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Wyświetlanie 1-15 z 21
Tytuł:
Physical Studies of Cyclohexane Derivatives
Autorzy:
Murthy, Y. N.
Ramanaiah, M. V.
Murthy, V. R.
Powiązania:
https://bibliotekanauki.pl/articles/2012947.pdf
Data publikacji:
2000-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
Opis:
Mean molecular polarizabilities, polarizability anisotropies and order parameters of two homologous series of cyclohexane derivatives namely trans-4-alkyl cyclohexyl 4'-cyanophenyl ester and trans-4-alkyl cyclohexyl 4'-n-pentyloxy phenyl ester are evaluated using molecular vibration approach. The variation of polarizability and polarizability anisotropy with a number of carbon atoms in the alkyl chain is studied. In addition, the dependence of order parameter on temperature is reported and discussed.
Źródło:
Acta Physica Polonica A; 2000, 97, 2; 315-322
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Molecular Vibration Approach to Polarizabilities of Methyl Cinnamate Liquid Crystal Compounds
Autorzy:
Murthy, Y. N.
Murthy, V. R.
Ranga Reddy, R. N. V.
Powiązania:
https://bibliotekanauki.pl/articles/1964211.pdf
Data publikacji:
1997-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
Opis:
A new theoretical method of evaluating polarizabilities of liquid crystals is presented and applied to the liquid crystalline compounds, namely n-alkyl-p-(4-ethoxy benzylidene amino)-α-methyl cinnamates, which exhibit smectic A and nematic phases. In the present method, vibrational frequencies are used to evaluate force constants, mean amplitude of vibration and hence bond polarizabilities. From mean polarizabilities, polarizability anisotropies and mean diamagnetic susceptibilities are also estimated. A close agreement is found between the values estimated from the present molecular vibration method and the reported data, which confirms the applicability of this method to the liquid crystals exhibiting smectic A and nematic phases. In addition, the variation of the order parameter with temperature is also studied.
Źródło:
Acta Physica Polonica A; 1997, 91, 6; 1069-1079
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Induced Smectic A Phase through Intermolecular Hydrogen Bonding: Part XVIII: Influence of p-n-Alkyl Benzoic Acids on Thermal and Phase Behavior οf Hydrogen-Bonded Liquid Crystals
Autorzy:
Vijayalakshmi, K.
Sreehari Sastry, S.
Powiązania:
https://bibliotekanauki.pl/articles/1808111.pdf
Data publikacji:
2009-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
61.30.Cz
Opis:
A novel series of intermolecular hydrogen bonded liquid crystals was synthesized with the mesogens of p-n-alkyl benzoic acids (nBA where n =5 to 10) and p-(p'-octyloxy benzylidene)-cyano aniline (OBCA) moieties. The thermal and phase behaviors of these mesogens (nBA:OBCA) are studied by thermal polarizing optical microscopy and differential scanning calorimetry techniques. Induced smectic A phase with focal conic fan texture is observed in all the synthesized compounds. Moreover, the nematic phase present in all the pure p-n-alkyl benzoic acids (nBA where n =6 to 10) is quenched in all the hydrogen bonded compounds (nBA:OBCA) and smectic A phase is induced. But, in the compound 5BA:OBCA the nematic phase is also present along with the induced smectic A phase. The structural elucidation pertaining to the formation and stabilization of intermolecular hydrogen bonding is carried out by a detailed IR spectral investigation.
Źródło:
Acta Physica Polonica A; 2009, 115, 3; 690-693
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Physical Studies of Binary Mesophase Mixtures Containing N-(p-Propoxy Benzylidene)-p-Pentylaniline
Autorzy:
Ranga Reddy, R. N. V.
Reddy, K. C.
Murthy, V. R.
