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The recently discovered ferroelectric nematic (NF) liquid crystals (LCs) with over 0.04 C m−2 ferroelectric polarization and 104 relative dielectric constants, coupled with sub‐millisecond switching, offer potential applications in high‐power super capacitors and low voltage driven fast electro‐optical devices. This paper presents electrical, optical, and electro‐optical studies of a ferroelectric nematic LC material doped with commercially available chiral dopants. While the NF phase of the undoped LC is only monotropic, the chiral NF phase is enantiotropic, indicating a chirality induced stabilization of the polar nematic order. Compared to undoped NF material, a remarkable improvement of the electro‐optical switching time is demonstrated in the chiral doped materials. The color of the chiral mixtures that exhibit a selective reflection of visible light in the chiral NF phase, can be reversibly tuned by 0.02–0.1 V µm−1 in‐plane electric fields, which are much smaller than typically required in full‐color cholesteric LC displays and do not require complicated driving scheme. The fast switchable reflection color at low fields has potential applications for LC displays without backlight, smart windows, shutters, and e‐papers. [ABSTRACT FROM AUTHOR]

This paper clarifies the relationship between the molecular structures of chiral nematic liquid crystals and the shift in their reflection spectrum resulting from contact with volatile organic compounds (VOCs). We also propose a mechanism to explain the red- or blue-shift in the peak wavelength upon contact with VOC vapor. Furthermore, enhancement of the sensitivity of this method of VOC detection is discussed. [ABSTRACT FROM AUTHOR]

Homopolypeptide-based alignment media can induce different orientations of enantiomers as a result of their α-helical structures. This property enables the discrimination of enantiomers through anisotropic NMR parameters such as residual dipolar couplings (RDCs). In this paper, the enantiodiscriminating properties of two alignment media derived from polyglutamic acid derivatives - poly-γ-benzyl- L-glutamate (PBLG) and poly-γ-ethyl- L-glutamate (PELG) - are compared and discussed. The two analytes, isopinocampheol and β-pinene, are investigated, and the role of the lateral side chain of the homopolypeptide in the orientation process is examined. [ABSTRACT FROM AUTHOR]

Supramolecular chirality in a binary mixture of achiral bent-core (BC) and achiral rodlike mesogens was observed. Three different nanosegregated mesophases were determined in the binary system, and meaningful changes in circular dichroism (CD) were detected near the phase-transition temperatures of the rodlike mesogens. The highest CD intensity in the binary system was noted in the nanosegregated mesophase, in which the BC mesogens were in the helical nanofilament (HNF) phase and the rodlike mesogens were in the smectic A phase. The supramolecular chirality in the binary mixture was attributed to the self-assembled hierarchical chiral superstructures. Based on the experimental results, plausible scenarios for the chiral superstructures of the rodlike molecules embedded in the HNF networks are suggested. In addition, a system comprising BC and rodlike molecules doped with a photoresponsive compound exhibited remarkable photoswitching of CD intensity. According to the isothermal photoinduced phase transition of the embedded molecules in BC molecular HNFs, the observed CD intensities can be dynamically and reversibly modulated. Such a material with easily controllable functionality is of considerable interest in the field of materials science. [ABSTRACT FROM AUTHOR]

Residual dipolar couplings and other anisotropic NMR parameters are powerful tools for molecular structure elucidation when conventional techniques do not suffice. With current liquid crystalline preparations it is necessary to prepare two samples to extract isotropic and anisotropic data from spectra and to derive the residual dipolar couplings. Here, we present the preparation, measurement, and interpretation of a novel biphasic liquid crystalline phase where a single sample can be used to generate both isotropic and anisotropic data. First, we introduce the synthesis of the chiral polymer leading to the biphasic liquid crystal. Second, we present two approaches to measure spatially selective CLIP-HSQC spectra. From these spectra, we extracted the couplings, performed an assignment of diastereotopic protons, and achieved the enantiomeric discrimination of isopinocampheol as a well-studied test molecule. [ABSTRACT FROM AUTHOR]

