Chiral Liquid Research Articles

Synthesis and Characterization of Asymmetric Azatwistarenes with Chiroptical Property.

Three novel azatwistarenes 5a, 8, and 13 have been synthesized via the Povarov reaction and fully characterized. All of the enantiomers were separated using chiral high-performance liquid chromatography, and their optical properties were investigated through circular dichroism and circularly polarized luminescence spectra. In addition, such desired azatwistarenes have a positive response to acid in dichloromethane.

Flowing Liquid Crystal Torons Around Obstacles

Liquid crystal torons, localized topological structures, are known for their stability and dynamic behaviour in response to external stimuli, making them attractive for advanced material applications. In this study, we investigate the flow of torons in chiral nematic liquid crystals around obstacles. We simulate the fluid flow and director field interactions using a hybrid numerical method combining lattice Boltzmann and finite difference techniques. Our results reveal that the toron dynamical behaviour depends strongly on the impact parameter from the obstacle. At impact parameters smaller than half cholesteric pitch, the flowing toron is destabilized by the interaction with the obstacle; otherwise, the flowing toron follows a trajectory with a deflection which decays exponentially with the impact parameter. Additionally, we explore the scattering of torons by multiple obstacles, providing insights into how the dynamics of these structures respond to complex environments.

A chiral supramolecular liquid crystal based on pillararene and its application in information encryption.

A chiral supramolecular liquid crystal based on a pillararene mesogen was constructed. The regulation of liquid crystal behavior was achieved through the host-guest interactions between the pillararene-based mesogen and a tetraphenylethylene-containing guest. In addition, this supramolecular liquid crystal system, showing pH-responsive fluorescence emission character, was applied as an information encryption material capable of storing multiple levels of distinct information, thereby enriching the application of liquid crystal materials in the field of information security.

Enhancing Color Gamut with Wavelength‐Selective Polarization Modulation in Chiral Liquid Crystals

Enhancing Color Gamut with Wavelength‐Selective Polarization Modulation in Chiral Liquid Crystals

Widely tunable reflection by a hybrid ion-doped positive-negative chiral nematic liquid crystal under an electric field.

In this study, a new methodology, in which the cation and chiral agent are doped in positive and negative nematic liquid crystal mixture to form cation-doped positive-negative chiral nematic liquid crystals (PN-CNLCs), is proposed. These PN-CNLCs are capable of achieving a wide wavelength tuning range close to 90 nm under the action of a high-frequency electric field. The dielectric interaction between these two liquid crystals with different dielectric anisotropies in the electric field allows for the effective change of the pitch of the CLCs. We discovered the tilting of the pitch in the PN-CNLCs by a series of well-designed validation experiments. The experimental results prove the symmetrical helix is formed along the alignment direction in PN-CNLCs. Furthermore, the experiments demonstrated that an increase in voltage does not directly affect the pitch, but it increases the tilt angle of the helix axis with respect to the normal of the LC cell. This study offers, to our knowledge, a novel perspective on the tuning performance of CLCs under electric field conditions, by integrating the properties of positive and negative liquid crystals. This finding not only contributes to the understanding of the electric field response mechanism of CLCs but also provides new avenues for the application of CLCs in fields such as wavelength tuning.

Self‐Assembled Biconvex Microlens Array Using Chiral Ferroelectric Nematic Liquid Crystals

AbstractRecently, it is shown (Popov et al, Sci. Rep, 2017, 7, 1603) that chiral nematic liquid crystal films adopt biconvex lens shapes underwater, which may explain the formation of insect eyes, but restrict their practical application. Here it is demonstrated that chiral ferroelectric nematic liquid crystals, where the ferroelectric polarization aligns parallel to the air interface, can spontaneously form biconvex lens arrays in air when suspended in submillimeter‐size grids. Using Digital Holographic Microscopy, it is shown that the lens has a paraboloid shape and the curvature radius at the center decreases with increasing chiral dopant concentration, i.e., with decreasing helical pitch. Simultaneous measurements of the imaging properties of the lenses show the focal length depends on the pitch, thus offering tunability. The physical mechanism of formation of the self‐assembled ferroelectric nematic microlenses is also discussed.