Powiązania:
https://bibliotekanauki.pl/articles/1931627.pdf
Data publikacji:
1994-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
35.20.My
61.30.-v
Opis:
The applicability of the modified Lippincott δ-function model method is tested for binary mesophase mixtures. Using this method, the polarizabilities, polarizability anisotropies and order parameters of binary mesophase mixtures containing N-(p-propoxy-benzylidene)-p-pentylaniline are evaluated and compared with the reported values. A close agreement is observed between the estimated values and reported values.
Źródło:
Acta Physica Polonica A; 1994, 86, 3; 385-391
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Refractive Indices, Order Parameter and Optical Transmittance Studies of a Nematic Liquid Crystal Mixture
Autorzy:
Singh, A. K.
Manohar, R.
Shukla, J. P.
Biradar, A. M.
Powiązania:
https://bibliotekanauki.pl/articles/2047089.pdf
Data publikacji:
2006-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
42.70.Df
Opis:
Measurements of ordinary refractive index, birefringence, density, and order parameter were made on a technologically important nematogen and the data obtained for its nematic and isotropic phase were reported. A modified wedge method was used for the measurement of the birefringence (δ n). The nematic-isotropic phase transition temperature matches very well as is exhibited from the value of refractive indices and densities obtained using different techniques. The optical anisotropy and density data were used to determine the order parameter and principal polarizability of the nematic mixture using the Vuks approach and their temperature dependence was discussed. The macroscopic order parameter was obtained and compared with microscopic order parameter. These two values agree very well.
Źródło:
Acta Physica Polonica A; 2006, 110, 4; 485-493
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical Study of the Effect of Light on Nematic to Isotropic Phase Transition
Autorzy:
Suresha, B.
Radhakrishna, M.
Govind, A.
Powiązania:
https://bibliotekanauki.pl/articles/1493611.pdf
Data publikacji:
2011-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
64.70.M-
Opis:
Optical response of liquid crystals is very important from the point of view of applications of liquid crystals in display and data storage devices. Experiments have shown that UV rays incident on nematic liquid crystals doped with photoactive azo compounds lower the nematic isotropic transition temperature $(T_{NI})$. This is attributed to the transformation of photoactive trans isomer to cis isomer due to UV rays. We have earlier developed a mean field model involving molecular explanation for two lengths in which the mutual orientation of near neighbor molecules changes from an antiparallel to a parallel configuration as the temperature lowered. In this paper, this model is extended to include the length change from trans to cis isomer. The calculated values of change in $T_{NI}$ qualitatively agree with experimental trends.
Źródło:
Acta Physica Polonica A; 2011, 120, 3; 462-467
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Enhancement of Nematic Order of Liquid Crystals in Thin Cells
Autorzy:
Aswini, P.
Govind, A.
Powiązania:
https://bibliotekanauki.pl/articles/1489838.pdf
Data publikacji:
2012-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.Gd
61.30.-v
64.70.mf
Opis:
Experimental observations show that the nematic order parameter is significantly enhanced as the thickness of the cell is reduced. Calculations of earlier theories do not agree well with the experimental data. We propose a simple extension of Maier-Saupe theory to account for the enhancement. A molecule near the surface is assumed to feel the mean field potential (the Maier-Saupe type) and also the surface induced potential. This is included in the Maier-Saupe theory. Our calculations are in better agreement with the experimental data.
Źródło:
Acta Physica Polonica A; 2012, 121, 3; 625-627
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical study of nematic to isotropic transition in porous media
Autorzy:
Govind, A.
Banerjee, Kumarii
Powiązania:
https://bibliotekanauki.pl/articles/1075553.pdf
Data publikacji:
2016-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
61.30.Cz
64.70.M-
61.30.Pq
Opis:
Experimental observations show that the N-I transition temperature (T_{NI}) for liquid crystals embedded in solid porous materials is lower compared to that of the bulk liquid crystals and T_{NI} is reduced linearly with the inverse pore diameter. To explain this, various theoretical studies have been proposed. We propose to use the mean field approach. We modify the Maier-Saupe mean field theory to include the disordering effects of porosity as a disordering surface potential. A molecule near the surface is assumed to feel the mean field potential (the Maier-Saupe type) and also the surface induced potential. We calculate the values of the nematic order parameter and hence find the T_{NI} for different pore diameters. The weighted average of the order parameter is calculated considering the cylindrical symmetry of the pores. Our calculations on the variation of T_{NI} with pore diameter agree with experimental data. Also, the calculated values of specific heat peak decrease with decrease in pore radius, in agreement with experimental trends.
