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We report on a set of experiments directed to a problem of microparticles interaction with a disclination in a nematic liquid crystal matrix. The idea of the study consists in the visualization of the disclination by filling it with particles efficiently scattering light. A θ-cell possessing a topological defect of undetermined twist which can capture micro-sized objects was exploited. The results obtained for samples of different shape can be used as for the understanding of the nature of self-assembling clusters, as for the practical goal of increasing the visibility of a disclination being a dynamic object sensitive to temperature and other external factors and able to move the trapped particles. [ABSTRACT FROM AUTHOR]

Laguerre–Gaussian (LG) beams with a spiral phase (optical vortex), which feature orbital angular momenta, and vector beams (VBs) with an axially symmetric spatial polarization distribution exhibit properties different from those of conventional Gaussian beam. In this article, we introduce LG beams and VBs. Next, we explain the generation of LG beams and VBs using liquid-crystal devices. Subsequently, we report the super-resolution observation of biological samples and our observation of a PNLC (Polymer network liquid crystal) network structure using a laser scanning microscope, which comprises a liquid crystal LG-VB generator. Finally, we discuss the conservation of spiral beams and their application to optical wireless communication. [ABSTRACT FROM AUTHOR]

The main goal is to study the structural and dielectric characteristics of advanced composite materials based on ionic metal alkanoates with various types of nanoparticles. The matrix Cd+2(C7H15COO)−2 formed as a result of the reaction of cadmium with the carboxylate groups of alkanoate (C7H15COO)−2 is used for the synthesis of nanoparticles. At room temperature, the matrix of the ionic crystalline material represents multilayer structure with each layer thickness of 1.8 nm. However, when heated in the temperature range from 100 °C to 180 °C, the matrix undergoes a phase transition into the liquid crystalline smectic A phase, preserved after cooling to room temperature. This transition opens up possibilities for the synthesis of carbon and gold nanoparticles. The temperature treatments of the matrix allow to control of the size and shape of nanoparticles during synthesis and create highly stable nanocomposites. The structural features and dielectric properties of these nanocomposites are studied using transmission electron microscopy, enabling to determine of the sizes of nanoparticles and their dispersion and impedance spectroscopy, respectively. Dielectric properties of nanocomposite materials were studied at different temperatures corresponding to two material phases. We carried out an analysis of the dielectric characteristics of the pure matrix in comparison with nanocomposite materials, containing carbon and gold nanoparticles to identify the role of the nanoparticles. Based on our experimental data, we proposed a model to explain the charge transfer process, taking into account relaxation processes and polarization of nanocomposite materials. [ABSTRACT FROM AUTHOR]

A nano-structured surface containing an Au nano-island film is used to fabricate hybrid liquid crystal (HLC) cells. HLCs are characterized by faster response times. The dynamic holographic technique is applied to make the conversion of the laser pulse shape by using HLCs. From a comparative analysis of experimental results with theoretical modeling of a dynamic process, the time constants of the dynamic grating recording and relaxation have been determined. [ABSTRACT FROM AUTHOR]

We review recent research in various types of optical quantum computing using liquid crystal devices. First, we have investigated Young's Interference experiment using self-aligned liquid crystal (LC) devices and a logical "NOT" operation is achieved. Second, numerical quantization of interfering small photons using an LC retarder is investigated. Third, a Mach–Zehnder interferometer with an optical phase control by a twisted nematic (TN) LC device was studied. Fourth, a basic experiment on 2-bit quantum calculations related to the Deutsch-Jozsa algorithm on a linear optical quantum computer using the LC device as a linear optical element was investigated. [ABSTRACT FROM AUTHOR]

A novel homologous series of cinnamoyl ester comprising of elven (C1 to C16) homologues liquid crystal (LC) samples have been synthesized and characterized using instrumental methods (spectral and thermal) of analysis and DFT approach. As results, middle ordered melting type of series with exhibition of nematic mesophase were observed. The observed mesogenic properties and transition temperature are affected by the size of alkyl chains that shows mesomorphism is susceptible to molecular structure. The prepared LCs of cinnamoyl ester derivatives were further examined for their biological activities and the obtained results indicates a good biological potential for the studied LC materials. [ABSTRACT FROM AUTHOR]

The director deformation inside a nematic cell, after a magnetic field is applied at an oblique angle α relatively to the initial homogeneous director, is studied considering a magnetic reorientation driven by hydrodynamic instabilities. This study is carried out for the splay and the bend non-Freedericksz geometries with α<π/2. Critical sample thicknesses are predicted for both the homogeneous deformed and the periodic director reorientations, giving way to a stripe pattern in the last case. The first transition, to homogeneous deformed director, is the equivalent of a second order phase transition, while the second transition, to a periodic director, is the equivalent of a first order phase transition. [ABSTRACT FROM AUTHOR]

