Bend and splay elastic constants and the rotational viscosity of nematic decylammonium chloride and ammonium chloride water mixtures

Haven, Tom; Armitage, David; Saupe, A.

doi:10.1063/1.441787

Cited by 49 publications

(24 citation statements)

References 8 publications

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“…The data DH vs x in [12,14 ] also satisfy our theoretical equation (25). Using equations (20) and (22) From equation (21), when S is xed, T vs x should be we get T + NI Õ T NI 5 b2 /216a 0 c, which decreases with cona straight line. Equation (21) may be written as centration as the coeYcients b and c decrease, which agrees with the experimental results of Boden et al [13].…”

Section: Introductionmentioning

confidence: 98%

“…We therefore assume a linear form for with the experiments [3, 11,12,14,18 ]. The experi-T * NI , mental data for the heat capacity measurements [12,14] near the N+ D -I transition show that the measured values We therefore tted equation (20) with the experiabsence of any concentration-order parameter coupling. mental data of Shin et al [12,14].…”

Section: Introductionmentioning

confidence: 99%

“…In a recent study Jolley et al [18] observed a very weakly rst order transverse to the nematic symmetry axis. In experimental studies [3,19,20], the binary mixture of a caesium N+ D -I transition of the binary cesium pentadeca uorooctanoate (CsPdFO)-water system over the entire range per uorooctanoat e (CsPFO) and water produces an N+ D phase, and the binary mixture of decylammonium of experimentally accessible concentrations~0.07-0.40, which of course rules out the possibility of a Landau chloride (DACl) micelles and water-ammonium chloride (NH 4 Cl) solution produces an NÕ D phase. point.…”

Section: Introductionmentioning

confidence: 99%

“…coeYcients b, c and m using the relations (19), (20 ) and (25), with the corresponding experimental data for each The order parameter S(x, T ) in the N+ D phase is given concentration. But we have not repeated the calculations by since such calculations are already available in the literature [14,26].…”

Section: Introductionmentioning

confidence: 99%

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Nematic-isotropic phase transition in lyotropic liquid crystals

Mukherjee¹

2002

Liquid Crystals

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We propose a Landau-de Gennes phenomenological model to describe the nematic-isotropic phase transition in lyotropic liquid crystals. The possibility of a rst or second order transition is explored by means of the variation of the concentration of surfactant. We show that a Landau point on the nematic-isotropic phase transition line can be achieved under certain conditions. The theoretical predictions are found to be in good qualitative agreement with available experimental results.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nematic-isotropic phase transition in lyotropic liquid crystals

Mukherjee¹

2002

Liquid Crystals

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“…Typically e a ^0.65 in thermotropics; it is -0.0065 in DAC1. 3 From the time decay of the autocorrelation function we measure (i) 2 (q s /2) 2 (7] a q x 2 + ^q 2 )' 1 and y x is the director twist viscosity. The fluid viscosities for various orientations of n and velocity v are rj a (with niv, n±Vv) 9 r\ b (with n ||v, n-LVv), and t] c (with n^-v, n||vt>).…”

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confidence: 99%

Orientational Fluctuations of a Lyotropic Nematic Liquid Crystal Measured by Quasielastic Light Scattering

Kumar

Litster

1983

Phys. Rev. Lett.

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The nematic-isotropic and the nematic-to-lamellar phase changes in the lyotropic liquid crystal formed by decylammonium chloride micelles in a water-ammonium chloride solution have been studied by light scattering. The former transition shows behavior identical to that observed in thermotropic liquid crystals. The nematic-lamellar transition appears closely similar to a thermotropic nematic-smectic-A change and the elastic constants diverge according to the analogy to superfluid helium and the three-dimensional xy model. 64.70.Ew, Lyotropic mesophases are formed by surfactant molecules in a suitable solvent, which is often an aqueous electrolyte. They exhibit a variety of ordered phases depending on temperature and solvent concentration. Many of these phases seem analogous to phases that exist in thermotropic liquid crystals. Lamellar or neat soap phases, for example, are similar to thermotropic smectic-A and -C phases while the hexagonal or middle soap phases may be analogous to the columnar discotic phase. The first lyotropic phase to orient readily in a magnetic field was described by Lawson and Flautt 1 ; Reeves and his colleagues recognized that these phases were lyotropic analogs to nematics and elucidated many of their properties. 2 Although a great deal is known about lyotropic liquid-crystalline order, the exact structure of many phases and the nature of transitions from one phase to another, as well as details of their similarities to, and differences from, thermotropic phases, are relatively unexplored. The nematic lyotropics are formed by the interaction of nonspherical micelles which are designated type I or type II according to whether the diamagnetic anisotropy is greater along or transverse to the nematic symmetry axis. 2 Either type-I or type-II nematics may, in principle, be formed by the orientational ordering of the symmetry axes of either disklike (DM) or rod-like (CM) micellar solutions. The DM nematic phase may also have a second-order transition to a neat soap or lamellar phase which appears closely similar to the thermotropic nematic-smectic-A transition. Prior studies 3 strongly suggest that lyotropic and thermotropic nematics have the same symmetry and that the neat soap phases that form from them are similar to thermotropic smectic -A phases. Since we believe that the properties of these ordered phases are determined by symmetry and spatial dimensionality, behavior of the lyotropic nematic phases and their analogs should be identical. In particular, breaking the orientational symmetry should result in lyotropic nematic Goldstone modes identical to thermotropic director modes and the behavior of the neat soap (smectic A) to nematic as well as the nematic to isotropic phase changes should be identical to those in thermotropic materials. These expectations can be tested by quasielastic light scattering and we report such measurements in this paper. We found the behavior of the lyotropic material we studied, decylammonium chloride micelles in aqueous solution of ammonium chloride, to be e...

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Liquid Crystals, Structure of

Litster

Shashidhar

2003

Digital Encyclopedia of Applied Physics

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Bend and splay elastic constants and the rotational viscosity of nematic decylammonium chloride and ammonium chloride water mixtures

Cited by 49 publications

References 8 publications

Nematic-isotropic phase transition in lyotropic liquid crystals

Nematic-isotropic phase transition in lyotropic liquid crystals

Orientational Fluctuations of a Lyotropic Nematic Liquid Crystal Measured by Quasielastic Light Scattering

Liquid Crystals, Structure of

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