Źródło:
Acta Physica Polonica A; 2016, 130, 3; 748-750
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determination of Orientational Order Parameters of Two Tri-Component Mixtures from Optical Birefringence and X-Ray Diffraction Measurements
Autorzy:
Basak, S.
Dasgupta, P.
Das, B.
Das, M.
Dabrowski, R.
Powiązania:
https://bibliotekanauki.pl/articles/1492775.pdf
Data publikacji:
2011-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.05.cp
61.30.-v
42.70.Df
Opis:
Two tri-component mixtures as base mixtures for vertically aligned mode LCD's were prepared. The eutectic compositions were theoretically estimated and experimentally verified from differential scanning calorimetry studies. A room temperature nematic mixture with fairly broad operating range emerged from each of the tri-component mixtures. The optical birefringence of these mixtures at the eutectic composition was measured as a function of temperature. X-ray diffraction measurements were done on these mixtures to obtain the orientational order parameters as a function of temperature. The order parameter values were also determined from birefringence measurements and the results were compared with mean field theory. Structural parameters like intermolecular distance and apparent molecular length have also been determined.
Źródło:
Acta Physica Polonica A; 2011, 120, 6; 1037-1042
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
First Order Hyperpolarizabilities, NPA and Fukui Functions of Cyclohexanone by Density Functional Theory Method
Autorzy:
Gangadharan, Rubarani
Sampath Krishnan, S.
Powiązania:
https://bibliotekanauki.pl/articles/1398896.pdf
Data publikacji:
2015-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
78.30.Jw
31.15.Ew
Opis:
The molecular structure of cyclohexanone was calculated by the B3LYP density functional model with 6-311++G(d,p) basis set by Gaussian program. The results from natural bond orbital analysis have been analyzed in terms of the hybridization of atoms and the electronic structure of the title molecule. The formation of hydrogen bond was investigated using natural bond orbital calculation. The electron density based local reactivity descriptors such as Fukui functions were calculated. The dipole moment (μ) and polarizability (α), anisotropy polarizability (Δα) and first order hyperpolarizability ($β_\text{tot}$) of the molecule have been reported. Thermodynamic properties of the title compound were calculated at different temperatures.
Źródło:
Acta Physica Polonica A; 2015, 127, 3; 748-752
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Density Functional Theory Studies on Ir Spectra of the Triphenylene Derivatives. A Scaled Quantum Mechanical Force Field Approach
Autorzy:
Merkel, K.
Kocot, A.
Wrzalik, R.
Orgasińska, B.
Powiązania:
https://bibliotekanauki.pl/articles/2014386.pdf
Data publikacji:
2000-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
31.15.Ew
78.30.Jw
Opis:
Density functional theory, B3-LYP with the 6-31G$\text{}^{*}$ basis set was applied to study the structures and vibrational infrared spectra of triphenylene and the hexasubstituted triphenylene derivatives. The calculated force fields were scaled using the scaled quantum mechanical force field method. The predicted vibrational frequencies were compared with the experimental IR spectra (500-4000cm$\text{}^{-1}$). The spectra were interpreted and vibrational assignments were reported. This study shows that the scaled density functional force field approach enables, through the transferability of scale factors, good interpretation of vibrational spectra of large molecules.
Źródło:
Acta Physica Polonica A; 2000, 98, 5; 525-531
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlation Length in PBnA Liquid Crystal Family
Autorzy:
El Guermai, K.
Ayadi, M.