A liquid crystal is used as an electro-optical device with the advantages of low voltage driving, low power consumption, and thin flatness by utilizing its refractive index anisotropy (birefringence). In this research, a liquid crystal tunable filter (LCTF) with control of a main peak wavelength λ0 and a full-width Δλ at half maximum is developed. The device contains two stacking liquid crystal layers with different wavelength dependences of birefringence Δn with their optical axes perpendicular to each other and controlling the light wavenumbers in a complementary manner (S-ECB). [ABSTRACT FROM AUTHOR]

Novel hydrogen bond liquid crystal (HBLC) complexes are prepared from the combination of non-mesogenic (α, ω-dicarboxylic acid) 2, 2-Dimethylsuccinic acid (DMSA) and liquid crystalline 4-n-alkyloxybenzoic acids (nOBA, n = 7 to 12). Mesogenic behavior of all complexes is analyzed by polarized optical microscope (POM) along with their thermal properties using differential scanning calorimeter (DSC). The microstructure of DMSA + 11OBA HBLC complex is observed by Field emission-scanning electron microscope (FE-SEM). The molecular geometry of DMSA + 7OBA HBLC complex is optimized. Intermolecular H-bonding of complexes is evinced using experimental and theoretical Fourier transform infrared spectroscopy (FTIR). Natural bonding orbitals (NBO) study supported the occurrence of H-bonds. [ABSTRACT FROM AUTHOR]

The effect for polymerizable layer on a vertical-type photo-alignment layer was investigated from the point of image sticking characteristics. Fabrication process of the polymerizable layer is followings; photo-alignment treatment is firstly carried out by exposing polarized ultraviolet (UV) from the oblique direction. After construction of the liquid crystal (LC) cell, the LC material including monomers is injected, and unpolarized UV is exposed for formation of the polymerizable layer. For avoiding pretilt angle shift during the exposure, fast rate constant of polymerization is necessary, and mixed monomers 4,4'-dimethacryloyl-oxy-biphenyl (4,4'-DMABiph) and 4,4'-dimethacryloyl-oxy-benzilketal (4,4'-DMABzk) are appropriate for obtaining small level of image sticking parameters. As the image sticking parameters, residual direct current voltage (VrDC) and difference in pretilt angle (Δtilt) before and after application of alternate current voltage were evaluated, and the results of VrDC and Δtilt indicated that 6% 4,4'-DMABzk in the mixed monomers 4,4'-DMABiph and 4,4'-DMABzk would be useful for obtaining the small level of image sticking. [ABSTRACT FROM AUTHOR]

In this research, we report the synthesis of conjugated polymers with magnetism. Electrochemical polymerization in liquid crystal was conducted with 1-butyl-3-methylimidazolium tetrachloroferrate (BMITF), which is a paramagnetic character having a large magnetic susceptibility, as a supporting salt. The polymer films thus obtained had magnetism because BMITF remains in the films as a dopant. Poly(2,2′-bithiophene) and poly(bis-(3,4-ethylenedioxythiophene)) were prepared in nematic or cholesteric liquid crystal with BMITF by electrochemical polymerization. Transcription of the liquid crystal structure was succeeded with a small amount of BMITF. Blush or fingerprint structures were confirmed by polarizing optical microscopy observation. The addition of the excess amount of BMITF broke the structure of the liquid crystal. Poly(2,2′-bithiophene) transcribed the cholesteric liquid crystal structure showed a negative Cotton effect, indicating with left-handed helical structure. Poly(bis-(3,4-ethylenedioxythiophene)) transcribed the cholesteric liquid crystal structure showed a positive Cotton effect, indicating the polymer forms a right-handed helical structure. The X-ray photoelectron spectroscopy measurements, confirming the existence of Fe element in the polymers thus obtained. From the electron spin resonance measurements, the polymers thus obtained showed magnetic activity. This method affords facile synthesis of conjugated polymers with magnetism. [ABSTRACT FROM AUTHOR]

An amphotropic liquid crystal polyacetylene derivative with pyrimidine–type two-ringed mesogenic core, exhibiting both thermotropic and lyotropic liquid crystallinity, was synthesized in this study. The polyacetylene derivative showed a lyotropic liquid crystal in d-limonene. The cis configuration of the main chain was confirmed via1H NMR. Heat treatment induced cis–trans isomerization of the as-prepared polymer. Gas-phase iodine doping of the polymer initiated a chemical interaction between the polyene and iodine, acting as an electron acceptor, generating charge carriers (radical cations, solitons) detected with the electron spin resonance spectroscopy. Moreover, gas phase doping of the polymer induced cis–trans isomerization. [ABSTRACT FROM AUTHOR]