Electrically Tunable Chiral Ferroelectric Nematic Liquid Crystal Reflectors

AbstractManipulating light is an important area of optical research and development. To that end, tunable dichroic devices in which the reflectivity at differing wavelengths can be adjusted, are particularly valuable. This work is motivated by recent studies of the optical properties of chiral ferroelectric nematic liquid crystals (FNLCs). Here electro‐optical studies are presented on two room temperature, FNLC materials that demonstrate electrically tunable reflectivity when subject to a field below 0.2 V µm−1. Moreover, under appropriate conditions, the reflectivity can also be electrically (and reversibly) tuned (without change of color) from 0% to 40%. Reversible, low voltage tunable mirrors, having miniscule power consumption and operable around ambient temperature are expected to be useful in diverse applications ranging from energy‐saving, smart windows to virtual reality interfaces.

Induced blue phase and twist grain boundary phase in binary mixtures of chiral calamitic and achiral hockey stick-shaped liquid crystals

Frustrated phases in chiral liquid crystalline systems, such as the blue phase (BP) and the twist grain boundary (TGB) phase, can create new opportunities in liquid crystal research. These frustrated phases have unique optical properties which can be used for specific applications. A new binary mixture system composed of a chiral rod-like ferroelectric liquid crystal and an achiral hockey stick-shaped compound was designed. This binary system exhibits induced frustration, resulting in the emergence of the BP-III and TGB*A phases in addition to the chiral ferroelectric Smectic-C* phase. We report a comprehensive study on several binary mixtures (xH-22.5= 0.162, 0.25, 0.396, 0.562) designed of a chiral ferroelectric liquid crystal derived from the lactic acid, namely 4-(octyloxy)phenyl 3-methoxy-4-((4-((2-(pentyloxy)­propanoyl)­oxy)benzoyl)oxybenzoate and achiral hockey stick-shaped compound, namely (E)-4-((E-((3-(decyloxy)-2-methylphenyl)imino)methyl)-phenyl 3-(4-(dodecyloxy)phenyl)acrylate. These mixtures induced the blue phase (BP-III, ~2.5–6.2K) and the twist grain boundary Smectic-A*phase (TGB*A  ~1.8–6K). Polarizing optical microscopy, birefringence, and dielectric spectroscopy were employed to investigate the BP-III and  phases, as those techniques provide insights into their structural and dynamic properties. The ferroelectric behaviour of the SmC* mesophase was investigated by electro-optics. The obtained results are discussed in relation to the molecular structures of the used materials.

Supramolecular Arrangement and Conformational and Dynamic Properties of Chiral Smectic Liquid Crystals Obtained through Nuclear Magnetic Resonance: A Brief Review

Ferroelectric and antiferroelectric smectic liquid crystalline (LC) phases are still at the center of investigations and interests for both their fundamental properties and variety of technological applications. This review aims to report the main contributions based on different nuclear magnetic resonance (NMR) techniques to the study of chiral liquid crystalline calamitic mesogens forming smectic phases, such as the SmA, the SmC* (ferroelectric), and the SmC*A (antiferroelectric) phases. 2H NMR and 13C NMR techniques and their combination were of help in clarifying the local orientational properties (i.e., the molecular and fragments’ main orientational order parameters) at the transition between the SmA and the SmC* phases, and in the particular case of de Vries liquid crystals, NMR studies gave important clues regarding the actual models describing the molecular arrangement in these two phases formed by de Vries LCs. Moreover, this review describes how the combination of 2H NMR relaxation times’ analysis, 1H NMR relaxometry, and 1H NMR diffusometry was successfully applied to the study of chiral smectogens forming the SmC* and SmC*A phases, with the determination of relevant parameters describing both rotational molecular and internal motions, collective dynamics, and translational self-diffusion motions. Several cases will be reported concerning NMR investigations of chiral ferroelectric and antiferroelectric phases, underlining the great potential of combined NMR approaches to the study of supramolecular, conformational, and dynamic properties of liquid crystals.

Topologically frustrated structures in inkjet printed chiral nematic liquid crystal droplets - experiments and simulations.

