On the critical behavior of the layer compressional elastic constant B at the smectic A-nematic phase transition

Benzekri, M.; Marcerou, J. P.; Nguyen, H. T.; Rouillon, J. C.

doi:10.1080/01411599108207734

Cited by 3 publications

(7 citation statements)

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“…When the temperature is increased, the line tension decreases and becomes negative above T = T SN . This leads to the spontaneous nucleation and proliferation of dislocation loops, and the decay of the smectic order is reflected by the temperature dependence of the layer compression modulus B. Benzekri et al [ 51 , 52 ] showed that B decreases according to a power-law behavior with a critical exponent given by the Nelson-Toner model [ 53 ]. Using freeze-fracture transmission electron microscopy technique, Moreau et al [ 54 ] showed that dislocation loop size indeed increases in the vicinity of the SN-transition for a lyotropic liquid crystal.…”

Section: Defect Structures In the Smectic Phasementioning

confidence: 99%

Structural Rheology of the Smectic Phase

Fujii

Komura

2014

Materials

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In this review article, we discuss the rheological properties of the thermotropic smectic liquid crystal 8CB with focal conic domains (FCDs) from the viewpoint of structural rheology. It is known that the unbinding of the dislocation loops in the smectic phase drives the smectic-nematic transition. Here we discuss how the unbinding of the dislocation loops affects the evolution of the FCD size, linear and nonlinear rheological behaviors of the smectic phase. By studying the FCD formation from the perpendicularly oriented smectic layers, we also argue that dislocations play a key role in the structural development in layered systems. Furthermore, similarities in the rheological behavior between the FCDs in the smectic phase and the onion structures in the lyotropic lamellar phase suggest that these systems share a common physical origin for the elasticity.

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Section: Defect Structures In the Smectic Phasementioning

confidence: 99%

Structural Rheology of the Smectic Phase

Fujii

Komura

2014

Materials

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“…where C is a dimensionless numerical coefficient. From the previous experimental papers, it is known that K for 8CB is almost constant K = (5.2 ± 0.3) × 10 −12 N [28], while B does depend on the temperature close to T SN obeying the power law relation B = (7.5 × 10 7 ) · t 0.4±0.03 Pa [8]. With this relation, B vanishes at the transition point (t = 0) because the SmA-N transition is associated with the disruption of the layered structures.…”

Section: Origin Of Elasticitymentioning

confidence: 99%

“…These observations were attributed to the rapid increment of FCD size because the transition is induced by ‡ Present address: Department of Physics, Kyoto University, Kyoto 606-8502, Japan a smectic melting. It is known that the SmA-N transition of 8CB is very close to the second order one [8,9]. In general, softening of the elasticity in the smectic close to the transition point can be induced by defect unbinding [10].…”

Section: Introductionmentioning

confidence: 99%

Elasticity of smectic liquid crystals with focal conic domains

Fujii¹,

Komura²,

Ishii³

et al. 2011

J. Phys.: Condens. Matter

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Abstract. We study the elastic properties of thermotropic smectic liquid crystals with focal conic domains (FCDs). After the application of the controlled preshear at different temperatures, we independently measured the shear modulus G ′ and the FCD size L. We find out that these quantities are related by the scaling relation G ′ ≈ γ eff /L where γ eff is the effective surface tension of the FCDs. The experimentally obtained value of γ eff shows the same scaling as the effective surface tension of the layered systems √ KB where K and B are the bending modulus and the layer compression modulus, respectively. The similarity of this scaling relation to that of the surfactant onion phase suggests an universal rheological behavior of the layered systems with defects.

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“…c , where B is the layer compression modulus, b = md 0 is the Burger vector of integer strength m and r c is the defect core radius [40]. There are many smectic liquid crystals in which B ∼ χ 0.4 [41] and r −2 c ∼ ψ 2 ∼ χ 0.5 , where ψ is the smectic order parameter [42]. Hence, the defect line tension (τ) varies as τ ∼ χ 0.9 .…”

Section: Rheological Properties Of the Twist Grain Boundary-a Phasementioning

confidence: 99%

“…Figure 10 shows the variation of G 0 with the least square fit parameter γ = 1. Assuming a medium value of Berger's vector of integer strength m = 2 [43], B ≈ 2 × 10 6 Pa [30,41] and using the relation G 0 ≈ τ/d 2 , the calculated inter-defect spacing in the TGB A phase is d ≈ 26 nm. This calculated value is closely comparable with the experimentally-measured dislocation spacing in the TGB A phase [7].…”

Section: Rheological Properties Of the Twist Grain Boundary-a Phasementioning

confidence: 99%

A Short Review on the Rheology of Twist Grain Boundary-A and Blue Phase Liquid Crystals

Sahoo

Dhara

2018

Fluids

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Topological defects are important in determining the properties of physical systems and are known varyingly depending on the broken symmetry. In superfluid helium, they are called vortices; in periodic crystals, one refers to dislocations; and in liquid crystals, they are disclinations. The defects and the inter-defect interaction in some highly chiral liquid crystals stabilize some intermediate complex phases such as Blue Phases (BPs) and Twist Grain Boundary-A (TGB A) phases. The defect dynamics of these phases contributes to the rheological properties. The temperature range of these intermediate phases usually are very small in pure liquid crystals; consequently, a detailed experiment has been difficult to achieve. However, the temperature range could be enhanced significantly in multicomponent systems. In this review article, we discuss some recent experimental progress made in understanding the rheological properties of the wide-temperature-range TGB A and BP liquid crystals.

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On the critical behavior of the layer compressional elastic constant B at the smectic A-nematic phase transition

Cited by 3 publications

References 0 publications

Structural Rheology of the Smectic Phase

Structural Rheology of the Smectic Phase

Elasticity of smectic liquid crystals with focal conic domains

A Short Review on the Rheology of Twist Grain Boundary-A and Blue Phase Liquid Crystals

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