Search Results (189)

Cholesteric liquid crystals (CLCs) possess the unique ability to selectively reflect incident circularly polarized light, exhibiting tremendous potential in diverse optical applications. In this study, a trilayer composite architecture of polymer-stabilized cholesteric liquid crystals (PSCLCs) was successfully fabricated. Introducing poly(vinyl alcohol) (PVA) as intervening barrier layers enabled the formation of independent and mutually non-interfering broadband reflection bands within each respective layer. Initially, a single-layer system was evaluated to identify the effects of component concentrations and polymerization conditions on the reflection bandwidth. Under optimal conditions, a maximum reflection bandwidth of 890 nm was achieved. Building upon these parameters, the effective concatenation of two independent reflection bands was accomplished by precisely regulating the concentration of the chiral dopant R5011 in the adjacent layers. Subsequently, the trilayer PSCLC film was constructed, ultimately broadening the total reflection bandwidth to 1650 nm. Characterization via polarized optical microscopy (POM) confirmed that the liquid crystal molecules consistently maintained a well-defined planar texture throughout the fabrication process of the multilayer films. Additionally, the film shows good infrared shielding performance. Its ability to regulate ambient light makes it highly promising as an optical filter and thermal management component in LC smart windows and emerging displays. Full article

Voltage-sensitive ion channels are glycoprotein macromolecules that carry ion currents across membranes of nerve and muscle fibers. The hypothesis presented helps explain the changes that convert an insulating ion channel into an ion conductor, stating that it undergoes a structural transformation on threshold reduction in the voltage across the membrane. Experimental data show that the excitable membrane is a ferroelectric liquid crystal. The Channel Activation by Electrostatic Repulsion hypothesis proposes the following: electrical attractions between boundary surface charges compress the polar channel into a compact smectic phase with induced dipoles. Critical depolarization eliminates surface charges and dipoles, decreasing the dielectric permittivity of the ion channel. This increases the repulsive electrostatic forces between positively charged residues in the four S4 segments. These forces form a selectivity filter dome and cause a proteinquake to a chiral nematic phase. The selectivity filter allows ions to enter as it strips their hydration waters. The permeant ions occupy hydrogen bonds of ion-conducting helices, displacing protons. Disordered regions between adjacent helices form liquid line defects. In the thermal chaos of physiological temperature, a line defect occasionally connects the inner and outer surfaces, forming a transient ion pathway that carries unpredictable surges of permeant ion currents, as observed in experiments. Tests for this hypothesis are proposed. Full article

Liquid crystal physical gels (LCPGs) combine the anisotropic properties of liquid crystals with the structural stability of soft solids. In this work, MBBA-based LCPGs were prepared using chiral oxalamide gelators 1,6-bis((O-leucylmethanol)-N-yloxalamido)hexane (6-O-Me) and 1,9-bis((O-leucylmethanol)-N-yloxalamido)nonane (9-O-Me) and thoroughly characterized for their thermal, rheological, and electrorheological behaviours. Techniques included differential scanning calorimetry, oscillatory rheology, electrorheological testing, and advanced microscopy analysis. A custom microfluidic device was developed for in situ application of an electric field and optical assessment of its influence on microstructure formation. Both gels exhibited distinct gel-like behavior, with storage moduli consistently exceeding loss moduli and sustained network stability under both short- and long-term deformations. The gelators had minimal effect on the isotropic–nematic transition of MBBA but efficiently delayed crystallization, extending the stability window by −8 °C for 9-O-Me and −14 °C for 6-O-Me. When subjected to electric fields, the gel network weakened in the nematic phase, and the fiber assembly during cooling was altered, resulting in the formation of thicker, anisotropic fibers, consistent with microscopic observations. These results illustrate how the properties of LCPGs can be tuned through molecular design and external stimuli, expanding their potential for stimuli-responsive soft matter applications. Full article