Achiral stilbene polycatenars forming smectic, columnar or cubic phase depending on the terminal chains length, were studied. The cubic Im3m phase exhibited optical activity originating in twisted face-to-face molecular aggregates. The optical activity of the phase is preserved upon sample crystallization, providing evidence of a transfer of chirality on a molecular level. [ABSTRACT FROM AUTHOR]

We prepared a significant number of unsymmetrical liquid-crystalline dimers that exhibit the twist-bend nematic phase; a state of matter that exhibits spontaneous breaking of mirror symmetry and, for some materials, a microsecond electrooptic response. A number of novel unsymmetrical bimesogens were synthesized and in comparing their thermal behaviour to previous literature examples, we have uncovered an unexpected relationship between the thermal stability of the nematic and NTB phases. This relationship demonstrates that molecular shape dictates the incidence of this fascinating phase of matter and leads us to speculate as to the existence of 'twist-bend nematic phases' on length scales beyond those of the molecule. [ABSTRACT FROM AUTHOR]

Broadband terahertz (THz) chirality and wavefront manipulation play important roles in wireless communication, imaging, and radar systems. In this work, by integrating liquid crystal (LC) into a dielectric metasurface, the gradient phase distribution from the Si metasurface and the tunable birefringent phase shift from LC are engineered to perform an active spin‐decoupled beam steering with the strong spin asymmetric transmission. By using geometric symmetry analysis, the relationships between the symmetry breaking and the optical chirality of the metadevice are revealed under different LC orientations, and both the simulations and experiments further verify the dependence of this chirality on spin‐decoupled beam steering with different spin states. The results show that with the orientation changes of the LC by driving the different magnetic fields, the circular dichroism of the device at the 0° deflection angle is ≈100% dynamically modulated and even flipped in the broadband range of 0.8–1.3 THz. With these changes in THz chirality, a tunable spin‐decoupled beam steering occurs in the range of 25°‐45°. This work shows that tunable LC anisotropy leads to more complex symmetry breaking in this structure, and results in more functions than conventional spin‐decoupled wavefront manipulations, which expands the scope of THz chiral metadevice and its applications. [ABSTRACT FROM AUTHOR]

The Front Cover demonstrate the photocontrol of selective reflection colors that originate from the self‐organized helical structure of chiral nematic liquid crystals (N*LCs) by using closed‐/open‐type dopants. The drastic structure changes of the dopants by light stimuli enable reversible broad‐spectrum control of selective reflections of N*LCs with opposite helical sign. In their Full Paper, H. Nishikawa et al. focus on reversible broad‐spectrum control of selective reflections of opposite‐handed chiral nematics by using new chiral dopants. More information can be found in the Full Paper by H. Nishikawa et al. on page 710 in Issue 6, 2017 (DOI: 10.1002/open.201700121). [ABSTRACT FROM AUTHOR]

Chirality represents a fundamental structure in nature and the induction and reversible modulation of supramolecular chirality with feasible techniques is of great value in the design of new chiroptical smart materials. Herein, two kinds of azobenzene side‐chain polymers (without spacer: Azo‐PMA0; with 6 spacers: Azo‐PMA6) are synthesized, the length of spacer and azobenzene chromophores play a vital role in chirality transfer and modulation. The supramolecular chiral arrangement of Azo‐PMA0 (amorphous phase) can be completely controlled and reversibly modulated over multiple cycles by 450 nm circularly polarized light driven by the supramolecular interaction between azo groups of polymer chains, with an absorption dissymmetry factor (g) value of 0.0019. The chiroptical properties of Azo‐PMA6 (liquid crystal state) can also be reversibly modulated by UV light and thermal annealing treatment during trans‐cis isomerization of azo chromophore, with the g‐value changes from 0–0.038. The successful construction of reversible chiral induction and modulation based on side chain azobenzene polymers may pave the way for designing photo‐switchable functional materials. [ABSTRACT FROM AUTHOR]