Director field alignment in inkjet printed droplets of chiral nematic liquid crystalline materials is investigated using both experiments and numerical simulations. Experimental investigations are performed by depositing droplets of varying sizes and pitches on homeotropic alignment layers. The competition between the bulk behaviour of the chiral nematic liquid crystal and the boundary conditions imposed by the droplet surface leads to the formation of a range of possible internal director configurations. Numerical investigations are performed using a free energy minimisation approach, and the resultant simulated polarising optical microscope images are found to agree well with experimental observations.

Comparative computational analysis of orthoconic antiferroelectric liquid crystals: DFT analysis.

The study undertakes a comparative analysis of four distinct semi-fluorinated chiral Organic Active Ferroelectric Liquid Crystals (OAFLCs). The comparative analysis of the compounds is done by using various parameters, including thermodynamic, non-linear optical, electrical, atomic charge distribution, and atomic orientations. We use optimization algorithms to look at chemical reactivity, electrical properties, intermolecular interactions, and static hyperpolarizability. Sample 4 is the best choice for a wide range of display applications. This research contributes to understanding the nuanced properties of semi-fluorinated chiral OAFLCs and highlights Sample 4's potential for novel applications in display technology, owing to its superior stability and optimized properties. This study helps to enhance our understanding of the comparative analysis of semi-fluorinated chiral OAFLCs for potential advancements in display technologies by incorporating findings from key studies. The simulations are performed using density functional theory (DFT) with the B3LYP functional for predicting molecular properties, and Vibrational Energy Distribution Analysis (VEDA) software is used to perform the vibrational analysis of the molecules.

Density-density correlation functions of chiral Luttinger liquids with a point-contact impurity

The density-density correlation functions (most singular parts) of chiral Luttinger liquids forming the fractional quantum Hall effect (FQHE) edge are systematically derived in presence of a point-contact junction acting as a localised scalar impurity and are shown to be expressible as compact analytical functions with second order poles and involving the bare scale-independent reflection and transmission coefficients. The results are validated on comparison with standard fermionic perturbation theory. The linear response Hall conductance in the absence of a point-contact is recovered from the obtained density-density correlation functions (DDCF). The system under consideration is inhomogeneous with broken translational invariance and for such systems in one dimension, the connected moments of the density fluctuation operator beyond second order need not be included in order to retrieve the most singular parts of the correlations. The reason being that all odd moments of the density are zero and all higher order even moments are less singular than the quadratic moment. The implications of these results when used in conjunction with bosonization methods in presence of impurity backscattering is briefly discussed.

Exploring the Effects of Optically Active Solvents in Chiral Chromatography on Polysaccharide-Based Columns.

Exploring the effectiveness of optically active solvents as mobile-phase modifiers in chiral liquid chromatography (LC) can offer an additional new tool to tune the chiral selectivity. Hence, the potential of l-ethyl lactate (LEL), a biobased solvent of this nature, was explored for its distinctive interactions with both the mobile phase and analytes, as anticipated from its chiral nature. The findings reveal that LEL provides distinct selectivity compared to commonly used modifiers in chiral LC. Reversed-phase LC (RPLC)-type chiral separations were therefore compared under various conditions whereby LEL was partially or completely replacing common achiral solvents such as acetonitrile (ACN) and methanol (MeOH). An increase in chiral resolution was obtained in 8 of 16 test compounds. For 5 of them a decrease was obtained, and 3 test solutes did not offer satisfactory results under any of the tested conditions on the polysaccharide columns. When LEL was combined with methanol instead of ACN, worse results were obtained, presumably due to its protic nature. Moreover, LEL demonstrates excellent compatibility with salt additives and is fully miscible with aqueous phases. Interestingly, a steeper increase in chiral resolution is observed for LEL, as compared to ACN at lower temperatures. While LEL is somewhat hindered by its higher UV absorbance, it paves the way toward more simplified chiral screening platforms, whereby chiral solutions can be found for fewer columns and greener solvents such as LEL are incorporated. Finally, to elucidate the impact of chiral interactions between the solvent and analytes, the influence of d-ethyl lactate (DEL) was compared with that of LEL. The results revealed different interactions between the stereoisomers of ethyl lactate (EL) and chiral analytes, demonstrating an influence of optically active solvents on enantioseparations.

