Observation of liquid crystals confined in an elliptic cylinder

Jeong, Joonwoo; Kim, Mahn Won

doi:10.1063/1.4745773

Cited by 10 publications

(6 citation statements)

References 32 publications

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“…For example, nematics confined in elliptic cylinders with homeotropic anchoring can show escaped-radial configuration for micro-meter size; 38 For example, nematics confined in elliptic cylinders with homeotropic anchoring can show escaped-radial configuration for micro-meter size; 38 …”

Section: Model Extensionmentioning

confidence: 99%

Disclination elastica model of loop collision and growth in confined nematic liquid crystals

et al. 2015

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Theory and modeling are used to characterize disclination loop-loop interactions in nematic liquid crystals under capillary confinement with strong homeotropic anchoring. This defect process arises when a mesogen in the isotropic phase is quenched into the stable nematic state. The texture evolution starts with +1/2 disclination loops that merge into a single loop through a process that involves collision, pinching and relaxation. The process is characterized with a combined Rouse-Frank model that incorporates the tension and bending elasticity of disclinations and the rotational viscosity of nematics. The Frank model of disclinations follows the Euler elastica model, whose non-periodic solution, known as Poleni's curve, is shown to locally describe the loop-loop collision and to shed light on why loop-loop merging results in a disclination intersection angle of approximately 60°. Additional Poleni invariants demonstrate how tension and bending pinch the two loops into a single +1/2 disclination ring. The Rouse model of disclination relaxation yields a Cahn-Hilliard equation whose time constant combines the confinement, tension/bending stiffness ratio and disclination diffusivity. Based on predictions made using this three stage process, a practical procedure is proposed to find viscoelastic parameters from defect geometry and defect dynamics. These findings contribute to the evolving understanding of textural transformations in nematic liquid crystals under confinement using the disclination elastica methodology.

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Section: Model Extensionmentioning

confidence: 99%

Disclination elastica model of loop collision and growth in confined nematic liquid crystals

et al. 2015

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“…The miniaturization trends in electronics and optoelectronics, but also the general goal to manipulate and understand matter at the nanoscale has motivated detailed studies of the structural, dynamical and thermodynamical properties of confined and semiconfined achiral mesogens. , Despite recent experimental advancements to directly probe orientational order parameter profiles in the proximity of planar, solid walls, − achieving the spatial (and temporal) resolution necessary to rigorously explore these phenomenologies at the nanoscale remains experimentally extremely demanding. Still, it could be revealed that both the collective orientational (I–N) and the translational (Sm–I or Sm–N) transitions are significantly affected by finite size and interfacial (solid–liquid or liquid–liquid) interactions introduced by confining walls − or the geometrical constraints in nanoporous media. ,− …”

Section: Introductionmentioning

confidence: 99%

Chiral Phases of a Confined Cholesteric Liquid Crystal: Anchoring-Dependent Helical and Smectic Self-Assembly in Nanochannels

et al. 2016

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Chiral liquid crystals (ChLCs) allow a fundamental insight into the interplay of molecular chirality and the formation of macroscopic, self-assembled helices. They also exhibit unique optical properties, in particular huge polarization rotation, which is employed in a wide range of photonic technologies. Here, we present a study of linear and circular optical birefringence in combination with X-ray diffraction experiments on an archetypical ChLC, i.e., the cholesteric ester CE6, confined in cylinders of mesoporous alumina and silica with distinct polymer surface graftings resulting in normal or tangential wall anchoring. The unconfined ChLC exhibits a discontinuous, first-order isotropic-to-chiral nematic (cholesteric) phase transition with the formation of double-twist helices and a discontinuous cholesteric-to-smectic A transition. The thermotropic behavior of the confined ChLC, explored in a channel radii range of 7–21 nm, deviates substantially from bulk behavior. There is no isotropic state. In contrast, a chiral paranematic phase with a preferred arrangement of the ChLC at the channel wall is found. For normal anchoring, a radial-escape structure evolves upon cooling. The phase transition to the smectic phase is completely suppressed. For tangential anchoring, a large optical activity indicates a continuous paranematic-to-cholesteric transition with double-twist helices aligned parallel to the long axes of the cylinders. Upon cooling, these helical structures, known as basic building blocks of blue ChLC phases, transform in a continuous manner to a cylinder-aligned smectic A phase.

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“…12,13 In still other confined geometries with various boundary conditions, SmA LCs can self-assemble into more complicated textures; one such texture that relieves frustration in a mathematically elegant way is called the focal conic domain (FCD). [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] In this contribution, we explore the textures of 4 0 -octyl-4biphenylcarbonitrile (8CB) in the SmA phase, within bowlshaped cavities of Janus droplets with homeotropic boundary conditions wherein molecular orientation is perpendicular to the interface. Previously, we have reported on fabrication methods and observations associated with nematic LC Janus droplets (of 4 0 -pentyl-4-biphenylcarbonitrile, 5CB).…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Focal conic flowers, dislocation rings, and undulation textures in smectic liquid crystal Janus droplets

et al. 2022

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Observation of liquid crystals confined in an elliptic cylinder

Cited by 10 publications

References 32 publications

Disclination elastica model of loop collision and growth in confined nematic liquid crystals

Disclination elastica model of loop collision and growth in confined nematic liquid crystals

Chiral Phases of a Confined Cholesteric Liquid Crystal: Anchoring-Dependent Helical and Smectic Self-Assembly in Nanochannels

Focal conic flowers, dislocation rings, and undulation textures in smectic liquid crystal Janus droplets

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