Cover Feature: Stabilization of Bicontinuous Cubic Phase and Its Two-Sided Nature Produced by Use of Siloxane Tails and Introduction of Molecular Nonsymmetry (Chem. Eur. J. 40/2021) Keywords: chirality; cubic phases; liquid crystals; soft matter EN chirality cubic phases liquid crystals soft matter 10213 10213 1 07/19/21 20210716 NES 210716 B The "two-sided nature" b of the I Ia i 3 I d i gyroid-type bicontinuous cubic liquid crystalline (Cub SB bi sb LC) phase of a nonsymmetric core molecule is depicted in the cover image. Two core assembly modes specific to each symmetric molecule with larger naphthalene or smaller benzene cores appear to form the three-dimensional helical network, depending on temperature and thermal cycle. [Extracted from the article]

A recent intriguing finding that a helical network arrangement forms the bicontinuous cubic phase is attracting great attention for the possibility of new routes to asymmetric synthesis by achiral molecules. However, the design of the molecular structure for the cubic phase is still unrevealed. In this work, a nonsymmetric core molecule with larger naphthalene and smaller benzene moieties at each side of the central linkage and the same disiloxanyldecyloxy terminal at both terminals is shown to be the first example of molecule forming both single‐layered and double‐layered core assembly modes in the Ia3d phase as a single molecule system. The molecule forms the former mode at high temperatures as a thermodynamically stable phase, similarly to the symmetric naphthalene core system, whereas, on cooling below a temperature (∼350 K), a metastable Ia3d phase forms a double‐layered core state down to room temperature, which is common to the benzene core system. As another effect of the nonsymmetric core, the cubic phase is maintained at room temperature for more than 100 days with slight distortion. Infrared spectral studies and quantum chemical calculations suggested the easy transformation between the two core assembly modes. The core nonsymmetry can be a versatile fine‐tuning of the core assembly mode and phase stability for the cubic phase molecules. [ABSTRACT FROM AUTHOR]

The ability of a star‐shaped tris(triazolyl)triazine derivative to hierarchically build supramolecular chiral columnar organizations through the formation of H‐bonded complexes with benzoic acids was studied from a theoretical and experimental point of view. The combined study has been done at three different levels including the study of the structure of the triazine core, the association with benzoic acids in stoichiometry 1:3, and the assembly of 1:3 complexes in helical aggregates. Although the star‐shaped triazine core crystallizes in a non‐C3 conformation, the C3‐symmetric conformation is theoretically predicted to be more stable and gives rise to a favorable C3 supramolecular 1:3 complex upon the interaction with three benzoic acids in their voids. In addition, calculations at different levels (DFT, PM7, and MM3) for the 1:3 host‐guest complex predict the formation of large stable columnar helical aggregates stabilized by the compact packing of the interstitial acids by π–π and CH⋅⋅⋅π interactions. The acids restrict the movement of the the star‐shaped triazine cores along the stacking axis causing a template effect in the self‐assembly of the complex. Theoretical predictions correlate with experimental results, since the interaction with achiral or chiral 3,4,5‐(4‐alkoxybenzyloxy)benzoic acids gives rise to supramolecular complexes that organize in bulk hexagonal columnar mesophases stable at room temperature with intracolumnar order. The existence of supramolecular chirality in the mesophase was determined for complexes formed by acids derived from (S)‐2‐octanol. Chiral aggregation was also evidenced for complexes formed in dodecane. [ABSTRACT FROM AUTHOR]

Cover Feature: Stereochemical Rules Govern the Soft Self-Assembly of Achiral Compounds: Understanding the Heliconical Liquid-Crystalline Phases of Bent-Core Mesogens (Chem. Eur. J. 21/2020) Keywords: chirality; de Vries phases; ferroelectricity; helical structures; liquid crystals EN chirality de Vries phases ferroelectricity helical structures liquid crystals 4641 4641 1 04/10/20 20200409 NES 200409 B Spontaneous double mirror symmetry breaking in anisotropic polar fluids b is observed in the lamellar liquid crystalline phases of the shown achiral bent-core molecules, where two distinct modes of supramolecular chirality develop simultaneously. Chirality, de Vries phases, ferroelectricity, helical structures, liquid crystals. [Extracted from the article]