Blue Phase III from Bent-Core Liquid Crystals: Unveiling Thermal Stability & Unique Traits - A Comprehensive Review.

This review article mainly delves into the comprehensive development, thermal stabilization, characteristics, and applications of Blue Phase III (BPIII) derived from non-calamitic, mainly T-shaped and bent-core liquid crystals (BCLC). The discussion begins with discovering and characterizing various liquid crystal (LC) phases of BCLCs, emphasizing the significance of the nematic (N) phase in three and four-ring BCLCs. Following this, the focus shifts to the stabilization, properties, and potential applications of BPIII, particularly those derived from non-conventionalliquid crystals. The review highlights the exceptional electro-optical (E-O) properties of BPIII, including high Kerr constants and distinct phase transitions. Studies reveal the impact of chirality on thermal behavior, microscopic observations, and the influence of molecular structures on mesophase formation. Investigations into asymmetrical chiral liquid crystal diads and hydrogen-bonded complexes underscore the importance of molecular design in expanding BPIII ranges. Furthermore, achiral unsymmetrical BCLC designs reveal significant insights into the interplay between molecular structure, phase transitions, and E-O behavior.Additionally, the structural transformation and E-O properties of highly polar BCLCs are examined to stabilize BPIII at room temperature, achieving notable Kerr constants and low voltage requirements. These collective studies provide a thorough understanding of BPIII and its promising applications in materials science and technology.

From Chitin Nanowhisker Colloidal Dispersions to Anisotropic Microfibers: Structural Evolution in Its Transformation Process as Revealed by Synchrotron Wide-Angle X-ray Diffraction Measurements.

Nanowhiskers in a colloidal dispersion are known to form chiral nematic liquid crystals (CNLC), as seen in a cellulose nanowhisker or so-called cellulose nanocrystal and chitin nanowhisker. In our related work, we clarified that once the thus-created chitin nanowhiskers with surface modified by chitosan (CTWK-CS) in CNLC phase were wet-spun, we could directly obtain anisotropic microfibers containing the highly ordered CTWK-CS. This drastic structural transformation from CNLC to anisotropic microfibers might relate to several important stages, i.e., stage (i) is the alignment of CTWK-CS initiated by a specific concentration and flow to create aggregation in the CNLC state, stage (ii) is the coagulation of CTWK-CS in CNLC to transform to microfibers, and stage (iii) is the drying of the thus-extruded microfibers to allow CTWK-CS alignment. The present work sets up the experimental systems simulating stages (i) and (iii) to reveal the orientational behavior of CTWK-CS and the structural evolution, respectively, by synchrotron 2D WAXD measurement. In stage (i), the high degree of the parallel alignments of CTWK-CS with the chain axis oriented along the flow direction of the colloidal dispersions confirms that the flow and concentration synergistically controlled CTWK-CS alignment. In contrast, for stage (iii), the poor c-axial orientation of CTWK-CS in as-spun wet microfibers gradually changed to the high degree of c-axial orientation along the fiber direction during drying process, indicating a reorientation of CTWK-CS along with dehydration. The present study declares an in situ observation of the direct wet spinning of nanowhiskers about their remarkable alignments in the sheared colloidal dispersions (stage (i)) and their random-to-high reorientation during the drying process of the as-spun wet microfiber (stage (iii)).

Chiral liquid crystals based on pillararene and supramolecular self-assembly-induced chirality amplification

Chiral liquid crystals based on pillararene and supramolecular self-assembly-induced chirality amplification

Chiral liquid crystal dimers with smectic phases for stabilization of anticlinic state in surface-stabilised geometry

