Mixed Liquid Crystals Research Articles

Dielectric anisotropy in liquid crystal mixtures with nematic and smectic phases

Abstract The modulation of dielectric anisotropy (△ε) is pivotal for elucidating molecular interactions and directing the alignment of liquid crystals. In this study, we combine liquid crystals with opposing dielectric anisotropies to explore the impact of varying concentrations on their properties. We report the sign-reversal of △ε in both the nematic and smectic A phases of these mixed liquid crystals, alongside a dual-frequency behaviour across a broad temperature spectrum. Our research further quantifies the influence of mixture ratios under various temperatures and electric field frequencies. This exploration may pave the way for the discovery of new physical phenomena.

Preliminary study of the superlubricity behavior of ZrO2/PI lubricating with liquid crystal

This article has investigated the friction behavior of a tribological system composed of a liquid crystal and polyimide. In this tribological system, ZrO2 and PMDA-ODA polyimide film used as a friction pair, and the liquid crystals used as lubricants including the single liquid crystal 5CB and the mixed liquid crystals LCs1 (5CB-5CEPO2), LCs2 (5CB-3CEPC3), LCs3 (5CB-2CEPPN), and conducted friction coefficient comparison experiments with n-hexadecane. It was found that the average friction coefficient of the LCs3 (90% 5CB + 10% 2CEPPN) is the smallest at the load of 5 N and the velocity of 200 rpm, which is 0.00113. Load and velocity selection experiments were investigated of LCs3, as well as polyimide film’s surface analysis including scanning electron microscope, white-light interference, polarization microscope, and surface-enhanced Raman scattering spectra. The results of the surface analysis indicated that some groups in the main chain and branch chain of the polyimide molecules are oriented parallel to the polyimide surface after rubbing.

SYNTHESIS, PROPERTIES, AND APPLICATIONS OF SUPRAMOLECULAR LIQUID CRYSTAL MATERIALS AND ACRYLAMIDE PORPHYRIN POLYMERS

A review of the work in the field of design, study of properties, and application of liquid crystal materials and acrylamide porphyrin polymers, performed at the Department of Chemistry and Technology of High-molecular Compounds, in the laboratory of Supramolecular and liquid crystal systems and in the laboratory of Polymer materials of the Research Institute of Macroheterocyclic compounds of the Ivanovo State University of Chemical Technology over the past 10 years, is presented. Synthetic methods were developed, mesogenic compounds and mixed liquid crystal compositions based on classical and supramolecular mesogens doped with additives containing polar, amphiprotic and chiral groups were obtained and studied. The mechanisms of chiral transport in the mesophase were studied. The results on the use of liquid crystals as light and heat stabilizers of polymeric materials are presented. Stationary phases for gas-liquid chromatography based on supramolecular mesogens, macroheterocyclic compounds with high structural selectivity with respect to various isomers were developed. Methods have been developed for the synthesis of water-soluble porphyrin polymers and porphyrin-containing hydrogels based on acrylamide and synthetic porphyrin monomers, realizable both under thermal heating and under microwave radiation. It is shown that a change in the ratio and nature of the components, as well as the polymerization conditions in the synthesis of porphyrin polymers provides targeted control of the properties of the resulting compounds. The molecular-mass and spectral characteristics of the obtained polymers, their surface morphology and sorption properties of porphyrin-containing acrylamide hydrogels are investigated. For citation: Burmistrov V.A., Aleksandriiskii V.V., Novikov I.V., Pechnikova N.L., Shilov I.V., Lyubimtsev A.V., Ageeva T.A., Koifman O.I. Synthesis, properties, and applications of supramolecular liquid crystal materials and acrylamide porphyrin polymers. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 7. P. 31-51. DOI: 10.6060/ivkkt.20236607. 6832j.

Optical and Thermal studies on CNT doped Liquid Crystal Mixtures

In the present study, effect of CNT on optical and thermal properties of mixed thermotropic liquid crystal mixture was studied by various techniques to understand their physical behavior. Some new mesophases have investigated by optical methods viz. Polarizing Optical Microscopy (POM) and Fabry–Perot Scattering Studies (FPSS). It has been observed that these new phase transition occur along with the known phase transition temperatures. These new phase transitions corresponding to new mesophases were also confirmed by thermal study using Differential Thermal Analysis (DTA). The CNT doped thermotropic liquid mixtures can be used in various display application such as LCD monitor with color variation to enhance performance. Copyright © 2018 VBRI Press.