We describe two parallel pathways for enhancing the intrinsic photoluminescence of an organic emitter dispersed in a liquid crystal (LC) medium. The pathways have independent origins: (i) Metal enhanced fluorescence (MEF) incorporating gold nanoparticles having an organic shell of pro‐mesogenic cholesterol esters; and (ii) Matching the photonic band gap (PBG) due to the helical structure in a self‐assembled chiral system with the excitation wavelength. This unprecedented combination of both pathways achieves a level of photoluminescence exceeding the sum of the contribution from the individual methods. This conjunctive protocol results in an overall enhancement by a factor of 37 between the emitter dispersed in a non‐chiral LC and that appealing to both MEF and PBG pathways. Circular polarized luminescence measurements also show that this protocol helps in effective discrimination of chiral light achieving a large dissymmetry factor whose magnitude (+0.33) is comparable to the highest recorded to date. Electric field switching between two states is also shown to result in appreciable fluorescence modulation. Being generic in nature the protocol employed can be adapted to a variety of situations with the large magnitude as well the modulation level suitable for applications such as biosensors, various analyte detection, and other photonic devices. [ABSTRACT FROM AUTHOR]

Abstract: The influence of photoinduced isomerization on the enantiomeric separation of two newly synthesized liquid crystalline materials, liquid crystals 1 and 2, was studied by high‐performance liquid chromatography on a chiral stationary phase Chiralpack AD‐3. Both materials have one chiral center and one diazene moiety. The compounds were separated into their E and Z isomeric forms. The conditions and time scale of the ultraviolet‐induced E to Z transition were briefly evaluated. Under the optimized conditions, we were able to baseline separate the S and R enantiomers of both the studied materials in their E isomeric form. The chiral separation of liquid crystal 2 after ultraviolet irradiation was unsuccessful. In contrast, the chiral separation of liquid crystal 1 possessing a similar structure to liquid crystal 2 provided baseline separation in its Z isomeric form as well. Previously, we have shown the influence of photoinduced isomerization and its utilization in the enantioseparation on relatively simple molecules. Here, we demonstrate that (1) much more complex compounds can also be successfully separated despite the bulkiness of the achiral part of the structure and (2) photoinduced isomerization even for such complex molecules still strongly influences their chromatographic properties. [ABSTRACT FROM AUTHOR]

ABSTRACT: Polymerization of crosslinkable liquid crystal monomers in chiral liquid crystalline media stabilizes the phase and enables distinct electro‐optic properties relative to small‐molecule analogs. Particularly interesting are cases where the polymerization forms a crosslinked polymer network that maintains a “structural” chirality. Recent reports have employed this methodology to realize a diverse set of electro‐optic responses in polymer stabilized cholesteric liquid crystals (PSCLCs) including reflection bandwidth broadening, reflection wavelength tuning, and dynamic scattering modes. It has been proposed that the mechanism at the root of these electro‐optic responses is an ion‐mediated, electromechanical deformation of the stabilizing and structurally chiral polymer network. In an effort to better understand the nature of these deformations, here we have characterized the electro‐optic response of PSCLCs with different polymer concentrations and crosslink densities. The dynamic response of PSCLCs to electric fields exhibits a time‐dependent behavior reminiscent of the creep of polymeric materials to mechanical deformations. The electro‐optic response can be described as the superposition of two contributions: the fast deformation of a relatively soft component of the polymer network (1–2 s) and the slower (10–20 s) deformation of a harder component. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1087–1093 [ABSTRACT FROM AUTHOR]

We demonstrate reversible RGB-color photocontrol of a chiral nematic liquid crystal (N*LC) by using newly synthesized closed- and open-type chiral dopants. The photoswitching elements in the dopants are azobenzene units on axially chiral binaphthyl cores. Owing to cis- trans photoisomerization of the azobenzene units, both closed- and open-type compounds showed higher solubility, larger helical twisting power (HTP), and larger changes in HTP than conventional chiral dopants in host LCs. Thus, even at very low dopant concentrations, we successfully controlled the chirality of the induced helical structure of the N*LCs. Consequently, the N*LCs reflected right- and left-handed circularly polarized light (CPL) under a light stimulus. In the N*LCs with closed-type chiral dopants, the RGB-color reflection was reversibly controlled within several seconds. Interestingly, the open-type chiral dopant reversibly inverted CPL with opposite handedness in the near and short-wave IR regions. These novel materials are expected to realize new applications and perspectives in color information and similar technologies. [ABSTRACT FROM AUTHOR]