The paper presents a comparative analysis of liquid crystal cholesteric-nematic mixtures for their use as sensitive elements of gas sensors. Liquid crystal mixtures based on nematic mixture E7 and cholesteric impurity CB15 were considered. In order to determine the optimal mixture, a study of the spectral characteristics of the mixtures was carried out, and the main transmission peaks were determined for different concentrations of the optically active impurity. The temperature characteristics were measured to determine the threshold values for the transition of the mixtures to the isotropic state and stable temperature areas. As a result of the conducted research, we can state that as a sensitive element of optical sensors, it is advisable to use liquid crystal mixtures with impurity concentrations of CB15 of 38% and 44%. Their main transmission peaks are in the visible region of the spectrum of 500-600 nm. The temperature characteristics are slightly better in the 38% mixture, but we can claim a slightly higher sensitivity to organic substances in the 44% mixture. Further research of mixtures can be carried out during the direct development of optical sensors. [ABSTRACT FROM AUTHOR]

In this article, we designed and synthesized two novel swallow-tailed liquid crystal monomers (M1 and M2) with different chain lengths and rigidities centered on 3,4,5-trihydroxybenzoic acid and two series of side-chain liquid crystals polymers PN1 and PN2. All liquid crystal monomers and polymers were conformed to the molecular designs by FT-IR and NMR. The liquid crystal properties were tested by DSC and POM, and the results showed that M1 and M2 were thermotropic enantiotropic nematic liquid crystals and the side-chain liquid crystal polymers PN1 and PN2 series were typical amorphous liquid crystal polymers. With the increase of monomer content, the glass transition temperatures and clearing points of PN1 and PN2 series enhanced. With the increase of the number of mesogens in the liquid crystal monomer, the rigidity was enhanced, and the liquid crystal performance of the polymer was better. [ABSTRACT FROM AUTHOR]

A new class of λ-shaped azo materials with a cinnamate linkage group has been designed, synthesized, and well-characterized. Further, the liquid crystalline property has been studied by using POM and DSC analysis. Out of six derivatives, five compounds displayed liquid crystalline properties. The liquid crystalline property is observed in an enantiotropic manner. The structure–property relationship is further studied for the understanding of the exhibition of liquid crystalline properties. The results showed that their liquid crystalline phase behavior was closely related to the number of mesogenic units, rigidity, and flexibility of the molecular systems. [ABSTRACT FROM AUTHOR]

We study the nature of the nematic to smectic-A phase transition under confinement conditions in the context of Landau-de Gennes theory. The effect of quenched disorder on the nematic to smectic-A transition temperature, order parameter, enthalpy, and thermal hysteresis are discussed followed by phase diagrams. The tricritical behavior of the nematic to smectic-A phase under confinement conditions is predicted. [ABSTRACT FROM AUTHOR]

Linear hydrogen bond liquid crystal (HBLC) series comprising of 4- hydroxy benzaldehyde (HBA) and p-n alkyloxy benzoic acids (nBAO) have been intensively investigated for their optical and thermal applications. Fourier transform infrared spectroscopy (FTIR) obtained for all the mesogenic complexes reveals the optical applicational utility of the homologues as high pass, low pass and notch filters in the mid IR range. Differential scanning calorimetry (DSC) datum identifies the thermal equilibrium possessed, thermal stability factor of the individual mesophases, nature of the enthalpy, entropy of the mesophases and specific heat temperatures along with phase transition temperatures. [ABSTRACT FROM AUTHOR]

In this work, we reported a facile method to fabricate a liquid crystal/physical gel/polymer composite film. The liquid crystal physical gel was prepared by self-assembly of sorbitol-based gel factor in commercial liquid crystal E7. The polymer network was introduced to the system to optimize the electro-optical properties of the liquid crystal physical crystal. The electro-optical performance indicated that the driving voltage significantly reduced from 85 to 45 V and the contrast ratio was increased more than tripled when there was 8 wt% content of polymer. [ABSTRACT FROM AUTHOR]

A novel phase was fabricated using a liquid crystal medium, and its feasibility as an ion-conducting material was explored. The intermediate phase comprised a strong polar compound and a low-molecular-weight nematogen, which was insoluble in the compound. Nanoscale phase segregation occurred between the host nematogen and guest polar compound upon dispersing a small amount of the polar compound into the nematogen. This nano-segregated phase was characterized through polarized optical microscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy. Furthermore, the ionic conductivity of the nano-segregated phase was qualitatively evaluated by voltage holding ratio measurements. [ABSTRACT FROM AUTHOR]

