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    Wyświetlanie 1-23 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
    Tytuł:
    Electro-Optical Properties of Liquid Crystals Composite with Zinc Oxide Nanoparticles
    Autorzy:
    Eskalen, H.
    Özğan, Ş.
    Alver, Ü.
    Kerlı, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398924.pdf
    Data publikacji:
    2015-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.20.Jq
    77.84.Nh
    78.20.Fm
    Opis:
    In this study, zinc oxide (ZnO) nanoparticles were synthesized by spray pyrolysis method. The properties of ZnO nanoparticles are determined by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and UV-vis spectroscopy. Nematic liquid crystal mixture E7 was doped with 1, 2, and 4% ZnO. We investigate electrical and optical parameters of pure and doped nematic liquid crystal mixture E7. The experiments related to voltage dependence and light transmittance of the pure and doped E7 were carried out. The values of threshold voltage, total phase retardation and birefringence are examined. The results show that doping zinc oxide nanoparticles into liquid crystal mixture E7 decreases threshold voltage significantly.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 3; 756-760
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dielectric Properties of Ferroelectric Liquid Crystals with Diversified Molecular Structure
    Autorzy:
    Czerwiec, J.
    Dąbrowski, R.
    Żurowska, M.
    Ziobro, D.
    Wróbel, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1538235.pdf
    Data publikacji:
    2010-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    77.84.Nh
    78.15.+e
    64.70.M-
    Opis:
    Mesomorphic, thermodynamic, electro-optic and dielectric properties of three homologues of fluorosubstituted esters are described. Full chemical names of these compounds are as follows: (S)-(+)-4-(1-metyl-hepty-loksy)benzoate-(6-penta-fluoro-propano-ynloxyhex-1-oxy)-biphenyl-4-yl (in short 2F6BBiOC8), (S)-(+)-4-(1-metyl-hepty-loksy)benzoate-(6-nona-fluoro-pentano-yloxyhex-1-oxy)-biphenyl-4-yl (in short 4F6BBiOC8), (S)-(+)-4-(1-metyl-hepty-loksy)benzoate-(6-trideca-fluoro-heptano-yloxyhex-1-oxy)-biphenyl-4-yl (in short 6F6BBiOC8). The compounds exhibit ferroelectric smectic C* phase between crystalline and isotropic phase. Only one compound (6F6BBiOC8) shows antiferroelectric phase $(SmC_{A}^\ast)$ observed by dielectric spectroscopy, but the range of this phase is narrow of about 2°. All three compounds exhibit in the SmC* phase Goldstone mode and Maxwell-Wagner relaxation hidden in the conductivity contribution at low frequencies, whereas in the $SmC_{A}^\ast$ phase two anti-ferroelectric modes (AFM1) and (AFM2) contribute to the dielectric spectrum. The compounds were studied using differential scanning calorimetric, frequency domain dielectric spectroscopy, and reversal currents method to determine spontaneous polarization.
    Źródło:
    Acta Physica Polonica A; 2010, 117, 4; 553-556
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Polymorphism of Chiral Thioester Studied by Dielectric Spectroscopy
    Autorzy:
    Wawrzyniak, A.
    Chruściel, J.
    Douali, R.
    Dubois, F.
    Leblond, J.
    Legrand, Ch.
    Ossowska-Chruściel, D.
    Marzec, M.
    Ropa, P.
    Czerwiec, J.
    Wróbel, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399012.pdf
    Data publikacji:
    2013-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    77.84.Nh
    64.70.M-
    77.22.Gm
    77.22.Ej
    Opis:
    (S)-(+)-4'-[(4-(1-methylheptyloxycarbonylphenyl) thiocarbonylphenyl]-decyloxybenzoate (in short 10.OPOSMH) was studied by complementary methods. The substance shows rich polymorphism. In addition to ferroelectric and antiferroelectric smectic C* phases it possesses three ferrielectric sub-phases. Phase transitions between the phases were revealed by differential scanning calorimetry and static dielectric permittivity measurements. The aim of this paper was to study phase transitions and differences in dielectric spectra shown by different phases. Collective and molecular dynamics of all phases shown by 10.OPOSMH will be discussed in terms of theoretical models. Dielectric spectra of antiferroelectric phase show two characteristic dielectric relaxation modes: one connected with the molecular process (reorientation around the short axis) and the other originating from fluctuations of antiferroelectric order parameters.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 6; 933-936
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dielectric, Viscous, and Elastic Properties of Mesogenic 4-n-Hexyloxy-4-Cyanobiphenyl
    Autorzy:
    Czechowski, G.
    Jadżyn, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2027368.pdf
    Data publikacji:
    2001-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    64.70.Md
    77.84.Nh
    77.22.Gm
    66.20.+d
    Opis:
    The paper presents the results of measurements of the static and dynamic electric permittivity, the shear viscosity, and the splay and bend elastic constants for 4-n-hexyloxy-4' -cyanobiphenyl (C$\text{}_{6}$H$\text{}_{13}$O-Ph-Ph-C≡N). On the basis of the static values of the nematic principal permittivities, ε$\text{}_{ǁ}$ (T) and $\varepsilon_{\bot}(T)$, the angle between the dipole moment vector and the long axis of 4-n-hexyloxy-4'-cyanobiphenyl molecule, the apparent dipole moment and the nematic order parameter were determined. From the temperature dependences of the dielectric relaxation time (corresponding to the molecular rotation around the short axis) and the shear viscosity, the strength of the nematic potential and the effective length of 4-n-hexyloxy-4'-cyanobiphenyl molecule (in isotropic phase) were estimated. The K$\text{}_{11}$ and K$\text{}_{33}$ elastic constants were determined from the voltage dependence of the capacitance of the planar nematic cell with the method proposed by Gruler et al. and Uchida et al.
