Stabilising liquid crystalline Blue Phases

Dierking, Ingo; Blenkhorn, W. E.; Credland, E.; Drake, W.; Kociuruba, R.; Kayser, Boris; Michael, T.

doi:10.1039/c2sm07155j

Cited by 103 publications

(79 citation statements)

References 37 publications

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“…The particles used in these experiments are typically a few nanometres in size, and stabilisation is explained in terms of defect elimination (where particles sit on the disclination lines and so reduce defect energy locally). Experiments with larger particles (100 nm or more [10]) suggest this mechanism is less effective; here one might expect the larger particles to have a more wide-ranging influence on the disclination structure. It is this regime which is the subject of this work.…”

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confidence: 99%

Large Colloids in Cholesteric Liquid Crystals

2015

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We describe a coarse-grained Landau-de Gennes model of liquid crystals (LCs) including hydrodynamics based on the Beris-Edwards equations. The model is employed to study the impact of large colloids on the long range LC defect structure in the cholesteric LC blue phases. 'Large' here means that the particle size is comparable to the cholesteric pitch, the length scale on which the LC order undergoes a helical twist. We investigate the case of a single particle, with either normal or degenerate planar anchoring, placed initially in an equilibrium blue phase LC. It is found that in some cases, well defined steady disclination structure emerges at the particle surface, while in other cases no clear steady state is reached in the simulations, and disclination reorganisation appears to proliferate through the bulk LC. These systems are of potential interest in the context of using LCs to template self-assembly of colloid structure, e.g., for opto-electronic devices. Computationally, we demonstrate a parallel approach using mixed message-passing and threaded model on graphical processing units allows effective and efficient progress for this problem.

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confidence: 99%

Large Colloids in Cholesteric Liquid Crystals

2015

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“…This can manifest itself in cholesteric liquid crystals through a reduction of the pitch of the helical superstructure [105], but also in the properties of Blue Phases, which can occur through the addition of bent-core molecules over a certain concentration regime [106]. Bent-core dopants have also been shown to widen the range of an existing Blue Phase [62]. In ferroelectric liquid crystals, bent-core molecules can increase the polarization-tilt coupling coefficient, which is the only chiral parameter in the generalised Landau expansion of FLCs.…”

Section: Bent-core Materialsmentioning

confidence: 99%

“…While most displays use the nematic phase in one way or another, and some niche applications are based on ferroelectric liquid crystals, this new display mode utilizes the Kerr effect appearing in a polymer stabilized BP. The disadvantage of the small BP existence range needs to be overcome, which may be done by the design of new materials [62,63]. The advantages are then quite dominant, especially in the production process of displays, as the step of applying an alignment layer, and subsequent rubbing can be omitted.…”

Section: Blue Phasesmentioning

confidence: 99%

Chiral Liquid Crystals: Structures, Phases, Effects

2014

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The introduction of chirality, i.e., the lack of mirror symmetry, has a profound effect on liquid crystals, not only on the molecular scale but also on the supermolecular scale and phase. I review these effects, which are related to the formation of supermolecular helicity, the occurrence of novel thermodynamic phases, as well as electro-optic effects which can only be observed in chiral liquid crystalline materials. In particular, I will discuss the formation of helical superstructures in cholesteric, Twist Grain Boundary and ferroelectric phases. As examples for the occurrence of novel phases the Blue Phases and Twist Grain Boundary phases are introduced. Chirality related effects are demonstrated through the occurrence of ferroelectricity in both thermotropic as well as lyotropic liquid crystals. Lack of mirror symmetry is also discussed briefly for some biopolymers such as cellulose and DNA, together with its influence on liquid crystalline behavior.

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“…Further materials are quantum dots [23], nanorods [24], and even biological structures [25]. Large nanoparticles and microparticles have been used to stabilize frustrated phases [26].…”

Section: Introductionmentioning

confidence: 99%

Electric-field-induced transport of microspheres in the isotropic and chiral nematic phase of liquid crystals

Gleeson

Dierking

2017

Phys. Rev. E

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Article:Oh, J, Gleeson, HF orcid.org/0000-0002-7494-2100 and Dierking, I (2017) Electric-field-induced transport of microspheres in the isotropic and chiral nematic phase of liquid crystals. Physical Review E, 95 (2). 022703. ISSN 2470-0045 https://doi.org/10.1103/PhysRevE.95.022703 © 2017 American Physical Society. This is an author produced version of a paper accepted for publication in Physical Review E. Uploaded in accordance with the publisher's self-archiving policy.eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. The application of an electric field to microspheres suspended in a liquid crystal, causes particle translation in a plane perpendicular to the applied field direction. Depending on applied electric field amplitude and frequency, a wealth of different motion modes may be observed above a threshold, which can lead to linear, circular or random particle trajectories. We present the stability diagram for these different translational modes of particles suspended in the isotropic and the chiral nematic phase of a liquid crystal, and investigate the angular velocity, circular diameter, and linear velocity as a function of electric field amplitude and frequency. In the isotropic phase a narrow field amplitudefrequency regime is observed to exhibit circular particle motion whose angular velocity increases with applied electric field amplitude, but is independent of applied frequency. The diameter of the circular trajectory decreases with field amplitudes as well as frequency. In the cholesteric phase linear as well as circular particle motion is observed. The former exhibits an increasing velocity with field amplitude, while decreasing with frequency. For the latter, the angular velocity exhibits an increase with field amplitude and frequency. The 2 rotational sense of the particles on a circular trajectory in the chiral nematic phase is independent of the helicity of the liquid crystalline structure, as is demonstrated by employing a cholesteric twist inversion compound.

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Stabilising liquid crystalline Blue Phases

Cited by 103 publications

References 37 publications

Large Colloids in Cholesteric Liquid Crystals

Large Colloids in Cholesteric Liquid Crystals

Chiral Liquid Crystals: Structures, Phases, Effects

Electric-field-induced transport of microspheres in the isotropic and chiral nematic phase of liquid crystals

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