UV Durable LCOS for Laser Processing

Liquid-Crystal-On-Silicon (LCOS) Spatial Light Modulator (SLM) is widely used as a programmable adaptive optical element in many laser processing applications with various wavelength light sources. We report UV durable liquid-crystal-on-silicon spatial light modulators for one-shot laser material processing. Newly developed LCOS consists of UV transparent materials and shows a lifetime 480 times longer than the conventional one in 9.7 W/cm2 illumination at 355 nm. We investigated the durability of polymerization inhibitor mixed liquid crystal in order to extend its lifetime.

Optical Response Associated with the Orientation and Structure of Liquid Crystals with Respect to Phosphatidylcholine Concentration

Based on the anchoring effect due to the self-assembling behavior of the phospholipid molecules at the interface between the liquid crystal and water phases on the orientation of liquid crystals, the optical response associated with the orientation and structure of liquid crystals with respect to the concentration of 1,2-didodecanoyl-sn-glycero-3-phosphocholine solution has been investigated. The optical response owing to changes in the orientation and structure of the mixed cholesteric liquid crystals with respect to the change in the concentration of phosphatidylcholine has been obtained. Moreover, the feasibility of using as-prepared mixed cholesteric liquid crystals to measure the phosphatidylcholine concentration has been verified. A methodology to measure the reflectance spectrum by using mixed cholesteric liquid crystals to sensitize the phosphatidylcholine concentration has been further realized. The sensitization effect of the mixed cholesteric liquid crystals on the measurement of phosphatidylcholine concentration was also verified.

Assembling free-standing and aligned tungstate/MXene fiber for flexible lithium and sodium-ion batteries with efficient pseudocapacitive energy storage

Free-standing aligned fiber is capable of providing sufficient electrochemical properties for fiber electrode without sacrificing flexibility, which is highly desirable for fiber batteries that are expected to be flexible and efficient energy storage. Here, we propose a free-standing and aligned tungstate/MXene fiber spun from their mixed liquid crystals colloid for fiber-shaped lithium/sodium-ion batteries. Benefiting from the 3D interconnected ion transport tunnels, fast charge transfer frameworks and minimum ion-path tortuosity provided by the aligned structures of 2D tungstate and MXene nanosheets, the fiber is endowed with both efficient pseudocapacitive energy storage and flexibility. As expected, the fiber delivers high reversible capacity, excellent rate capability and outstanding long-term cycling performance. Even under mechanical deformations, the fiber batteries can power the LED, digital timer, temperature-humidity meter, and smart wristband. This work may promote the further development of practical fiber batteries for wearable electronics.

Hierarchical mesoporous silica templated by the combination of fine emulsion and micelles

Abstract Concentrated emulsions have been widely considered as templates for the preparation of macroporous structures. Replacing concentrated emulsions by fine ones should rather lead to materials having large mesopores. However, fine emulsions were barely investigated for this purpose. On the other hand, mesostructured silica SBA-15 can be prepared from Pluronic P123 micelles according to the cooperative templating mechanism. Starting from mixture of fine emulsion and Pluronic P123 micelles, it is expected to obtain silicas with a controlled hierarchical mesoporosity. The fine emulsion has been formulated from the Kolliphor/Myristate/Water system. To get informations concerning the degree of compatibility between the two surfactants, which can affect the formation of the porous materials, the Kolliphor/P123/water system has been investigated in detail. The structural parameters of the mixed liquid crystal phases have been determined and the mixed micellar structure has been investigated by SAXS. The hierarchical porous silicas have been synthetized combining fine emulsion and Pluronic micellar solution. The materials porosity features strongly depend on the weight proportion between the fine emulsion and the P123 micelles. If this proportion is lower than 5/5, mesoporous silicas present a dual mesoporosity. By contrast, by increasing this proportion the mesopore size distribution only shows large mesopores.