A moderately concentrated solution of a helically chiral polyisonitrile forms a stable two‐phase system in CDCl3 with the dense phase being close to isotropic and the less dense layer forming a completely anisotropic lyotropic liquid crystalline phase. This enables the enantiodifferentiating measurement of isotropic and anisotropic NMR parameters from a single sample by novel spatially resolved NMR methods. More information can be found in the Full Paper by M. Reggelin, B. Luy et al. on page 13351. [ABSTRACT FROM AUTHOR]

Spontaneous mirror-symmetry breaking is a fundamental process for development of chirality in natural and in artificial self-assembled systems. A series of triple chain azobenzene based rod-like compounds is investigated that show mirror-symmetry breaking in an isotropic liquid occurring adjacent to a lamellar LC phase. The transition between the lamellar phase and the symmetry-broken liquid is affected by trans- cis photoisomerization, which allows a fast and reversible photoinduced switching between chiral and achiral states with non-polarized light. [ABSTRACT FROM AUTHOR]

The twist-bend nematic (NTB) phase is a recently discovered liquid-crystalline phase that exhibits macroscopic chirality even when formed from achiral materials, and as such presents a unique testbed for studies concerning the spontaneous breaking of mirror symmetry in soft matter. It is primarily exhibited by materials for which the molecular structure is composed of two rigid aromatic units (such as biphenyl connected by a flexible spacer). The local structure of the NTB phase is nematic-like-with molecules having an average orientational order but no positional order-with a nanoscale helix in which the pitch (i.e., the repeat distance of the helix) is of the order of several nanometres. A helix is chiral, and so the bulk NTB phase-in the absence of a biasing chiral environment-spontaneously separates into macroscopic domains of opposite handedness. After discussing the structure of this mesophase and its elucidation, this concept article presents the molecular factors that determine its incidence. The apparent dependency primarily on molecular shape and bend angle rather than particular functional group combinations manifests in this mesophase being exhibited on length scales far beyond those of simple liquid-crystalline dimers, not only in oligomers and polymers, but also in aqueous suspensions of micron sized helical particles. [ABSTRACT FROM AUTHOR]

Structural chemistry began with Louis Pasteur, who first saw the configuration of molecules manifest in the shapes of crystals. Here is reviewed forgotten, century-old efforts to make molecular configuration vivid in polycrystalline ensembles. Resorcinol, and a variety of other simple molecular crystals, when grown from the melt in the presence of resolved chiral additives, such as tartaric acids, form spectacular bull's-eye patterns evident in the petrographic microscope. Concentric, rhythmic optical bands in so-called banded spherulites are tell-tale signs of the twisting of helicoidal crystalline lamellae. The sense of twisting was assayed by correlating displacements of extinction bands on rotation with additive configurations. Thus, the arrangements of atoms in space were made manifest in crystal form - not in the appearance of hemihedral facets, but rather, in the chirality of nonclassical morphologies with Gaussian curvature. The far reaching consequences of these experiments for molecular crystal growth and form, long ago foreseen, are evaluated with the hindsight of an extra century of experience and sophistication. The narrative aims to draw a continuous thread through the work of Pasteur, Grigorii Vyroubov, Frédéric Wallerant, John Monteath Robertson, Hélène Metzger, and Jack Dunitz. [ABSTRACT FROM AUTHOR]