El Boussiri, K.
Powiązania:
https://bibliotekanauki.pl/articles/1992845.pdf
Data publikacji:
1998-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
61.10.-i
64.70.Md
61.30.Gd
Opis:
We present a study of the range molecular interactions inside layers in smectic phases A and I of PBnA (phenyl-4 benzylidene 4'-alkylaniline) liquid crystals family. The purpose of this work is to determine the correlation length of the molecules' gravity centers in existing domain of smectic phases and at the transition between them. We used X-rays in-plane peaks of the pattern diffraction of aligned sample by a magnetic field.
Źródło:
Acta Physica Polonica A; 1998, 94, 5-6; 779-784
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Singular Elastic Properties of Mixtures with the Re-entrant Nematic Phase
Autorzy:
Czechowski, G.
Jadżyn, J.
Powiązania:
https://bibliotekanauki.pl/articles/2038376.pdf
Data publikacji:
2004-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.70.Md
62.20.Dc
61.30.-v
Opis:
The paper presents temperature behavior of the splay and bend elastic constants measured for n-hexyloxycyanobiphenyl and n-octyloxycyanobiphenyl mixtures - a system exhibiting the re-entrant nematic phase. It was shown that singularities in the elastic properties of the system concern not only the nematic phase (the well-known pre-smectic effects) but first of all - the smectic A phase, in which the splay and bend deformations, normally not allowed for the layered structures, can be induced.
Źródło:
Acta Physica Polonica A; 2004, 106, 4; 475-485
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Equimolecular Mixture of Calamitic and Bent-Core Thiobenzoates
Autorzy:
Chruściel, J.
Wantusiak, B.
Ossowska-Chruściel, M.
Powiązania:
https://bibliotekanauki.pl/articles/1419573.pdf
Data publikacji:
2012-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
64.70.M-
78.15.+e
Opis:
This article reports on the new results on phase transitions, mesomorphic and electro-optical properties of new equimolecular mixture of calamitic and bent-core thiobenzoates. Two following liquid crystals were the components of the binary mixture: (S)-(+)-4-(1-methylheptyloxy)biphenyl 4'-octylthiobenzoate (MHOBS8) having rode-like, calamitic-chiral molecules possessing among others ferroelectric smectic C (SmC*) and bis [4-(4'-octylphenylthiocarbonyl)phenyl] isophtalates from a homologous series of banana-shaped thioesters, referred to as IFOS8, where n = 8 denoted the number of carbon atoms in terminal alkyl chains in both mesogens, synthesized by us. The IFOS8 compound has two enantiotropic phases: B2 with antiferroelectric order and B6. The mesomorphic properties were investigated by means of three complementary methods: differential scanning calorimetry, polarized light optical microscopy, and transmitted light intensity. Electro-optical measurements were also carried out.
Źródło:
Acta Physica Polonica A; 2012, 122, 2; 375-377
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal Stability of Bent-Core Liquid Crystals Doped with Magnetic Nanoparticles
Autorzy:
Juríková, A.
Csach, K.
Miškuf, J.
Tomašovičová, N.
Mitróová, Z.
Závišová, V.
Koneracká, M.
Kopčanský, P.
Timko, M.
Éber, N.
Fodor-Csorba, K.
Vajda, A.
Powiązania:
https://bibliotekanauki.pl/articles/1387994.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.-v
64.70.mj
65.80.-g
Opis:
In the work phase transitions in bent-core liquid crystals were studied using differential scanning calorimetry. For the binary mixture of bent-core molecules with 50 wt% of rod-shaped compound, the nematic to smectic transition occured below 40°C and the crystallization temperature shifted to sub-ambient temperatures. The influence of doping of the bent-core liquid crystals with magnetic nanoparticles on the kinetics of observed phase transitions was studied. The phase transition temperatures were shifted depending on the nanoparticle type and changed with varying cooling rate for all studied liquid crystal samples.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 638-640
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 21

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