Viscosity coefficients in the isotropic phase of a nematic liquid crystal

Martinoty, P.; Kiry, F.; Nagai, Satoshi; Candau, S. J.; Debeauvais, F.

doi:10.1051/jphys:01977003802015900

Cited by 38 publications

(27 citation statements)

References 9 publications

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“…This value of g is close to the bulk values, reported by others [18,19]. For a 3 mm film, the relaxation rate of the excitations goes to zero for q !…”

supporting

confidence: 90%

Confinement Effects on the Collective Excitations in Thin Nematic Films

et al. 1998

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The influence of confinement on the spectrum of collective excitations in ultrathin nematic layers of octylcyanobiphenyl is studied, using quasielastic light scattering in planarly and hybridly aligned films. Both systems show confinement-induced relaxation rate gaps in the originally gapless spectrum of director fluctuations. On the mesoscopic scale, the magnitude of the relaxation rate gap scales as the inverse thickness of the nematic layer and can be very well described by a Landau -de Gennes theory, in which the boundary conditions play an important role. [S0031-9007(98)

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“…This value of g is close to the bulk values, reported by others [18,19]. For a 3 mm film, the relaxation rate of the excitations goes to zero for q !…”

supporting

confidence: 90%

Confinement Effects on the Collective Excitations in Thin Nematic Films

et al. 1998

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“…The sample is appropriate for examination of the proposed method, because the reorientational relaxation frequencies can be changed by changing the temperature because of the strong reorientational cooperativity of pretransitional phenomena at temperature being near the isotropic to nematic phase transition 9) and thus the induced birefringence due to ultrasound is considerably large. In addition, the reorientational relaxation frequency 13) and the flow birefringence 14) for 5CB have already been reported. Those are required for the theoretical estimation.…”

Section: )mentioning

confidence: 89%

“…35 °C. For 5CB, the relaxation decay rate of reorientation Γ 13) and the flow birefringence per unit strain rate ∆n f /γ 14) in the isotropic phase were obtained. We list those at 40, 50 and 60 °C in Table I.…”

Section: )mentioning

confidence: 99%

Complex Strain-Optical Coefficient Measurements by Means of Polarization Analysis of a Diffracted Light by Longitudinal Ultrasound

Matsuoka

Miyashita

Koda

2011

J. Soc. Rheol., Jpn

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The theory to obtain the complex strain-optical coefficients was described for the liquids from polarization analysis of a diffracted light by longitudinal ultrasound. The polarization analyses on the isotropic phase of liquid crystal, 4-cyano-4'-pentylbiphenyl (5CB) were carried out at 40, 50 and 60 °C in the frequency range from 5 to 25 MHz. For the +1st and −1st order diffracted lights, values of change in arc tangent of the ratio of electric field and the phase retardation between two polarizations were obtained as functions of square of the Raman-Nath parameter. From intercepts of those values, the complex strain-optical parameters were determined. The frequency dependences of the complex strain-optical parameters at 40, 50 and 60 °C were obtained and compared with those calculated by using the data of using the reorientational relaxation frequency and the flow birefringence per unit strain rate. Although some discrepancies are found at 40 and 50 °C, the results indicate applicability the proposed method to determine the strainoptical coefficients above MHz range.

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“…2 are calculated ones obtained by substituting into Eq. ͑30͒ the values of ͉⌬n f /G͉ from flow birefringence measurements 11 and ⌫ from optical beating light scattering experiments. 26 The values of ͉⌬n f /G͉ are 1.86 and 1.26 ns and those of ⌫/2 are 10.0 and 15.3 MHz at 50 and 55°C, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…[9][10][11][12][13][14][15][16][17][18] Theories for the flow birefringence and the depolarized VH light scattering were constructed independently on the basis of the de Gennes' phenomenological thory 9-12 and irreversible statistical mechanics. [12][13][14][15][16][17][18] In both theories, the coupling of reorientational mode to the shear mode was taken into account.…”

Section: Introductionmentioning

confidence: 99%

On the frequency dependence of ultrasonically induced birefringence in isotropic phase of liquid crystal: 5CB (p-n-pentyl p′-cyanobiphenyl)

Matsuoka

Yasuda

Koda

et al. 1999

The Journal of Chemical Physics

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Theoretical expressions for the ultrasonically induced birefringence of liquids are obtained in the frame work of de Gennes’ phenomenological theory. The intensity and frequency dependence of ultrasonically induced birefringence in the isotropic phase of p-n-pentyl p′-cyanobiphenyl (5CB) was measured in order to examine the usefulness of birefringence measurements for investigating dynamical properties liquids. The observed birefringence was proportional to the square root of ultrasonic intensity. The birefringence divided by the square root of ultrasonic intensity increases with increasing frequency and appears to saturate when the ultrasonic frequency approaches the relaxation frequency of molecular reorientation. The observed values of birefringence were reproduced satisfactorily by the expression derived in this paper.

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Viscosity coefficients in the isotropic phase of a nematic liquid crystal

Abstract: Using various techniques, we measured for p-n-pentyl p'-cyanobiphenyl the three viscosity coefficients featured in de Gennes' phenomenological theory of the isotropic phase of a nematic liquid crystal

Cited by 38 publications

References 9 publications

Confinement Effects on the Collective Excitations in Thin Nematic Films

Confinement Effects on the Collective Excitations in Thin Nematic Films

Complex Strain-Optical Coefficient Measurements by Means of Polarization Analysis of a Diffracted Light by Longitudinal Ultrasound

On the frequency dependence of ultrasonically induced birefringence in isotropic phase of liquid crystal: 5CB (p-n-pentyl p′-cyanobiphenyl)

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