Dynamic response evaluation of liquid crystal with negative dielectric anisotropy

ABSTRACT Rotational viscosity coefficient is an important material parameter affecting the dynamic response of liquid crystals. We evaluated the dynamic response of two series of mixed liquid crystals SCL17V33L00 and SCL17V28L00 with negative dielectric anisotropy on the basis of the accurate measurement of rotational viscosity. At the temperature of 25°C, 30°C and 35°C, the parallel and vertical dielectric constants of them were calculated from the dual-cell capacitance model and liquid crystal cell capacitance model. Then, the bend and splay elastic constants of them were determined by analysing the Fréedericksz transition threshold voltage in the vertically aligned nematic cell and comparing the liquid crystal layer capacitance–voltage curve through the finite-differential iteration method with experimental curve. At last, the rotational viscosity coefficients γ 1 of them were obtained by performing dynamic response simulation using Visual Fortran software. As the temperature increases, the rotational viscosity coefficient of them decreases. Although the rotational viscosity coefficient of the second mixed liquid crystal was relatively large under the same temperature, the viscoelastic ratio coefficient was small, and the figure-of-merit was large, thereby resulting in a relatively fast dynamic response.

Nanoscale Effects in One-Dimensional Columnar Supramolecular Ferroelectrics.

Organic ferroelectrics have been actively developed with the goal of fabricating environmentally friendly and low-cost memory devices. The remanent polarization of hydrogen-bonded organic ferroelectrics approaches that of the inorganic ones. Nanoscale fabrication of organic ferroelectrics is an essential aspect of high-density memory devices. A pyrene derivative with four tetradecylamide (-CONHC14 H29 ) chains (1) formed an amide-type N-H⋅⋅⋅O hydrogen-bonded one-dimensional (1D) column, which demonstrated ferroelectricity in the discotic hexagonal columnar (Colh ) liquid crystalline phase through the inversion of the orientation of the hydrogen-bonded chains. On the contrary, similar chiral pyrene derivatives bearing 3,7-dimethyl-1-octhylamide chains (S-2 and R-2) did not indicate the Colh phase and ferroelectricity. Homogeneous mixed liquid crystals (1)1-x (S-2)x (i.e., between the ferroelectric 1 and the non-ferroelectric S-2) enable the control of the nanoscale aggregation state of the organic ferroelectrics, resulting in a nanoscale effect of the 1D supramolecular ferroelectrics. Ferroelectric mixed liquid crystals (1)1-x (S-2)x were observed at x≦0.03, where one S-2 molecule was inserted after every thirty-three 1 molecule in the mixed liquid crystal (1)33 (S-2). An average (1)34 length of approximately 12 nm was required to maintain the 1D ferroelectricity, which was similar to the nanoscale limit of inorganic ferroelectrics, such as hafnium oxide thin film (≈15 nm).

Investigation of thermal and optical properties of some quartet mixed hydrogen-bonded liquid crystals

In this study, the thermal and optical properties of quartet mixtures formed at different weight ratios (1:1:1:1 and 1.5:1:1:1) from liquid crystals 4-octyloxy-4[Formula: see text]-cyanobiphenyl (8OCB), 4-hexylbenzoic acid, 4-(octyloxy)benzoic acid and 4-(decyloxy)benzoic acid were investigated by differential scanning calorimeter (DSC) and polarized optic microscopy (POM). The phase transition temperatures of the novel quartet mixtures measured in the DSC experiments are in line with the POM experiments. The experimental results clearly show that the novel liquid crystal mixtures have displayed pure liquid crystalline properties. According to the phase diagram drawn from DSC results, the nematic range of the novel mixture at the eutectic point is larger than the nematic ranges of the components. The mesomorphic structures of produced homolog complex mixtures are found to be smectic and nematic phases. But the smectic phase cannot be observed in the novel complex 1.5:1:1:1 mixture during continuous cooling. The nematic range of the novel complex 1.5:1:1:1 mixture is bigger than the nematic range of the novel complex 1:1:1:1 mixture with increasing 8OCB. Also, the nematic-to-isotropic phase transition temperature decreases with increasing the weight ratio of 8OCB in the complex quartet mixture. Another interesting result is that the produced mixtures are to be like a medical cream at room temperatures. Furthermore, order parameter and thermal stability factor of the transitions are also calculated.

