Permeation process in columnar discotic liquid crystal subjected to steady dilation and oscillatory shear

Sanaâ, F.; Gharbia, M.; Gharbi, A.; Nguyen, H. T.

doi:10.1016/s0039-6028(01)01852-0

Cited by 6 publications

(7 citation statements)

References 19 publications

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“…With D being of the order of 10 À9 m 2 s À1 , [25] we obtain typical equilibrium times, t perm , of the order of a second for strand radii r around 30 mm, which seems reasonable. With D being of the order of 10 À9 m 2 s À1 , [25] we obtain typical equilibrium times, t perm , of the order of a second for strand radii r around 30 mm, which seems reasonable.…”

Section: Permeationmentioning

confidence: 54%

“…in which D is the diffusion constant of the discotic molecules across the array of columns. With D being of the order of 10 À9 m 2 s À1 , [25] we obtain typical equilibrium times, t perm , of the order of a second for strand radii r around 30 mm, which seems reasonable. But, as t perm arises from a diffusion process, it strongly depends on the radius of the strand.…”

Section: Permeationmentioning

confidence: 54%

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Elongation of Discotic Liquid Crystal Strands and Lubricant Effects

Bhattacharyya

Galerne

2013

ChemPhysChem

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After a short review on the physics of pulled threads and their mechanical properties, the paper reports and discusses the strand elongation of disordered columnar phases, hexagonal or lamella-columnar, of small molecules or polymers. The mechanical properties appear to be relevant to the length of the columns of molecules compared to the thread length, instead of the usual correlation length. If, taking the entanglement effect into account, the column length is short, the strand exhibits rather fluid-like properties that may even look nematic-like at the macroscopic scale. The Plateau-Rayleigh instability breaks the thread shortly thereafter. However, because the hydrodynamic objects are the columns instead of the molecules, the viscosity is anomalously large. The observations show that the strands in the columnar phases are made of filaments, or fibrils, which are bundles of columns of molecules. This explains the grooves and rings, which are observed on the antenna or bamboo-like strand profiles. On pulling a strand, the elongation stress eventually exceeds the plasticity threshold, thus breaking the columns and the filaments. As a result, cracks, more exactly, giant dislocations are formed. These change the strand thickness by steps of different birefringence colors. Interestingly, the addition of a solute may drastically change the effective viscosity of the columnar phase and its mechanical properties. Some solutes, such as alkanes, exhibit lubricant and detangling properties, whereas others such as triphenylene, are antilubricant.

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Section: Permeationmentioning

confidence: 54%

Section: Permeationmentioning

confidence: 54%

Elongation of Discotic Liquid Crystal Strands and Lubricant Effects

Bhattacharyya

Galerne

2013

ChemPhysChem

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“…, where K3 is the Franck elastic constant associated with the bending and B the normal elasticity modulus, both measured in previous works [7,8].…”

Section: Dilation Instability: Striationsmentioning

confidence: 99%

“…The response of (HCLC) to steady dilation has been investigated. The response of the aligned HCLC to rectilinear oscillatory shear has been studied [7,8]. The response of the aligned HCLC to rectilinear oscillatory shear has been studied [7,8].…”

Section: Introductionmentioning

confidence: 99%

Characterisation of The Columnar undulations Using Rayleigh Scattering

Sanaâ¹,

Yakoubi²,

Gharbia³

2007

AIP Conference Proceedings

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Rayleigh scattering in hexagonal columnar liquid crystal subjected to oscillatory shear AIP Conf. Proc. 935, 132 (2007); 10.1063/1.2795403Study of thermal transport in nanoparticle suspensions using forced Rayleigh scattering Abstract. Recently, we have presented the first Rayleigh scattering of the undulated columnar liquid crystal. Column striations (by dilation) or column bands (by alternating shear) and mode quantisation allow the scattering to be observable only for two symmetrical direction of reciprocal space. In this work, we use the scattered light to determine the instantaneous geometrical parameters of the structure.

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“…Single domains, which eliminate the presence of residual topological defects, are very useful in the Rayleigh scattering [1,2]. The response of aligned LC to rectilinear oscillatory shear was investigated for Smectic A LC [3,4], for Nematic LC [5,6,7], for Lyotropic LC [8,9], or for discotic LC [10,11]. In all cases, authors show the appearance of bands in such kinds of materials when applying alternating shear.…”

Section: Introductionmentioning

confidence: 99%

Rayleigh scattering in hexagonal columnar liquid crystal subjected to oscillatory shear

Sanaâ¹,

Gharbia²

2007

AIP Conference Proceedings

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Recently, we have presented the column instability under rectilinear oscillatory shear, and we have found the following facts: (a) By varying the shear frequency at fixed amplitude we have observed the quantification of the wave length distortion modes by the sample thickness. (b) By increasing the amplitude we provoke the undulation instability. In this work, we present the undulation of the structure, when the Hexagonal columnar liquid crystal (HCLC) is submitted to alternating shear excitation. We observe for the first time the wavelength modes using Rayleigh scattering. We discuss the obtained results in comparison with the mecano-optic measurements of the band structure. These experiments give an accurate way to measure the spatial periodicity and the temporal frequency.

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Permeation process in columnar discotic liquid crystal subjected to steady dilation and oscillatory shear

Cited by 6 publications

References 19 publications

Elongation of Discotic Liquid Crystal Strands and Lubricant Effects

Elongation of Discotic Liquid Crystal Strands and Lubricant Effects

Characterisation of The Columnar undulations Using Rayleigh Scattering

Rayleigh scattering in hexagonal columnar liquid crystal subjected to oscillatory shear

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