Dielectric Properties of a Nematic Binary Mixture

Garg, Shila; Spears, Tom

doi:10.1080/15421400490431705

Cited by 10 publications

(6 citation statements)

References 3 publications

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“…The possibility of formation of such homoand heterocomplexes was proposed earlier by others [25,26]. Garg and Spears from their molecular modelling on a related system showed a strong interaction between two species forming a hybrid molecule [27]. Such cross-interaction is also proposed by Kyu et al [28,29] from their theoretical work on induced smectic A phases.…”

Section: X-ray Diffraction Measurementssupporting

confidence: 51%

Study of the physical properties of a mesogenic mixture showing induced smectic A_dphase by refractive index, density and x-ray diffraction measurements

Roy¹,

Prasad²,

Das³

2009

J. Phys.: Condens. Matter

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The binary mixture of 4-n-pentyl phenyl 4-n'-hexyloxy benzoate (ME6O.5) and p-cyanophenyl trans-4-pentyl cyclohexane carboxylate (CPPCC) shows the presence of an induced smectic A(d) phase in a certain concentration range 0.030.33, whereas there is a discontinuity in these values for mixtures with x<0.33, consistent with the density and transition entropy measurements done on this system. The orientational order parameter, measured from x-ray diffraction studies, are somewhat smaller than those obtained from refractive index measurement in the induced smectic phase for all the mixtures. In the smectic phase, the OOP values initially increases with molar concentration up to x = 0.24 and then decreases showing a broad minima around x = 0.4. The variation of layer thickness in the induced smectic phase with composition has been explained by assuming the formation of homo- and heterodimers. We conclude that the possible packing of molecules in the induced smectic A(d) phase stabilizes the layers but increases the orientational free volume, consistent with the lower orientational order parameter.

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Section: X-ray Diffraction Measurementssupporting

confidence: 51%

Study of the physical properties of a mesogenic mixture showing induced smectic A_dphase by refractive index, density and x-ray diffraction measurements

Roy¹,

Prasad²,

Das³

2009

J. Phys.: Condens. Matter

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“…However, it is to be noted that these reported values of ε iso were measured at a frequency of 10 kHz or more. An attempt was made to fit the ε av values to equation ( 6), and ε iso to equation (7):…”

Section: Resultsmentioning

confidence: 99%

“…However, the physical properties of such mixtures cannot always be interpolated from the properties of the pure components. One such example is the induced smectic phase that is generally formed in binary mixtures of pure nematogenic compounds, one having a terminal polar end and the other being non-polar [1][2][3][4][5][6][7][8][9][10]. Strong induction of smectic A d (SmA d ) is also possible in mixtures of polar nematic compounds [11][12][13], some of which also exhibit the re-entrant nematic (N re ) phase.…”

Section: Introductionmentioning

confidence: 99%

Static dielectric properties of two nematogenic compounds and their binary mixtures showing induced smectic A_dand re-entrant nematic phases

Prasad¹,

Das²

2011

Phys. Scr.

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Static dielectric permittivity measurements on a binary system of 4-cyanophenyl [4 (4 -n-heptylphenyl)] benzoate (referred to as 7CPB) + 4-cyanophenyl 4-nonylbenzoate (referred to as 9.CN) showing both induced smectic A d and re-entrant nematic phases in a certain concentration range (0.4 < x 9.CN < 0.87) are being reported. The temperature variation of permittivities at the nematic-smectic A d and smectic A d -re-entrant nematic transition for all the mixtures are found to be continuous. In the case of the mixture with x = 0.662, the parallel component of dielectric permittivity shows a pronounced decrease in the smectic A d phase due to dipole-dipole correlation. A similar effect is seen in other mixtures but on a reduced scale. Mesogenic molecular dipole moments µ and their inclination angles β with the molecular long axis have also been determined following the Maier and Meier equations. The effective values of the dipole moments (µ eff ) in the mixtures are found to be less than those observed in the pure compounds. Moreover, µ eff in the smectic A d phase is seen to be slightly smaller than that obtained by extrapolation from either the nematic or the re-entrant nematic phases. The lower effective dipole moment in the smectic A d phase indicates the development of additional anti-parallel ordering of the molecular dipoles in the induced smectic phase.

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“…However, in principle they are usually considered to confer one main feature. Therefore, a mixture of different compounds might have different optical and electrical properties, phase transitions, [13], dielectric properties as a function of temperature, [14,15] and the mixture itself can open up new opportunities in the LCD panel market. One of the interesting features of LC mixtures is that they exhibit the so-called reentrant phenomenon which is a reappearance of the high temperature phase with a higher symmetry upon cooling down.…”

Section: Introductionmentioning

confidence: 99%

Visible spectroscopy of 5CB/8CB liquid crystals

et al. 2015

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Electro-optical properties of nematic liquid crystals (LCs) have attracted a great deal of research interest and have resulted in a number of practical applications in many areas. In the present study, wavelength dependence of electro-optical properties of two different types of nematic LCs and their binary mixtures are investigated. LCs used in this study are 5CB and 8CB and their mixtures in different proportions. The optical transmittance of the structures has been studied by means of visible spectroscopy by measuring the transmitted light intensity as a function of the wavelength under various driving AC electric field values. Experiments were carried out at the wavelength interval 380À780 nm at a constant temperature of 25 C in order to see the effect of the applied field alone.

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Dielectric Properties of a Nematic Binary Mixture

Cited by 10 publications

References 3 publications

Study of the physical properties of a mesogenic mixture showing induced smectic A_dphase by refractive index, density and x-ray diffraction measurements

Study of the physical properties of a mesogenic mixture showing induced smectic A_dphase by refractive index, density and x-ray diffraction measurements

Static dielectric properties of two nematogenic compounds and their binary mixtures showing induced smectic A_dand re-entrant nematic phases

Visible spectroscopy of 5CB/8CB liquid crystals

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Dielectric Properties of a Nematic Binary Mixture

Cited by 10 publications

References 3 publications

Study of the physical properties of a mesogenic mixture showing induced smectic Adphase by refractive index, density and x-ray diffraction measurements

Study of the physical properties of a mesogenic mixture showing induced smectic Adphase by refractive index, density and x-ray diffraction measurements

Static dielectric properties of two nematogenic compounds and their binary mixtures showing induced smectic Adand re-entrant nematic phases

Visible spectroscopy of 5CB/8CB liquid crystals

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Study of the physical properties of a mesogenic mixture showing induced smectic A_dphase by refractive index, density and x-ray diffraction measurements

Study of the physical properties of a mesogenic mixture showing induced smectic A_dphase by refractive index, density and x-ray diffraction measurements

Static dielectric properties of two nematogenic compounds and their binary mixtures showing induced smectic A_dand re-entrant nematic phases