Helical Twisting Power in Cholesteric Liquid Crystal Mixtures. I. Experimental Results

Kozawaguchi, Haruki; Wada, Masanobu

doi:10.1143/jjap.14.651

Cited by 25 publications

(13 citation statements)

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“…Case 4 is observed for mixtures of NLC with righthanded cholesterics [22,[29][30][31]. Now we consider several theoretical approaches used to explain qualitatively the concentration dependence of the pitch in binary systems.…”

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confidence: 99%

Induction of chirality in nematic phases

Chilaya

1981

Rev. Phys. Appl. (Paris)

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2014 Des dispositifs de visualisation ou d'affichage à cristaux liquides utilisent les propriétés électrooptiques ou thermotropiques particulières à la phase cholestérique quand le pas de son hélice est de l'ordre de la longueur d'onde de la lumière et quelques micromètres. Les composés les plus connus présentant naturellement cette phase avec des pas appropriés sont les esters de cholestérol; malheureusement ces corps ne sont pas très stables chimiquement. Des nématiques stables tordus, soit par mélange avec un composé chiral, soit par adjonction d'un radical chiral permettent aussi de réaliser cette phase. Dans ce cas le pas dépend d'un grand nombre de facteurs. Cet article rassemble les prédictions théoriques sur l'influence des concentrations, de la température ou du radical adjoint sur le pas et les confronte à un ensemble très complet de résultats expérimentaux originaux ou déjà connus.Abstract. 2014 Some electrooptic and thermooptic effects of cholesteric phase are used in liquid crystal visualisation and display systems provided spiral pitch is equal to a visible wavelength or several micrometers. Liquid crystals with cholesteric properties were generally cholesteric esters. Unfortunately these materials are chemically nonstable. More stable nematic liquid crystals twisted by mixing with chiral materials or by adding assimetric side chain have also cholesteric phase. In this case spiral pitch depends on many factors. This report unites theoretically predicted temperature and concentration dependence of pitch and compares it with some original or known results. Revue Phys. Appl. 16 (1981) 193-208' ' MAI 1981, Classification Physics Abstracts 61.30

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confidence: 99%

Induction of chirality in nematic phases

Chilaya

1981

Rev. Phys. Appl. (Paris)

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“…In the following experiments we have always worked in this small rotation regime where the Mauguin criterium works and for which there is no 180° error possible for cpQ. 4. The electrochiral effects.…”

Section: The Expérimental Set Upmentioning

confidence: 99%

“…The electrochiral effects. 4.1 POSITIVE CHIRAL IONS. -We have first tried to observe the electrochiral effect on mixtures of 5CB doped with a chiral salt.…”

Section: The Expérimental Set Upmentioning

confidence: 99%

“…A positive E increases 1 Q e 1 as expected, but the effect is too weak to be quantitatively analyzed. 4.2 NEGATIVE CHIRAL IONS. -We have now made the same experiments on salts which can dissociate to give negative chiral ions.…”

Section: The Expérimental Set Upmentioning

confidence: 99%

“…It is well known [2] that the dissolution of chiral molecules in a nematic transforms it into a cholesteric material, which aligns with a helical texture indicative of a spontaneous twist. Much work has been done on these mixed systems, to relate for instance the helical twisting power to the concentration of chiral molecules [1, 3,4]. Up to now, it seems that almost no investigation has been made to study the helicity induced in nematics by chiral ions, instead of neutral chiral molecules.…”

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Electrochiral effects in nematic liquid crystal-chiral salt mixtures

Zhang¹,

Durand²

1989

J. Phys. France

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2014 Une cellule hybride d'un cristal liquide nématique est un instrument commode de mesure de torsion induite, puisque l'ancrage homéotrope peut se tordre sans contrainte. Nous observons la rotation de polarisation de la lumière qui se propage à travers une telle cellule hybride, dopée par des ions chiraux. Un champ électrique continu entraîne les ions dans, ou hors de, la zone où la torsion induite se voit optiquement. Il en résulte un effect électrochiral linéaire. Aux grands champs, l'effet quadratique de déformation de texture et les effets électrochimiques sont clairement séparés. Cette observation permet aussi des mesures de coefficient de diffusion, d'énergie d'ancrage, et d'effet flexoélectrique. Abstract. 2014 A hybrid nematic liquid crystal cell is a sensitive twisting power measuring device, since the homeotropic anchoring can be twisted without any torque. We observe the rotation of polarization for a light wave which propagates across such a hybrid nematic cell, doped with chiral ions. A DC electric field drags the ions inside or outside the optical twisting region of the hybrid cell. This results in a linear electrochiral effect. At large field, the quadratic effect from texture change and electrochemical effects are clearly separated. The diffusion constant, surface anchoring energy and flexoelectric constant are also measured.

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Chiral, Thermally Irreversible and Quasi‐Stealth Photochromic Dopant to Control Selective Reflection Wavelength of Cholesteric Liquid Crystal

et al. 2020

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A chiral and thermally irreversible photochromic fulgide derivative incorporating an (R)‐binaphthol unit in its acid anhydride moiety was used for the photoswitching of the pitch length of cholesteric liquid crystals. Since the absorption maximum wavelengths of both thermally stable photoisomers are nearly in the UV region (quasi‐stealth photochromism), it can be exposed to visible light without inducing photochromic reactions. Therefore, when the photoswitching molecule is added to a permanent cholesteric liquid crystal whose reflection light wavelength is in the visible region, the UV light‐induced photochromic reaction of the photoswitching molecule changes the wavelength of the reflection light in the visible light region. We have succeeded in regulating the color of cholesteric liquid crystalline cells between red and blue upon UV light irradiation. Attempts to introduce this system in polymer dispersed cholesteric liquid crystals are also described.

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Helical Twisting Power in Cholesteric Liquid Crystal Mixtures. I. Experimental Results

Cited by 25 publications

References 0 publications

Induction of chirality in nematic phases

Induction of chirality in nematic phases

Electrochiral effects in nematic liquid crystal-chiral salt mixtures

Chiral, Thermally Irreversible and Quasi‐Stealth Photochromic Dopant to Control Selective Reflection Wavelength of Cholesteric Liquid Crystal

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