The growing demand for enhanced optical quality and faster electro-optical response in liquid crystal (LC) photonic devices has expanded the search for advanced materials capable of improving the properties of LCs beyond conventional ones. Among these compounds are LC dimers with ferroelectric and antiferroelectric properties which can be incorporated into LC mixtures to enhance performance. However, existing dimers often feature high melting temperatures, enthalpies, and other physicochemical characteristics that render them unsuitable as dopants in antiferroelectric liquid crystal (AFLC) mixtures targeted to modern photonic devices. Here, we show the design and physicochemical properties of novel dimers which are characterized by low melting points, high tilt angles and spontaneous polarizations, temperature-stable helical structures, and reasonably broad temperature ranges of ferroelectric or antiferroelectric phases. These features have facilitated the effective use of one dimer as a dopant in AFLCs. This eliminates the primary drawback of the electro-optical effect based on the surface-stabilised geometry of AFLCs by strongly promoting the anticlinic state in this effect. Importantly, for the first time, the above can be achieved without affecting any other physicochemical or optical properties of AFLCs. Thus, the obtained results represent a pivotal link between the longstanding concept of developing AFLCs that meet the stringent requirements for electro-optical effects based on surface-stabilised geometry and the realization of novel photonic devices demonstrating all the benefits of this effect.

A Validated Chiral Chromatography Method for Enantiomeric Separation of Pomalidomide in Human Plasma.

In the present work, new chiral stationary phase high-performance liquid chromatography (CSP-HPLC) method was established and validated for the quantification of pomalidomide (PMD) enantiomers in human plasma. The chromatographic enantiomeric separation was achieved on a Daicel-CSP, Chiralpack IA 4.6 × 250mm, 5μm; because of its advantages of high degree of retention, high resolution capacity, better reproducibility, ability to produce lower back pressure and low degree of tailing. The mobile phase was maintained as methanol: glacial acetic acid (499.50ml:50μL). Ultraviolet wavelength for detection was 220nm. PMD enantiomer-I and enantiomer-II were separated at 8.83 and 15.34min, respectively. Limit of detection and limit of quantification for each enantiomer and the calibration curve of standard PMD was linear in range between 10-5,000ngmL-1. The method was validated according to The International Council for Harmonisation of Technical Requirements of Pharmaceuticals for Human Use (ICH(Q2R1)) specific guidelines. We found no interference peak with PMD chromatogram obtained. This is a simple, reliable and specific method for detection and quantification of enantiomer of PMD in human plasma sample.

Synthesis and properties of chiral liquid crystal copolymers with tunable circularly polarized luminescence

Chiral liquid crystals have received widespread attention due to their unique advantages in improving circularly polarized luminescence (CPL) properties. However, how to achieve the emission and modulation of CPL for chiral liquid crystals within intrinsic polymer-based materials through a simple strategy remains a challenge. This article proposes a simple and feasible method to synthesize CPL chiral liquid crystals and manipulate their properties by copolymerizing chiral liquid crystal monomer with luminescent monomer. A series of intrinsic chiral luminescent liquid crystal copolymers C*(x)-Py(y) with tunable CPL performance were synthesized by copolymerizing chiral liquid crystal monomer MA6C* with pyrene-based luminescent monomer MC6Py in varying ratios. The effective control of the chiral liquid crystal phase structure and CPL performance of the copolymers C*(x)-Py(y) can be achieved by altering the composition of copolymers. In the copolymers, the CPL signal is generated due to the helix induction of pyrene chromophores by the chiral liquid crystals, and the CPL signal can be inverted and amplified by the unique selective reflection properties of chiral liquid crystals. For copolymer C*(0.75)-Py(0.25), the luminescence dissymmetry factor value and solid-state fluorescence quantum yield can reach −0.052 and 43.12%, respectively.

Relay PHOS: Ligands with Fluxional Chirality in Asymmetric Palladium-Catalyzed Allylic Alkylation.

A modular route toward the synthesis of P,N ligands containing a fluxional group along the pyrazoline ring core is described. The racemic ligands were accessed in three steps from commercially available fluoroacetophenone in overall yields ranging from 18 to 76%. The enantiopure ligands were obtained using semi-preparative chiral high-performance liquid chromatography and chiral enantioselective phase-transfer catalysis. The effectiveness of the new ligands was assessed in palladium-catalyzed allylic alkylation with diphenylpropenyl acetate and dimethylpropenyl acetate. Under optimized conditions, diphenylpropenyl acetate underwent alkylation with dimethyl malonate in 98% yield and 94% ee. In general, the enantioselectivity for the product correlates with the size of the ligand fluxional group; the larger the fluxional group, the higher the selectivity.