Binary mixtures of double hydrogen bond liquid crystals are investigated by chemical, optical and thermal studies. These binaries exhibiting rich phase polymorphism, in which hydrogen bond is formed between Methyl Malonic acid (MM), heptyloxy benzoic acid (7BOA), and decyloxy benzoic acid (10BOA) abbreviated as MM + 7BOA and MM + 10BOA. MM + 7BOA (X) is considered as one of the variants while MM + 10BOA (Y) is considered as other variant. Appropriate molar ratio (0.1X to 0.9X and 0.1Y to 0.9Y) variation in the precursors leads to formation of nine binary mixtures. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene) (PEDOT) film was electrochemically prepared in nematic LC solvent under centrifugal force. Polarized ultraviolet-visible (UV-Vis) absorption spectra and polarizing optical microscopy (POM) images of the polymer film indicate orientation perpendicular to centrifugal force direction. PEDOT alignment was achieved during the polymerization through alignment of the liquid crystal matrix by centrifugal force. The monomer was polymerized along the liquid crystal alignment to form oriented PEDOT. Visualization of LC director was achieved by electrochemical polymerization in the LC. [ABSTRACT FROM AUTHOR]

Molecular asymmetric imprinting polymerization in the cholesteric liquid crystal was carried out. An L-isoleucine derivative with fluorine was synthesized for a chiral inducer to induce the cholesteric liquid crystal from the nematic liquid crystal. A substance with multiple asymmetric centers can be obtained conveniently to use amino acid as chiral substance. The L-isoleucine derivative induced helical structure for 4-cyano-4'-hexylbiphenyl (6CB). Electrochemical preparation of π-conjugated polymers was carried out in the cholesteric liquid crystal. Fingerprint texture derived from the cholesteric liquid crystal was transcribed to the polymers. UV-vis and circular dichroism (CD) spectra of oxidized (doped) for and reduced (dedoped) form of the polymer were measured. Electrochemical polymerization in the helical liquid crystal produced the molecular aggregation imprinted chiral polymers, which have liquid crystal-like aggregation form, chirality with no stereogenic center via formation of polymer atropisomer, and electrochemical driven change in optical activity, as a form of electro-optically coloration active polymers. Finally, the polarons and bipolarons are in the form of chiral structure. These charge carriers in the polymers can be determined as chiral charge carrier "chiralions". [ABSTRACT FROM AUTHOR]

A series of swallow-tailed Schiff base liquid crystals with different end groups were synthesized and characterized. 4-chlorobenzoic acid, 4-methylbenzoic acid and 4-methoxybenzoic acid were connected with three hydroxyl groups of cholic acid by acyl chloride method to obtain intermediates SB-R1, SB-R2 and SB-R3. Schiff base phenol S-X1, S-X2 and S-X3 were linked with carboxyl groups of intermediate cholic acid to obtain the target compounds through esterification reaction. The structures of five kinds of swallow-tailed Schiff base liquid crystal compounds (SSB-RX1∼SSB-RX5) were characterized by IR、1H-NMR、13C-NMR and elemental analysis and liquid crystal performance was analysed by POM and DSC. The results showed that the five target products had good mesomorphic property and they all exhibited enantiotropic nematic phase which had schlieren texture and droplet texture. [ABSTRACT FROM AUTHOR]

Emulsions of isotropic liquids have spherical phase boundaries. Liquid crystals have elastic forces associated with the director distortions and preferred boundary conditions that can also play a role in defining the phase boundary shape. Here we show a liquid crystal in liquid crystal emulsion where a chemically distinct guest phase resides in the topological disclinations of the host phase. These disclinations act as effective capillaries and various meniscus and droplet phenomena are observed. This "topological capillary emulsion" shows that additional forces associated with anisotropic molecules can play a critical role in determining the shape and properties of a phase boundary. [ABSTRACT FROM AUTHOR]

The rod-shaped materials based on chalcone and cinnamate groups were designed and synthesized for the study of liquid crystalline properties. In the present study, seven homologous have been synthesized by varying alkoxy side chains, and the liquid crystalline property was preliminarily investigated by POM, DSC, and XRD study. The lower alkoxy chain displays nematic mesophase, while the higher chain displays smectic C and nematic mesogenic behavior. Also, the structure–property relationship was studied by changing terminal alkoxy chains. The analytical approaches such as FT-IR, 1H NMR, and 13C NMR spectroscopy were used to confirm the molecular structure of the compounds. [ABSTRACT FROM AUTHOR]

