
Autorzy:
Kapanowski, A.
Wietecha, T.
Powiązania:
https://bibliotekanauki.pl/articles/2038179.pdf
Data publikacji:
2004-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.Cz
77.84.Nh
Opis:
Statistical theory of the dielectric susceptibility of polar liquid crystals is proposed. The molecules are not uniaxial but similar to cones. It is assumed that the permanent dipole moment of a molecule is parallel to the axis of the rotational symmetry. The ordering of the phase is described by means of the mean field theory based on the Maier-Saupe approach. The theory was used to calculate the temperature dependence of the order parameters and the susceptibilities. Predictions of the model for different sets of parameters are investigated.
Źródło:
Acta Physica Polonica A; 2004, 106, 1; 51-68
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric and Electrooptic Investigations of B Phases οf Banana-Shaped Thioesters
Autorzy:
Wierzejska-Adamowicz, M.
Ossowska-Chruściel, D.
Chruściel, J.
Douali, R.
Legrand, Ch.
Marzec, M.
Mikułko, A.
Sikorska, A.
Wróbel, S.
Powiązania:
https://bibliotekanauki.pl/articles/1538244.pdf
Data publikacji:
2010-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Nh
77.84.-s
78.20.Jq
Opis:
Electrooptic and dielectric measurements were done for B phases of two banana-shaped homologues 1,3-phenylene bis{4-[(4-nonylo-xy-benzoyl)sulfanyl]benzoate (9OSOR) and 1,3-phenylene bis{4-[(4-dodecylo-xy-benzoyl)sulfanyl]benzoate (12OSOR). Polarizing microscopy allowed to identify $B_{1}$ phase for 9OSOR and $B_{2}$ phase for 12OSOR on the basis of texture observation. Spontaneous polarization measurements were performed using reversal current method. The current response to applied triangular voltage shows that $B_{1}$ phase is a ferroelectric and $B_{2}$ phase - antiferroelectric one for which two well separated peaks were observed. Polarization for phase $B_{1}$ of 9OSOR is rather small and its temperature dependence is unusual for ferroelectric liquid crystals - it increases with temperature. Spontaneous polarization for $B_{2}$ phase of 12OSOR compound is of about 600 nC/$cm^{2}$. Dielectric spectra measured with bias field for $B_{2}$ phase of 12OSOR show two well separated relaxation processes. In the low frequency range the relaxation process is connected with fluctuations of ferroelectric domains. The relaxation process in the high frequency range appearing also without bias field is connected with molecular reorientation. The dielectric spectra measured for $B_{1}$ phase of 9OSOR with and without bias voltage showed only one dielectric relaxation process connected with molecular reorientation around the short axis.
Źródło:
Acta Physica Polonica A; 2010, 117, 4; 557-561
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Anomalous Dielectric Spectra of Ferro- and Ferrielectric Liquid Crystalline Phase in MHPNBC
Autorzy:
Dubois, F.
Douali, R.
Wawrzyniak, A.
Legrand, Ch.
Ropa, P.
Wróbel, S.
Dąbrowski, R.
Powiązania:
https://bibliotekanauki.pl/articles/1399013.pdf
Data publikacji:
2013-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.22.Gm
77.84.Nh
64.70.M
Opis:
MHPOBC analogue with long achiral alkyl chain has been investigated by dielectric spectroscopy studies in the wide temperature range. Low frequency dielectric spectroscopy revealed the existence of normal ferroelectric phase (in a narrow gap), two ferri- and three antiferroelectric phases in addition to paraelectric phase and alpha sub-phase. The compound studied shows exceptionally strong dependence of the dielectric permittivities on measuring electric field in the temperature range of ferro- and ferrielectric phases.
Źródło:
Acta Physica Polonica A; 2013, 124, 6; 937-939
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric Properties of Liquid Crystalline Isothiocyanato-tolane Derivatives with Fluorine Atom at Various Lateral Positions
Autorzy:
Czub, J.
Urban, S.
Dąbrowski, R.
Gestblom, B.
Powiązania:
https://bibliotekanauki.pl/articles/2043376.pdf
Data publikacji:
2005-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.70.Md
77.22.Gm
77.84.Nh
Opis:
Dielectric studies were performed for several isothiocyanato-tolane compounds having the F atom attached to the benzene rings at different lateral positions and the alkoxy or alkyl chain at the p-position. They form the nematic phase in broad temperature intervals. The static as well as dynamic properties of the compounds in the nematic and isotropic phases were studied. Tensor permittivity components: ε$\text{}_{ǁ}$, ε$\text{}_{⊥}$, Δε, as functions of temperature were measured. The complex dielectric permittivity, ε$\text{}^{*}$(f)=ε'(f)-iε''(f), was measured in the frequency range of 1 kHz - 3 GHz from which the relaxation times τ$\text{}_{ǁ}$ and τ$\text{}_{⊥}$ were calculated. The order parameter S(T) was determined from the dielectric data. It was found that the close vicinity of the F atom and the alkoxy group results in blocking of the internal rotation of the wing around the O-phenyl bond.