The reconstruction capability of the blue phase (BP) template with low polymer concentration was investigated. A threshold polymer concentration to reconstruct the BP with the chiral three-dimensional template was confirmed in different kinds of polymer systems. The anchoring energy of the template may reassemble the double twist cylinder structure of BP liquid crystal (BPLC) by refilling either the same-handed or reverse-handed chiral materials within a certain range of helical twisting power (HTP). Meanwhile, because of the lowered anchoring energy, the kerr constant of the reconstructed BPLC increased by 104%, from 1.81 nm/V2 to 3.70 nm/V2, by refilling the reverse-handed chiral material. [ABSTRACT FROM AUTHOR]

Two isomeric achiral bent-core liquid crystals involving a 4-cyanoresorcinol core and containing a carbosilane unit as nanosegregating segment were synthesized and were shown to form ferroelectric liquid-crystalline phases. Inversion of the direction of one of the COO groups in these molecules leads to a distinct distribution of the electrostatic potential along the surface of the molecule and to a strong change of the molecular dipole moments. Thus, a distinct degree of segregation of the carbosilane units and consequent modification of the phase structure and coherence length of polar order result. For the compound with larger dipole moment ( CN1) segregation of the carbosilane units is suppressed, and this compound forms paraelectric SmA and SmC phases; polar order is only achieved after transition to a new LC phase, namely, the ferroelectric leaning phase (SmCLsPS) with the unique feature that tilt direction and polar direction coincide. The isomeric compound CN2 with a smaller dipole moment forms separate layers of the carbosilane groups and shows a randomized polar SmA phase (SmAPAR) and ferroelectric polydomain SmCsPS phases with orthogonal combination of tilt and polar direction and much higher polarizations. Thus, surprisingly, the compound with the smaller molecular dipole moment shows increased polar order in the LC phases. Besides ferroelectricity, mirror-symmetry breaking with formation of a conglomerate of macroscopic chiral domains was observed in one of the SmC phases of CN1. These investigations contribute to the general understanding of the development of polar order and chirality in soft matter. [ABSTRACT FROM AUTHOR]

New chiral dimers consisting of a rod-like and cholesterol mesogenic units are reported to form a chiral twist-bend nematic phase (NTB*) with heliconical structure. The compressibility of the NTB phase made of bent dimers was found to be as large as in smectic phases, which is consistent with the nanoperiodic structure of the NTB phase. The atomic force microscopy observations in chiral bent dimers revealed a periodicity of about 50 nm, which is significantly larger than the one reported previously for non-chiral compounds (ca. 10 nm). [ABSTRACT FROM AUTHOR]

Three rationally designed axially chiral diarylethene switches were synthesized and their application as chiral dopants for phototunable cholesteric liquid crystal devices was investigated. Design of these molecules was based on the combination of photochromic dithienylcyclopentene core with bridged binaphthyl units as chiral precursors. Aromatic groups were introduced to the molecules at 6,6′-positions of binaphthyls through a Suzuki-Miyaura coupling reaction. Their helical twisting powers (HTPs) are significantly higher than those of the known chiral diarylethenes reported as chiral dopants so far. Photocyclization of these molecules upon light irradiation brought out dramatic variation in HTPs between different states. The primary colors, red, green, and blue, were obtained in reflection on light irradiation and with thermal stability. Moreover, a multi-switchable photodisplay was demonstrated using one of these chiral molecular switches. [ABSTRACT FROM AUTHOR]

The orientations of liquid crystals (LCs) anchored on monolayers formed from mixtures of chiral versus achiral molecules were compared. Changes in the enantiomeric excess of mixed monolayers of chiral dipeptides gave rise to continuous changes in the orientations of nematic LCs, allowing arbitrary tuning of the azimuthal orientations of LCs over a range of 100°. In contrast, the same LCs exhibited discontinuous changes in orientation on surfaces presenting mixtures of achiral molecules. These striking differences in the anchoring of LCs on surfaces presenting chiral versus achiral molecules provide insights into the molecular origins of ordering transitions of LCs, and provide new principles based on chiral monolayers for the rational design of surfaces that permit continuous tuning of the orientations of LCs. [ABSTRACT FROM AUTHOR]