In this work, the thiol‐ene click reaction was used to prepare polymer-dispersed liquid crystal films by a photo-initiated polymerization reaction. Different content of DET was introduced into the polymer matrix to enhance the electro-optical performance of PDLC. Our results showed that the introducing of DET significantly improved the electro-optical properties of PDLC. The SEM results showed that larger and uniform pores were observed with increasing DET content. And it was found that an increase in UV intensity resulted in a continuous decrease in Toff and an increase in CR for weakening the anchoring effect of the polymer matrix. [ABSTRACT FROM AUTHOR]

We demonstrate controllable transmittance in an NIR-GH-LC device mediated by irradiation with pseudo-sunlight. Optical phase transition is induced in the proposed NIR-GH-LC device by the opto-thermal conversion of near-infrared dye, and the transparent and colored states are controlled with dichroic dye. Our results indicate that the optical phase transition can be observed upon irradiation with pseudo-sunlight when the concentration of near-infrared dye is 5 wt%, with the dichroic black dye also contributing to the optical phase transition via opto-thermal conversion. We find that the proposed NIR-GH-LC device can be switched between the transparent and colored states by irradiation with pseudo-sunlight. The NIR-GH-LC device is attractive for applications in self-shading smart windows that can be driven by sunlight. [ABSTRACT FROM AUTHOR]

Liquid crystals (LCs), whose refractive index can be changed by light irradiation, can be used as photoresponsive optical materials. In this study, an LC viologen was proposed as a novel photoresponsive compound that induced a change in the alignment of LC molecules (mesogens). An extended viologen with an asymmetric core, that exhibits a low-order LC phase at room temperature, was mixed with the well-known nematic LC compound (5CB) to prepare homogeneously aligned films. The change in the alignment of the mesogens was successfully induced by triggering a one-electron reduction reaction of the viologen moieties by light irradiation. [ABSTRACT FROM AUTHOR]

Four dichiral liquid crystals with one perfluoroalkyl chain and two lactate groups were synthesized. They all exhibit an enantiotropic SmA phase. An enantiotropic SmCd* phase was identified in a pair of enantiomers. Their optical activity was mainly controlled by the chirality of the lactate residue near mesogenic core. These liquid crystals could self-assemble into twisted nanoribbons or helical nanofibers. The stacking handedness of mesogenic cores and the handedness of nanoribbons/nanofibers were also dominated by the chirality of lactate group near mesogenic core. This "core determination" phenomenon was proposed to originate from the π–π stacking among mesogenic cores. [ABSTRACT FROM AUTHOR]

Novel hydrogen bond liquid crystal homologous series derived from alkyloxy benzoic acids and α-ketoglutaric acid are isolated and experimented. This homologous series referred as KGA + nBAO comprises of eight mesogens in which the alkyloxy benzoic acid varied from pentyloxy to dodecyloxy. Fourier Transform Infrared Spectroscopy analysis confirmed the formation of hydrogen bond. Optical polarizing microscopy reveals that this homologous series exhibits three phases namely nematic, smectic C and smectic G. The transition temperatures obtained by Differential Scanning Calorimetry and optical microscopy and corresponding enthalpy values are tabulated for all the homologues of the series and various thermal parameters are derived. [ABSTRACT FROM AUTHOR]

In this study, a polymerizable chiral dopant end-capped with menthyl group was synthesized. The solubility of the polymerizable chiral dopant in a mesogenic host was also studied. The film with left-handed broadband reflective capability was prepared via employing the chiral dopant and a bifunctional mesogenic compound as the polymerizable monomers. To enhance the reflection of the broadband reflective film, two films that reflected left-handed circularly polarized light and right-handed circularly polarized light, respectively, were superimposed to obtain a composite film. The reflection of the composite film for the light with the wavelength between about 800 and 1150 can exceed 60%. [ABSTRACT FROM AUTHOR]

A series of liquid crystal elastomer films (the PBC series) have been synthesized by grafting liquid crystal (LC) monomer 4-allyloxybenzoic acid cholesteryl ester (MB) and crosslinking agent [1,1'-biphenyl]-4,4'-diyl bis(undec-10-enoate) (MC) onto polymethylhydrosiloxane catalyzed by hexachloroplatinic acid at 60 °C. The PBC series are cholesteric liquid crystal elastomers (LCEs). The glass transition temperatures (Tg) of the PBC series are between 23-33 °C, and the LC range is above 200 °C. The temperatures of 5% weight loss of the PBC series are above 300 °C, which shows good thermal stability. The PBC series display good orientation. PB3C3 shows a good ability of shape recovery above Tg. [ABSTRACT FROM AUTHOR]