Effect of magnetic nanoparticles on the nematic-smectic-A phase transition

Recent experiments on mixed liquid crystals have highlighted the hugely significant role of ferromagnetic nanoparticle impurities in defining the nematic-smectic-A phase transition point. Structured around a Flory-Huggins free energy of isotropic mixing and Landau-de Gennes free energy, this article presents a phenomenological mean-field model that quantifies the role of such impurities in analyzing thermodynamic phases, in a mixture of thermotropic smectic liquid crystal and ferromagnetic nanoparticles. First we discuss the impact of ferromagnetic nanoparticles on the isotropic-ferronematic and ferronematic-ferrosmectic phase transitions and their transition temperatures. This is followed by plotting and discussing various topologies in the phase diagrams. Our model results indicate that there exists a critical concentration of nanoparticle impurities for which the second order N-SmA transition becomes first order at a tricritical point. Calculations based on this model show remarkable agreement with experiment.

The decomposition process and kinetic analysis of benzene-based liquid crystal in hydrothermal system

Liquid crystal, while being a core component in liquid crystal displays, also has potential harmful effects on ecosystems and human health, especially when it is not treated properly. In this study, a hydrothermal process is proposed to dispose liquid crystal of 1-ethyl-4-[(4-methoxyphenyl)ethynyl]benzene (EMOPE) and mixed liquid crystal of EMOPE and 4-octoxy-4′-cyanobiphenyl (OCBPh). The effect of reaction time, reaction temperature, oxidant addition and solid-to-liquid ratio on decomposition ratio is evaluated. Products from hydrothermal decomposition of EMOPE are characterized, and two possible hydrothermal decomposition pathways are proposed. To get complete decomposition of 4mg of EMOPE, the conditions required are: 0.3mL of H2O2 addition, 3.5mL of water supply, 275°C and 5min. The decomposition kinetic analysis of EMOPE indicates that its decomposition process fits the apparent first-order reaction model. For the mixture’s decomposition, given conditions of 275°C, reaction time of 6min, 3.5mL of water supply, and 1.5 time of oxidant addition, the decomposition ratio of OCBPh reaches to 99.75%, and EMOPE can be completely decomposed.

Bazı Üçlü Karıştırılmış Hidrojen Bağlı Sıvı Kristallerin Termal özelliklerine 4-oktiloksi-4'-siyanobifenil (8OCB) mezojeninin etkisi

Bazı Üçlü Karıştırılmış Hidrojen Bağlı Sıvı Kristallerin Termal özelliklerine 4-oktiloksi-4'-siyanobifenil (8OCB) mezojeninin etkisi

Mesophase Transformation of Mixed Liquid Crystals Formed by Supramolecular Self‐Organization of 4‐Substituted Benzoic Acids

AbstractA mixed liquid crystalline system consisting of 4‐(octadeca‐1,3‐diynyl)benzoic acid (14PhDA) and 4‐tetradecanoxybenzoic acid (14OBA) exhibits different mesophases depending on their composition and the temperature. A mechanism is investigated for the formation of mixed liquid crystalline phases and the transformation of smectic to discotic lamellar mesophases. The three kinds of mesophases, the discotic columnar phase of 14PhDA, the smectic C phase of 14OBA, and the discotic lamellar phase of a mixture of 14PhDA and 14OBA, are simultaneously observed in a temperature range from 110 to 140 oC during the process of formation of the mixed liquid crystals by the molecular diffusion of 14PhDA and 14OBA. After rapid cooling the sample to room temperature, microscopic IR spectra are measured to estimate the composition ratio of 14PhDA and 14OBA at local positions in each mesophase. The composition ratio discontinuously changes at the boundary between the 14OBA and 14PhDA/14OBA phases due to a significant difference in the mesophase structures, i. e., the calamitic and the discotic phases, while the 14PhDA content continuously increases at another boundary between the 14PhDA/14OBA and 14PhDA mesophases. It is concluded that the diffusion of 14OBA dimer from the smectic phase to the discotic lamella phase is fast in contrast to the slow diffusion of disc‐like mesogens included in the discotic mesophases.