A ribbon-shaped chiral liquid crystalline (LC) dendrimer with photochromic azobenzene mesogens and an isosorbide chiral center (abbreviated as AZ3DLC) was successfully synthesized and its major phase transitions were studied by using differential scanning calorimetry (DSC) and linear polarized optical microscopy (POM). Its ordered structures at different temperatures were further identified through structure-sensitive diffraction techniques. Based on the experimental results, it was found that the AZ3DLC molecule exhibited the low-ordered chiral smectic (Sm*) LC phase with 6.31 nm periodicity at a high-temperature phase region. AZ3DLC showed the reversible photoisomerization in both organic solvents and nematic (N) LC media. As a chiral-inducing agent, it exhibited a good solubility, a high helical-twisting power, and a large change in the helical-twisting power due to its photochemical isomerization in the commercially available N LC hosts. Therefore, we were able to reversibly 'remote-control' the colors in the whole visible region by finely tuning the helical pitch of the spontaneously formed helical superstructures. [ABSTRACT FROM AUTHOR]

Successful alignment control of the B4 helical nanofilament assembly in a binary mixture system of bent-shaped and rod-shaped liquid crystals is demonstrated. The aligned nanofilament domains appear as extremely smooth and uniform stripes over millimeters. The interferometric second-harmonic generation microscopy technique is developed and applied to these aligned domains. It is found that not only chirality, but also polarity, are preserved in a single domain formed from a single nucleus. Such an easily processed uniform bulk of the spontaneously symmetry-broken material is intriguing in functional materials science. [ABSTRACT FROM AUTHOR]

The article presents a study which examines a general method which is based on a nematic (N) phase and applicable for compounds without N phase but exhibit helical nanofilament (HNF) B4 phase. It states that to confirm deracemization occurrence in the Bx phase, circular dichroism (CD) measurements were performed. It concludes that a high excess of homochiral HNF domains in the Bx phase from a N-Bx phase sequence mixture was obtained by cooling twisted nematic (TN) cells.

Herein we report a group of five planar chiral molecules as photon-mode chiral switches for the reversible control of the self-assembled superstructures of doped chiral nematic liquid crystals. The chiral switches are composed of an asymmetrically substituted aromatic moiety and a photoisomerizing azobenzene unit connected in a cyclic manner through methylene spacers of varying lengths. All the molecules show conformational restriction in the rotation of the asymmetrically substituted aromatic moiety in both the E and Z states of the azobenzene units resulting in planar chirality with separable enantiomers. Our newly synthesized compounds in pure enantiomeric form show high helical twisting power (HTP) in addition to an improved change in HTP between the E and Z states. The molecule with a diphenylnaphthalene unit shows the highest ever known initial helical twisting power among chiral dopants with planar chirality. In addition to the reversible tuning of reflection colors, we employed the enantiomers of these five compounds in combination with four nematic liquid crystalline hosts to study their properties as molecular machines; the change in HTP of the chiral dopant upon photoisomerization induces rotation of the texture of the liquid crystal surfaces. Importantly, this study has revealed a linear dependence of the ratio of the difference between HTPs before and after irradiation against the absolute value of the initial HTP, not the absolute value of the change in helical twisting power between two states, on the angle of rotation of micro-objects on chiral nematic liquid crystalline films. This study has also revealed that a change in irradiation intensity does not affect the maximum angle of rotation, but it does affect the speed of rotational reorganization of the cholesteric helix. [ABSTRACT FROM AUTHOR]

Chiral supramolecular assemblies are abundant in nature, but controlling the chirality of artificial systems still remains a challenge. In this work, we developed a system where supramolecular chirality can be controlled between chiral and achiral states, namely a chiral "1/0" switch using a flower‐like azobenzene compound with a binaphthol core. Upon photoisomerization by ultraviolet irradiation, the terminal alkyl tails envelop the chiral "centre" with a reduction in the dihedral angle of the binaphthol moiety from 76.1° to 61.4°, like "closing petals". In the doped liquid crystal E7 matrix, this hierarchical conformational transition prevents the transfer of chirality to the host liquid crystal, resulting in a degradation from cholesteric phase (HTP value: 13.84 μm−1) to an achiral nematic phase. [ABSTRACT FROM AUTHOR]