The photovoltaic effect in pure cadmium-alkanoate matrices and in their nanocomposites with semiconductor CdS nanoparticles (NPs) was revealed and investigated. The main mechanism of the phenomenon is the Dember effect, in which the internal field of non-equilibrium charge carriers is formed due to a significant difference in the mobility of positive and negative charges. NPs synthesized in the matrix lead to a significant increase in the concentration of the photo-generated electrons and thus to an increase in the photo-electro-driving force in the material. The magnitude and kinetics of the photocurrent for nanocomposites substantially depend on the content of only a small amount (2 − 4 mol. %) of NPs. [ABSTRACT FROM AUTHOR]

Compound synthesized N-[4-((2R)-octan-2-yloxy)benzyl]-N,N-dimethyl-hexadecane-1-aminium tosylate, which is a promising candidate for use in liquid crystal compositions. The Raman spectrum of the synthesized sample was also recorded. The equilibrium configuration of the molecule (ion) was calculated by optimization for all geometric parameters at the level of the B3LYP/cc-pVTZ theory. In addition, the equilibrium configurations of three more stable conformers of the molecule were calculated. The relative energies of the four conformers, their dipole moments were determined, and their IR and Raman spectra were calculated. Comparison of the calculated and experimental vibrational spectra of the molecule made it possible to assign the absorption bands and Raman scattering lines to the vibrations of molecular fragments. [ABSTRACT FROM AUTHOR]

We report the new results on the measurements of diffraction efficiency in liquid crystal (LC) cells with different orienting surfaces in the presence of a DC electric field. Diffraction gratings were recorded in combined cells with E7 liquid crystal. We used LC cells with thickness of ∼10 µm. Gold nanoparticles, chalcogenide and ITO nano-surfaces were used as command surfaces. Diffraction gratings were formed during irradiation of LC cells by 2-beam spatially modulated laser light (λ = 532 nm) with linear p-polarization in experiments of two-wave mixing. As a result, we found an asymmetry in the diffraction efficiency of the recorded gratings in different cells, which depends on the type of command surface and the polarity of applied voltage. The obtained results are appropriately described in the terms of surface-induced photorefractive mechanism, when a diffraction grating arises due to the formation of an unstable charge in pure liquid crystal. We believe that unstable charge depends on a surface on which different types of charge carriers are excited by light. [ABSTRACT FROM AUTHOR]

The effect of the 5CB liquid crystal cooling rate on its luminescence spectra at the low temperature (T = 4.2 K) has been found and studied for two types of nanocomposites: 5CB liquid crystal, doped by carbon nanotubes (NT) or so-called hybrid nanoparticles (NT + OMMT). Hybrid nanoparticles were prepared from organomodified layered montmorillonite minerals (OMMT) with the addition of carbon nanotubes. Experiments have been carried out at two cooling rates, 2 and 10 K/min. Structure of the luminescence spectral bands is associated with 5CB crystallization peculiarities and formation of its glass-like state under different cooling regimes of the isotropic phase. The reasons for the short-wavelength shifts of the luminescence peaks for the 5CB–(NT + OMMT) sample compared to the 5CB–NT one are discussed. [ABSTRACT FROM AUTHOR]

As a model of polymer-sustained-alignment liquid crystal display (PSA-LCD), the LC cells having the PSA layers (PSA-LC cells) formed by mixed monomers of 2,7-dimethacryloyl-oxy-phenanthrene (2,7-DMAPhen) and 4,4'-dimethacryloyl-oxy-benzophenon (4,4'-DMABenz) were fabricated, and image sticking parameters and long-term stability under LED-backlight exposure were investigated. Residual direct current voltage (VrDC) and difference in pretilt angle (Δtilt) before and after application of alternate current voltage were evaluated as the image sticking parameters. The VrDC was improved with the addition of a small amount of 4,4'-DMABenz because the concentrations of radical and/or ion in the LC layer had decreased significantly. It was shown that with the addition of 3.8 wt% of 4,4'-DMABenz in the mixed monomers, VrDC can be kept low without increasing Δtilt. Voltage holding ratio was maintained high under the LED-backlight exposure for 1,000 h, indicating that the PSA-LC cell shows high long-term stability. Hence we expect that the proposed PSA-LC cell would be useful for high luminance LCDs. [ABSTRACT FROM AUTHOR]