Investigation of thermo-electro-optic properties of some mixed nematic liquid crystals

ABSTRACTThe 6CB/8CB/8OCB liquid crystal mixture has been studied by Differential Scanning Calorimetry (DSC), polarised optic microscopy (POM), Semiconductor Characterization System, and Ultra-violet spectrophotometry (UV). DSC and POM results indicate that the 6CB/8CB/8OCB mixture exhibits liquid crystalline properties. The capacitance-voltage and conductance-voltage measurements were performed in the frequency range of 200-500 kHz and in the temperature range of 30oC–50oC. The 6CB/8CB/8OCB mixture showed an extremely large positive dielectric anisotropy. The molar absorptivity ϵ for the 6CB/8CB/8OCB mixture was calculated and found to be higher than the absorptivity values of the binary mixtures due to the alkyl chain length with H-aggregation.

Thermal and Optical Properties of Some Hydrogen-Bonded Liquid Crystal Mixtures

Phase transition properties of the mixtures of hydrogen-bonded nematic liquid crystals (HBLC) 4-hexylbenzoic acid (6BA), 4-(octyloxy)benzoic acid (8OBA), and 4-(decyloxy)benzoic acid (10OBA) have been investigated by means of differential scanning calorimetry (DSC) and polarize optic microscope (POM). The DSC and POM results clearly indicate the existence of smectic and nematic phase transitions in binary mixtures. The phase transition temperature values of 6BA/10OBA mixtures have clearly increased with increasing heating rate. The activation energies were calculated for the phase transitions of 6BA/10OBA liquid crystal (LC) mixture. The optical transmittance of these mixed hydrogen-bonded nematic liquid crystals was investigated in terms of temperature variations through electrooptic methods. The electrooptic experiments indicate that, while low in the nematic phase, the optical transmittance is very high at the nematic-isotropic phase transition. The transmitted light intensity values of 6BA/8OBA mixture are somewhat higher than those of other binary mixtures, 6BA/10OBA and 8OBA/10OBA, a result associated with the different alkyloxy chain lengths.

Determining mainstream reference temperature using the non-dimensional temperature analysis in the transient liquid crystal technique

Transient thermochromic liquid crystal technique (TLC) has been widely used for measuring surface temperature distribution and local heat transfer coefficient (h). For flow inside ducts, the mass-flow-averaged temperature (Tm) and the adiabatic wall temperature (Taw) are often used as mainstream reference temperature. They are difficult to measure and a systematic error is often introduced into the results. In the present study, a novel method is developed to resolve the mainstream reference temperature from the measured temperatures at several locations using non-dimensional temperature analysis. TLC experiments of a square channel with vertical ribs, 45° ribs or V-shaped ribs are carried on, with relative CFD simulations. It is showed in the results that using the non-dimensional temperature analysis method, Nusselt number based on Tm can be adjusted by 4–15%, especially when there is large spanwise temperature variations. The systematic error of transient experiments is reduced. Taw and h can be solved in the experiments using mixed liquid crystals whether mainstream temperature history is an ideal step or not.

四环二氟甲醚桥键液晶化合物性能研究

Liquid crystalline compounds with difluoromethyleneoxy linkage group are widely used in liquid crystal mixtures.However,their phase behavior and physical properties have not been reported systematically.The mesomorphic properties of two series of compounds 1 and 2 with cyclohexyl group were thoroughly studied by using differential scanning calorimetry(DSC)and polarizing optical microscopy(POM).The effect of all the compounds on the mixtures were systematically investigated and their physical parameters were extropolated by using addition principle.The results show that compounds 1 have higher clearing point and wider nematic phase temperature range than that of compounds 2.Due to the increase of a fluorine atom on the skeleton,compounds 2 have higher dielectric anisotropy than that of compounds 1.Compounds 1 can significantly improve low temperature miscibility and broaden the mixed liquid crystal temperature range.

P.73: WITHDRAWN: P.74: Polymer Stabilized Double Twist Cylinders of Blue Phase Liquid Crystal for Reduced Hysteresis and Operating Voltage

AbstractIn this paper, we have reported a novel method for reducing hysteresis and operating voltage by stabilizing the disclination lines as well as double twist cylinders (DTCs). We have stabilized DTCs by incorporating photo reactive chiral monomer (SRM3) into the monomer mixed host blue phase liquid crystal (BPLC). Hysteresis and operating voltage of the proposed stabilized BPLC is reduced compared to the only disclination line stabilized BPLC.