Four new porous homochiral metal–organic frameworks (MOFs), [M₂(camph)₂(bpa)]∙Solv (M = Co(II), Ni(II), Cu(II) and Zn(II)), based on (+)-camphoric acid (H₂camph) and 1,2-bis(4-pyridyl)ethane (bpa) were synthesized and characterized. The crystal structures of [Ni₂(camph)₂(bpa)] and [Zn₂(camph)₂(bpa)] were established by single-crystal X-ray diffraction analysis. Powder X-ray data prove the phase purity and isostructural nature of all four compounds. The thermal stability of [M₂(camph)₂(bpa)] was found to depend on the electronic configuration, as well as on the redox properties of the metal cation, and varied from 225 °C (M = Zn²⁺) to 375 °C (M = Ni²⁺). The reversible, solvent-induced sponge-like dynamics of the coordination frameworks was thoroughly investigated. Changes in the positions of reflexes, related to the length of the flexible bpa linker, were observed by powder XRD, pointing to transitions between an open-framework phase and a squeezed, non-porous phase in a crystal-to-crystal manner, while the integrity and connectivity of the coordination network were maintained. Size-selective adsorption from a benzene–cyclohexane 1:1 mixture on [Zn₂(camph)₂(bpa)] was studied by ¹H NMR analysis. The benzene-favorable composition of guest molecules (C₆H₆:C₆H₁₂ = 5:1) occluded within the host crystalline sponge revealed a preferable adsorption affinity towards smaller benzene compared with larger cyclohexane. High framework stability in various solvents, as well as successful molecular separation in the liquid state, validates the potential utilization of chiral porous metal(II) camphorate MOFs in important stereoselective applications. Full article

The polymer dispersed liquid crystals (PDLCs) with conical boundary conditions are considered. PDLC films with different values of the relative chirality parameter $N_0$ of chiral nematic droplets ranging from 0 to $1.32$ are studied experimentally and theoretically. In flattened spheroid-shaped chiral nematic droplets, a twisted axial-bipolar structure is formed whose twist angle increases with rising $N_0$ value. Two stable states of the structure are revealed: one with the bipolar axis oriented perpendicular to the short axis of the spheroid and another with the bipolar axis oriented parallel to it. Applying a small voltage causes the bipolar axes of the chiral nematic droplets to reorient parallel to the electric field. The structure is unwound in strong electric fields, and the droplet order parameter reaches a high value of nearly $0.95$. These features of the voltage-induced reorientation of the axial-bipolar structure explain the experimentally observed characteristic electro-optical properties of PDLC cells: high transmittance $T^{\max }\cong 0.90$ in the on-state and low control voltages of less than 35 V. The minimum transmittance of the PDLC cells decreases as the value of $N_0$ increases; for samples with $N_0\ge 0.60$, the contrast ratio exceeds 145. Full article

The functional integration of chiral liquid crystals and π-conjugated compounds has great potential for creating novel exotic materials. A series of chiral donor–acceptor (D–A)-type fluorenone derivatives was synthesized to investigate the influence of molecular structure upon their liquid-crystalline phase-transition behavior, ferroelectricity, photophysical properties, and photoconductive properties. Polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) analyses revealed that several D–A-type fluorenone derivatives exhibited liquid crystal (LC) phases. These chiral LC fluorenone derivatives exhibited polarization hysteresis in the chiral smectic C (SmC*) phase. Among the four fluorenone-based ferroelectric liquid crystals (FLCs), (R,R)-2a exhibited the largest spontaneous polarization (over 3.0 × 10² nC cm⁻²). The formation of intramolecular charge-transfer (ICT) states in each compound was evidenced by the UV–vis absorption spectroscopy. Ambipolar carrier transport in the SmC* phases of the fluorenone-based FLCs was elucidated by the time-of-flight (TOF) method. The mobilities of holes and electrons in the SmC* phases were on the order of 10⁻⁵ cm² V⁻¹ s⁻¹, which is on par with the carrier mobilities of low-ordered smectic phases in conventional LC semiconductors. Full article