A new fabrication technique and mixed monomers for a polymer-sustained-alignment liquid-crystal (PSA-LC) cell were proposed in this study. The proposed process for formation of the PSA layer is exposing visible light for polymerization instead of exposing ultraviolet (UV) light. The backlight consisted of light emitting diode (LED) for the LC display (LCD) was used as the source of the visible light, and the mixed monomers were 2,7-dimethacryloyl-oxy-phenanthrene (2,7-DMAPhen) and 4,4'-dimethacryloyl-oxy-benzil (4,4'-DMABzl). Since the monomer 4,4'-DMABzl could generate radicals by a hydrogen abstraction reaction under exposure of the visible light, the PSA layer was formed under the LED-backlight exposure through an intermediary of a polarizer. The fabricated PSA-LC cell showed equal level of voltage holding ratio, residual direct current voltage, and difference in pretilt angle before and after application of an alternate current voltage to the PSA-LC cell fabricated by the UV light exposure. Therefore, we expect that future PSA-LCD would be fabricated without exposure of the UV light. [ABSTRACT FROM AUTHOR]

Liquid crystals have numerous applications in various fields ranging from drug delivery, gene therapy in biosciences to electronic display and sensors in the field of opt-electronics and material science. In recent years, the properties of liquid crystals have been tailored by truncating the terminal atom(s) or group of atoms and/or by doping different types of nanomaterials; such as nanodots, nanorods, nanotubes, nanoplatelets, etc. Controlled assembly of nanoparticles in liquid crystal media can provide an alternative method to tailor new and desired opto-electronic properties in uniquely arranged quantum dots. This self-assembly of nanoparticles produces new hybrid (composite) materials having large number of applications. Here, we review different applications of nanoparticles and liquid crystal systems and highlight different approaches for achieving the hierarchical arrangement of nanoparticles in liquid crystal media. Here, phenomena like quantum dot self-assembly, formation of hollow microstructures, memory effect, and formation of microcapsules, etc. in presence of liquid crystal media are revisited and discussed critically. Band-gap-tailoring has emerged as a major thrust area because of numerous applications in making opto-electronic devices. Band-gap of liquid crystals can be also be tailored either by doping (metal) atoms or by nucleating their nano-clusters after removing their terminal groups. This phenomenon creates a lot of attraction among scientists. Hierarchical arrangement of nano-dots in liquid crystal media has gained a lot of interest, as they can possess special functional properties; many of which are known whereas many others need to be discovered. Hierarchical arrangement of nano-clusters can be obtained either by doping atoms into liquid crystals followed by a nucleation process or by forming molecular architectures by weak coupling between quantum dots because of van der Waal forces. Functional properties such as magnetic, physiochemical, and opto-electronic properties of the hybrid systems are different from their constituent parts, and thus the hybrid systems can find a vital role in the field of nanoscience and nanotechnology. Because of the aforesaid reasons, it has gained much attention in the last few decades. [ABSTRACT FROM AUTHOR]

Poly(bithiophene) was synthesized in a nematic liquid crystal under a magnetic field. The polymers prepared by electrochemical polymerization exhibited an aligned schlieren texture parallel to the magnetic field direction. As a function of linear polarized electrochromism, the poly(bithiophene) thus obtained shows linear dichroism with color change via electrochromism. [ABSTRACT FROM AUTHOR]

A series of pyridinium-based chiral ionic liquid crystals were designed and synthesized. All of them exhibit enantiotropic smectic phases. The methylation on the pyridine ring not only decreases the melting point and clearing point, but also drives structural transitions from bilayer molecular packing structures to interdigitated monolayer ones at the smectic A and C phases. Due to entropy increase, the clearing point of the liquid crystal derived from 2-methylpyridine is higher than that derived from 3-methylpyridine, and then that derived from 4-methylpyridine. [ABSTRACT FROM AUTHOR]

A series of compounds of with high birefringence containing alkoxy–phenylacetylene–isothiocyanato structure were synthesized and characterized. The chemical structures of these compounds were confirmed by FT-IR and 1H-NMR, and transition temperatures and birefringence were measured. One of these compounds with good liquid crystal property and high birefringence was mixed with host liquid crystal to form blend liquid crystal. The effects of the concentration of the compound on phase temperature range, birefringence, resistivity, dielectric anisotropy and photoelectric properties were discussed. The results showed that blend liquid crystal (with 7 wt% compound) exhibited excellent comprehensive performance. [ABSTRACT FROM AUTHOR]

A series of azobenzene liquid crystals containing one amino acid residue were synthesized. They exhibit smectic mesophases. The compounds derived from alanine can self-assemble into twisted nanoribbons. The molecules organized in a monolayer structure within the nanoribbon. Circular dichroism characterization indicated that the neighboring liquid crystal cores packed in a chiral structure. FT-IR spectra indicated that the nanoribbons were caused by H-bonding and association of hydrocarbon chains. [ABSTRACT FROM AUTHOR]