    Źródło:
    Acta Physica Polonica A; 2001, 99, 5; 579-591
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dynamics and Phase Transitions of 4-Bromobenzylidene-4'-pentyloxyaniline and 4-Bromobenzylidene-4'-hexyloxyaniline as Studied by Dielectric Spectroscopy
    Autorzy:
    Osiecka, N.
    Massalska-Arodź, M.
    Galewski, Z.
    Chłędowska, K.
    Wróbel, S.
    Morito, T.
    Yamamura, Y.
    Saito, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399008.pdf
    Data publikacji:
    2013-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    77.84.Nh
    64.70.pp
    64.70.M-
    33.15.Bh
    Opis:
    Significant differences in phase sequence and dynamics between 4-bromobenzylidene-4'-pentyloxyaniline (5BBA) and -bromobenzylidene-4'-heksyloxyaniline (6BBA) substances were detected by broadband dielectric spectroscopy. In the smectic A (6BBA), the smectic B (found in both substances) and the smectic E (5BBA) phases the relaxation was ascribed to reorientations of the molecules around the short axes. Slow dynamics detected in the smectic E and in two crystalline phases of 5BBA was ascribed to conformational changes of molecular chains. Coexistence of Cr(I) and Cr(II) conformationally disordered crystal (CONDIS) phases was observed and vitrification of Cr(II) was identified with help of polarizing microscopy.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 6; 913-916
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Magnetic-Field Induced Isotropic-Nematic Phase Transition in PDLC Doped with Magnetic Nanoparticles
    Autorzy:
    Mitróová, Z.
    Tomašovičová, N.
    Timko, M.
    Koneracká, M.
    Tomčo, L.
    Jadżyn, J.
    Palewski,, T.
    Kopčanský, P.
    Kovalchuk, O.
    Powiązania:
    https://bibliotekanauki.pl/articles/1429068.pdf
    Data publikacji:
    2012-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.30.Gd
    75.30.Hx
    75.75.Fk
    77.84.Nh
    Opis:
    The paper presents a study of the polymer dispersed liquid crystals that consist of liquid crystal 4-trans-4'-n-hexyl-cyclohexyl-isothiocyanatobenzene (6CHBT) microdroplets dispersed in polyvinyl alcohol and doped with various kinds of magnetic particles. As magnetic nanoparticles there were used single walled carbon nanotubes and magnetite labeled single walled carbon nanotubes. The volume concentration of the particles was 2 × $10^{-3}$. Magnetic properties were investigated by a SQUID magnetometer. The higher saturation magnetization has been achieved in sample polymer dispersed liquid crystal doped with magnetite labeled single walled carbon nanotubes. The phase transition temperature from isotropic to nematic phase at the external magnetic field 0 T and 12 T was monitored by precise capacitance measurements in the capacitance cell filled with prepared sample. The significant shift of the phase transition temperature (0.2°C) at the external magnetic field 12 T has been observed in sample polymer dispersed liquid crystal doped with magnetite labeled single walled carbon nanotubes.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 5-6; 1299-1301
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Comparison of Different Liquid Crystal Materials under Planar and Homeotropic Boundary Conditions in Capillaries
    Autorzy:
    Chychłowski, M.
    Ertman, S.
    Nowinowski-Kruszelnicki, E.
    Dąbrowski, R.
    Woliński, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/1493035.pdf
    Data publikacji:
    2011-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    42.70.Df
    61.30.Jf
    77.84.Nh
    42.79.Kr
    Opis:
    We present a thermally-induced liquid crystal orientation method by applying an extra orienting layer onto an inner capillary surface that can induce either planar or homeotropic liquid crystal boundary conditions. Experimental evidence of boundary-induced orientation in two types of liquid crystal (nematic, chiral nematic) in a capillary are shown.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 4; 582-584
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Calculation of Optical Parameters of Liquid Crystals
    Autorzy:
    Kumar, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1814025.pdf
    Data publikacji:
    2007-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.20.-e
    78.20.Ci
    78.20.Fm
    77.84.Nh
    Opis:
    Validation of a modified four-parameter model describing temperature effect on liquid crystal refractive indices is being reported in the present article. This model is based upon the Vuks equation. Experimental data of ordinary and extraordinary refractive indices for two liquid crystal samples MLC-9200-000 and MLC-6608 are used to validate the above-mentioned theoretical model. Using these experimental data, birefringence, order parameter, normalized polarizabilities, and the temperature gradient of refractive indices are determined. Two methods: directly using birefringence measurements and using Haller's extrapolation procedure are adopted for the determination of order parameter. Both approches of order parameter calculation are compared. The temperature dependences of all these parameters are discussed. A close agreement between theory and experiment is obtained.
    Źródło:
    Acta Physica Polonica A; 2007, 112, 6; 1213-1221
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-23 z 23

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