This study investigates the temperature-driven transmission switching behavior of our proposed smart glass, which utilizes a biphasic liquid crystal system under continuous application of a distinctive homeotropic (H) state voltage (V_H). By ascertaining V_H at temperatures near the phase transition point, the minimum voltage required to sustain the H state in the smectic A* (SmA*) phase is identified. Interestingly, this minimum V_H is unable to induce the H state in the chiral nematic (N*) phase, thereby maintaining a low-transmission scattering state; i.e., the focal conic (FC) state. This empowers passive, bidirectional optical switching between the transparent H state (in the SmA* phase) and the scattering FC state (in the N* phase) in an unaligned liquid crystal cell. This work employs two dissimilar chiral dopants, R811/S811 and CB7CB/R5011, both capable of inducing the SmA* phase. Neither resulting cell system underwent surface orientation treatment, and a black dye was incorporated to enhance the contrast ratio. The results indicate that the more efficacious CB7CB/R5011 system achieves a contrast ratio of 17 between the transparent and scattering states, with a corresponding haze level of 78%. To further reduce energy consumption, the experimental framework was transitioned from a continuous-voltage to a variable-voltage mode, giving rise to an increased haze level of 88%. The proposed switching scheme holds promise for diverse applications, notably in smart windows and light shutters. Full article

The need for new, more effective drugs to treat cancer, infectious diseases, various parasitic infestations, and metabolic disorders requires innovative approaches to the design of promising molecules. One of these areas is the creation of hybrid structures. Lupane triterpenoids are of significant interest for such research due to their high abundance in natural sources and their renewable nature, their molecular architecture, presence of several easily modifiable functional groups, enantiomeric purity, broad spectrum of biological activity, and low toxicity. Active research into the biological properties of new pentacyclic triterpenoid derivatives, not only of the lupane series but also of the oleonane and ursane series, is evidenced by the large number of reviews and experimental studies devoted to this topic. Our interest in the modification of lupanoids stems not only from the search for biologically active compounds but also from the development of functional materials. However, the materials science aspects of lupanoid applications are virtually unknown in literature. We have tried to fill this gap and examined the possibility of using betulin derivatives to create advanced materials. The high lipophilicity and nanoscale molecular structure of these compounds make them highly promising as chiral dopants in liquid crystal compositions and organogel components. Full article

The present study focuses on the effect of doping KH560-modified cellulose nanocrystals (CNCs) on the electro-optical characteristics of polymer-dispersed liquid crystals (PDLCs). PDLC films were fabricated through the polymerization-initiated phase separation (PIPS) process and doped with CNC nanoparticles at various concentrations. At low concentrations, the CNCs at the interface, by virtue of their unique chiral characteristics, induce an orderly arrangement of liquid crystal molecules. Meanwhile, the interaction between the film’s fiber structure and the liquid crystal droplets brings about an augmentation in the arrangement efficiency. The excellent dispersion of CNCs diminishes the random alignment of liquid crystal molecules and mitigates light scattering. Additionally, it aids in the deflection of the liquid crystal director, facilitating the lubrication of the liquid crystals’ movement. It is remarkable that within the range of relatively lower CNCs doping concentrations, specifically from 0.005 wt% to 0.05 wt%, the PDLC films exhibit lower threshold and saturation voltages, faster response, enhanced viewing angle performance and higher contrast. Full article

A thermochromic cholesteric liquid crystal (CLC) mixture was prepared using epoxies. The structural color of the CLCN film was tuned by changing the concentration of a chiral dopant and the polymerization temperature. It was found the yellow CLCN film can be used as a sensor for the discrimination of methanol and ethanol which was proposed to be driven by the difference between the solubility parameters. Moreover, a colorful pattern was prepared based on the thermochromic property of the CLC mixture, which could be applied for decoration and as a sensor for chloroform. Full article

Circularly polarized luminescence (CPL) materials have shown great application potential in the fields of three-dimensional displays, bioimaging, and information encryption and decryption. The chirality enhancement of CPL by a physical chiral environment, involving the delivery of structural asymmetry from helical architectures to luminescent molecules through electromagnetic field resonance, represents an innovative approach for constructing high-performance CPL materials. Liquid crystal polymers (LCPs), possessing helical superstructures, show great potential in constructing CPL systems. By modulating the chirality transfer from the helical structural environment of LCPs to luminescent sources via distinct strategies, the CPL properties of LCP-based composites are readily generated and tailored. This review summarizes the newest construction strategies of LCP-based CPL materials and provides a perspective on their emerging applications and future opportunities. This review can deepen our understanding of the fundamentals of chirality transfer and shed light on the development of functional chiral luminescent materials. Full article

