Phase diagrams of mixtures of a polymer and a cholesteric liquid crystal under an external field

Matsuyama, Akihiko

doi:10.1063/1.4901085

Cited by 8 publications

(4 citation statements)

References 44 publications

(88 reference statements)

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“…The effect of magnetic fields on the temperature at which the cholesteric crystalline state to isotropic state transition occurs is important because these devices are to be used at varying magnetic fields (0.5 T to 7 T). Previous studies on LCs show negligible effects (less than 0.1°C) on the transition temperature for a small sampling of LC molecules …”

Section: Theorymentioning

confidence: 84%

MRI‐visible liquid crystal thermometer

Keenan

Stupic

Russek

et al. 2020

Magnetic Resonance in Med

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Purpose: MRI parameters, such as T 1 , T 2 , and ADC, of tissue-mimicking materials in MRI phantoms can exhibit temperature dependence, and bore temperatures can vary over a 10°C range across different MRI systems. If this variation is not accurately corrected for, the quantitative nature of reference or phantom measurements is irrelevant. Available thermometers require opening the phantoms to probe the temperature, which can introduce contaminants that may affect the stability and accuracy of the phantom. An integrated, MRI-visible thermometer that can be read using typical imaging protocols is needed. Theory and Methods: An MRI-compatible thermometer was designed using liquid crystals (LCs) that exhibit rapid transitions between the LC cholesteric state and isotropic state in the room temperature range spanning 17°C to 23°C in 1.0°C increments. The LC thermometer was assessed visually and using superconducting quantum interference device magnetometry, NMR, and MRI techniques. Results: The signal generated from the LC thermometer was visible with spin-echo and gradient-echo MRI images. The LC state transition temperatures were visually referenced to a National Institute of Standards and Technology-traceable thermometer, and these LC state transitions were confirmed using superconducting quantum interference device magnetometry and NMR. Conclusions: The LC MR-visible thermometer had measurable changes in relative signal with temperature, which were invariant to a variety of imaging sequences used.

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Section: Theorymentioning

confidence: 84%

MRI‐visible liquid crystal thermometer

Keenan

Stupic

Russek

et al. 2020

Magnetic Resonance in Med

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“…The ϵ does not depend on z and remains constant. Based on the Matsuyama theories [21,23,24] of a N TB phase and molecular field theory for the N* phase of Liu-Liu and coworkers [37,38], we introduce the expression for the N TB phase by including the third-order Legendre polynomial term in the chiral part of interaction potential in addition to second-order Legendre polynomial term. Let N L be the number of LC molecules of length L and diameter D.…”

Section: Free Energy Relation For a Twist-bend Nematic Phasementioning

confidence: 99%

“…In an interesting work, Matsuyama [21] introduced a meanfield theory to describe N TB phase. Based on the previous works [23,24] of the N* phase, the coupling between nematic director and pitch axis of N TB phase has been incorporated. Barbero et al [36] developed an elastic theory for the description of N TB phase by taking into account such a coupling term.…”

Section: Introductionmentioning

confidence: 99%

Twist-Bend Nematic Phase: Role of Third-Order Legendre Polynomial Term in Chiral Interaction Potential

2020

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Using a mean-field theory, a twist-bend nematic (N TB) phase has been described. In addition to second-order Legendre polynomial term, the chiral interaction potential includes third-order Legendre polynomial term also. It considers the coupling between a nematic director and a pitch axis of the N TB phase. The distortion free energy, order parameter for twist-bend nematic, and orientational distribution function in equilibrium state have been calculated. Based on the free energy minimization, we obtain that the inclusion of third-order Legendre polynomial term in interaction energy makes N TB phase more stable.

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“…The temperature and concentration dependence of the CLC helical pitch has been widely reported. 7 Recently Matsuyama 49,50 showed that the helical pitch of a cholesteric phase is a function of the concentration and the orientation order parameter in a mixture of polymer and a liquid crystal. In the present study, we assume that the helix pitch changes in response to humidity level from the swelling and shrinking of the polysaccharide matrix through water sorption.…”

Section: A Geometry and Structurementioning

confidence: 99%

Tunable nano-wrinkling of chiral surfaces: Structure and diffraction optics

Rofouie

Pasini

Rey

2015

The Journal of Chemical Physics

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Periodic surface nano-wrinkling is found throughout biological liquid crystalline materials, such as collagen films, spider silk gland ducts, exoskeleton of beetles, and flower petals. These surface ultrastructures are responsible for structural colors observed in some beetles and plants that can dynamically respond to external conditions, such as humidity and temperature. In this paper, the formation of the surface undulations is investigated through the interaction of anisotropic interfacial tension, swelling through hydration, and capillarity at free surfaces. Focusing on the cellulosic cholesteric liquid crystal (CCLC) material model, the generalized shape equation for anisotropic interfaces using the Cahn-Hoffman capillarity vector and the Rapini-Papoular anchoring energy are applied to analyze periodic nano-wrinkling in plant-based plywood free surfaces with water-induced cholesteric pitch gradients. Scaling is used to derive the explicit relations between the undulations' amplitude expressed as a function of the anchoring strength and the spatially varying pitch. The optical responses of the periodic nano-structured surfaces are studied through finite difference time domain simulations indicating that CCLC surfaces with spatially varying pitch reflect light in a wavelength higher than that of a CCLC's surface with constant pitch. This structural color change is controlled by the pitch gradient through hydration. All these findings provide a foundation to understand structural color phenomena in nature and for the design of optical sensor devices.

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Phase diagrams of mixtures of a polymer and a cholesteric liquid crystal under an external field

Cited by 8 publications

References 44 publications

MRI‐visible liquid crystal thermometer

MRI‐visible liquid crystal thermometer

Twist-Bend Nematic Phase: Role of Third-Order Legendre Polynomial Term in Chiral Interaction Potential

Tunable nano-wrinkling of chiral surfaces: Structure and diffraction optics

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