Źródło:
Acta Physica Polonica A; 2005, 107, 6; 947-958
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric Properties of Compounds Creating Dual-Frequency Nematic Liquid Crystals
Autorzy:
Mrukiewicz, M.
Perkowski, P.
Garbat, K.
Dąbrowski, R.
Parka, J.
Powiązania:
https://bibliotekanauki.pl/articles/1399014.pdf
Data publikacji:
2013-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.22.Gm
77.84.Nh
61.30.-v
Opis:
In this paper we report how dielectric spectroscopy can help in creating of dual-frequency nematic liquid crystals. Dual-frequency nematic liquid crystals is new class of liquid crystal materials. Such mixture is usually formed by a combination of many components (even more than 10), which can be split into two groups: molecules having large transverse dipole moment and molecules with a large longitudinal dipole moment. The behavior of a base (parent) mixture, functional admixtures and final dual-frequency nematic liquid crystals mixture is investigated by dielectric spectroscopy in wide frequency (100 Hz-10 MHz) and temperature ranges. This allows us to find out why the dual-frequency liquid crystal has an important feature: positive and negative dielectric anisotropy at different frequencies. We present parameters of molecular motions around short (S-mode) and long (L-mode) molecular axes observed in investigated materials and discuss how the creation of final dual-frequency nematic liquid crystals mixture can modify molecular relaxations.
Źródło:
Acta Physica Polonica A; 2013, 124, 6; 940-945
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Molecular Dynamics of 4-(trans-4-n-Heptylcyclohexyl)- Isothiocyanatobenzene Studied with Dielectric Relaxation Spectroscopy
Autorzy:
Bauman, D.
Czechowski, G.
Jadżyn, J.
Legrand, C.
Douali, R.
Powiązania:
https://bibliotekanauki.pl/articles/2014055.pdf
Data publikacji:
2000-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.70.Md
77.84.Nh
77.22.Gm
Opis:
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.
Źródło:
Acta Physica Polonica A; 2000, 98, 1-2; 71-81
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric Relaxation of 4-Cyanophenyl 4-n-Decyloxybenzoate in the Isotropic, Nematic, and Smectic A Phases
Autorzy:
Ginovska, M.
Czechowski, G.
Andonovski, A.
Jadżyn, J.
Powiązania:
https://bibliotekanauki.pl/articles/2014555.pdf
Data publikacji:
2000-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.70.Md
77.84.Nh
77.22.Gm
Opis:
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$\text{}_{10}$H$\text{}_{21}$O-Ph-COO-Ph-C≡ N, CP10DB) 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 CP10DB 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 CP10DB are quite close to each other, whereas in the nematic phase the energy is remarkably higher.
Źródło:
Acta Physica Polonica A; 2000, 98, 6; 715-720
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dynamics of Nematogenic Molecules with Transverse Component of Dipole Moment
Autorzy:
Douali, R.
Czechowski, G.
Legrand, Ch.
Jadżyn, J.
Powiązania:
https://bibliotekanauki.pl/articles/2037273.pdf
Data publikacji:
2004-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.70.Md
77.84.Nh
77.22.Gm
Opis:
The paper presents the results of studies of the dielectric relaxation of nematic 4'-butyloxy-3-fluoro- 4-isothiocyanatotolane, performed for different values of the angle between the probing electric field E and the macroscopic orientation of the sample (the director n) forced by the magnetic field B. Due to a relatively large transverse component of the dipole moment of 4'-butyloxy- 3-fluoro-4-isothiocyanatotolane, the studies allowed one to interpret consistently the dielectric relaxation spectra connected with the molecular rotation around the long axis.
Źródło:
Acta Physica Polonica A; 2004, 105, 4; 365-371
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Room Temperature Ferroelectric Mixture of Chiral and Achiral Thioesters
Autorzy:
Czerwiec, J.
Ossowska-Chruściel, M.
Chruściel, J.
Wróbel, S.
Powiązania:
https://bibliotekanauki.pl/articles/1538218.pdf
Data publikacji:
2010-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Nh
78.15.+e
64.70.M-
Opis:
Dielectric properties of the mixture of two thioester compounds: 4-8-alkoxy-benzoate-thio-carboxyl S-4-pentyl-phenyl (8OS5), (s)-4-(1-methyl-heptyloxy)biphenyl-4-thio-carboksyl 4-9-alkil-phenyl (MHOBS9) are presented. The chiral compound exhibits nematic (N*) and ferroelectric smectic C* phase (SmC*). The achiral compound shows N, SmA and monotropic SmC and SmB phases. the mixture of both compounds of 0.5 molar fraction shows SmC* in the wider temperature range than pure MHOBS9. The mixture was studied using frequency domain dielectric spectroscopy. Dielectric measurements for the SmC* phase of the mixture revealed Goldstone mode at higher frequencies and Maxwell-Wagner relaxation at low frequencies.
Źródło:
Acta Physica Polonica A; 2010, 117, 4; 549-552
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 23

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