Topological orientation structures in chiral nematic liquid crystals, such as torons, exhibit promising optical properties and are of increasing interest for applications in photonic devices. However, despite this attention, their polarization and phase dynamics during formation remain insufficiently explored. In this work, we investigate the dynamic optical response of a toron generated by focused femtosecond infrared laser pulses. A custom-designed polarization holographic microscope is employed to simultaneously record four polarization-resolved interferograms in a single exposure. This enables the real-time reconstruction of the Jones matrix, providing a complete description of the local polarization transformation introduced by the formation of the topological structure. The study demonstrates that torons can facilitate spin–orbit coupling of light in a manner analogous to q-plates, highlighting their potential for advanced vector beam shaping and topological photonics applications. Full article

This study developed cholesteric liquid crystal broadband reflective films using zinc oxide nanoparticles (ZnO NPs) and homotriazine UV-absorbing dye (UV-1577) to enhance infrared shielding. Unlike benzotriazole-based UV absorber UV-327, which suffers from volatility and contamination, UV-1577 exhibits superior compatibility with liquid crystals, higher UV absorption efficiency, and enhanced processing stability due to its larger molecular structure. By synergizing UV-1577 with ZnO NPs, we achieved a gradient UV intensity distribution across the film thickness, inducing a pitch gradient that broadened the reflection bandwidth to 915 nm and surpassing the performance of previous systems using UV-327/ZnO NPs (<900 nm). We conducted a detailed examination of the factors influencing the reflective bandwidth. These included the UV-1577/ZnO NP ratio, the concentrations of the polymerizable monomer (RM257) and chiral dopant (R5011), along with polymerization temperature, UV irradiation intensity, and irradiation time. The resultant films demonstrated efficient ultraviolet shielding via the UV-1577/ZnO NPs collaboration and infrared shielding through the induced pitch gradient. This work presents a scalable strategy for energy-saving smart windows. Full article

Broadband near-infrared (NIR) reflective films are widely used in architecture and the automotive and aerospace industries for energy saving and thermal regulation. For large-area and flexible applications, it is essential to develop cost-effective, solution-processable, and long-term-stable NIR-reflective films. Here, we present a polymer-stabilized chiral liquid crystal (CLC) film that achieves broadband NIR reflection by stacking opposite-handed CLC layers with pitch gradients. We experimentally established optimal formulations of materials for both right-handed and left-handed CLCs. The resulting film exhibits high-degree broadband reflection (~95%) in the 1000–1800 nm wavelength range, while maintaining visible transmittance (~80%) in the 450–850 nm range. The concept proposed here will be widely applicable for scalable and practical NIR-filtering applications in smart glasses, sensors, and optoelectronic devices. Full article

The micro-phase segregation of two incompatible components on a nanometer scale results in a unique solvent-induced extended anisotropic arrangement. With the addition of a chiral dopant, lyotropic liquid crystals can be induced to adopt a helical structure, forming lyotropic cholesteric liquid crystals capable of reflecting incident light. In this study, to prevent fluid leakage in lyotropic materials, we encapsulated a series of hydrogel-stabilized lyotropic liquid crystals, presenting tunable structural colors visible in all directions, mimicking the color-changing characteristics of living organisms. Hydrogel scaffolds with controllable swelling behaviors were engineered by incorporating crosslinking monomers. To ensure stable integration of lyotropic liquid crystals, high-boiling-point ethylene glycol was employed as a fluid during the fabrication process. This study extensively explores the relationship between tensile force, temperature, and pressure and the color changes in lyotropic liquid crystals (LC). The results indicate that lyotropic LC membranes, stabilized by ethylene glycol and PDMS encapsulation, exhibit long-term stability, rendering them suitable for applications in temperature and pressure sensing. This approach ensures the continuous presence and stability of lyotropic liquid crystals within the hydrogel matrix. Full article