Two series of benzoates containing 1,2,3-triazole heterocyclic were prepared. The molecules containing alkyl chains of 12 ∼ 14 carbon atoms and with benzene ring as the central core show liquid crystal behaviors. After replacing benzene ring with cyclohexane, the compounds with short or long alkyl chains or ferrocene terminal group have no mesomorphic behavior. However, the compounds with medium length alkyl chain have lower melting point and wider mesomorphic domain than those with benzene ring as the central core containing the same length alkyl chain. This study adds new members to liquid crystal whose central core is a flexible ring. [ABSTRACT FROM AUTHOR]

Temperature measurement and control has an extremely important role in both scientific research and manufacturing. Capacitive liquid crystal (LC) temperature sensors can monitor the temperature using the linear variation of the capacitance of LC cell with temperature, but the sensitivity and other properties need to be improved. In order to improve the performance of capacitive LC temperature sensor, we propose to mix twisted nematic LC (1M10600-100) with ferromagnetic nanoparticles γ-Fe2O3 to prepare LC temperature sensor in this paper. The relationship between the capacitance change rate of different concentrations of nano-doped LC materials at 0.1–20 V and different temperatures was tested, the sensitivity of the sensor was calculated, and the mechanism of the effect of doped nanoparticles on the performance of the device was analyzed. The experimental results show that the sensitivity of the capacitive temperature sensor made of nano-doped LC with the concentration of 0.03 wt% is as high as 9.5 pF/°C at 12 V, which is about 14.87% higher than the undoped device, and its recovery and stability remain almost unchanged. The Pearson correlation coefficient only changes by 0.02%. The results of this paper provide some guidance for the improvement of the performance of capacitive LC temperature sensors, and the development of high-sensitivity temperature sensors based on LC materials. [ABSTRACT FROM AUTHOR]

Novel thermochromism is identified in hydrogen bond liquid crystal (HBLC) homologues series which is prepared from non-mesogenic Homophthalic acid (HPA) and mesogenic 4-n-alkyloxybenzoic acid (nOBA, n = 6 to 12). The occurrence of intermolecular interaction between HPA and nOBA, is confirmed by Fourier-transform infrared spectroscopic (FT-IR) technique and computation (DFT) methods. Thermochromic changes in nematic phase and thermo-optic properties of HPA + nOBA HBLC complex is investigated by polarizing optical microscope (POM) and differential scanning calorimetric (DSC) studies. The induced thermochromism in nematic phase which establish the possibility of temperature dependent sensor applications. [ABSTRACT FROM AUTHOR]

The photorefractive effect of flexoelectric smectic liquid crystal blends was investigated. Smectic liquid crystal blends, composed of smectic-C liquid crystals, photoconductive chiral compounds and a sensitizer, are known to exhibit a large photorefractive effect. The chiral compound plays a critical role in the exhibition of large photorefractivity in smectic liquid crystals. The concentration of the chiral compound was varied and the photorefractive properties of the liquid crystal blend were examined. It was found that smectic-C liquid crystals containing small amounts of a chiral compound show a large photorefractivity even though they do not possess spontaneous polarizations. [ABSTRACT FROM AUTHOR]

Graphene quantum dots (GQDs) with a large specific surface area, wide emission spectrum, and low toxicity are advantageous for biomedical and optoelectronic applications. Here, we present a facile method to simultaneously provide ultrafast electro-optical switching and strong vertical anchoring of liquid crystals (LCs) using interfacial self-assembly between alkylated GQDs and polyimide (PI) layers in a closed LC device. The newly fabricated self-assembled PI layer with alkylated GQDs were simply fabricated by doping GQDs into the LC medium, and induced a stable and uniform homeotropic alignment of LCs. Moreover, this self-assembled layer provided a superfast switching speed for the device. [ABSTRACT FROM AUTHOR]

A new type of photoluminescent liquid crystal (LC) device based on a thin layer of CdSe quantum dots (QDs) was proposed to simultaneously offer photoluminescence and fast response time. A thin layer of CdSe QDs was spin-coated on an indium tin oxide electrode as the bottom of the polyimide (PI) alignment layer. This can provide the PI layer with vertical topographic effect, strongly anchoring the LC molecules to the alignment layer. The high anchoring force of the LC device afforded a rapidly falling response time. Furthermore, the CdSe QD layer enabled the device to exhibit photoluminescence under UV irradiation. [ABSTRACT FROM AUTHOR]

In cholesteric liquid crystal (CLC) electrolyte solution, polythiophene was synthesized, and the α-quaterthiophene as a monomer was pre-aligned in a liquid crystal orientation because of its rigidity. The polymer obtained through electrochemical polymerization transferred into the single-handed helical structure of the CLC to assume the form of an atropisomer, and the polymer oriented to the magnetic field was obtained by synthesis under a magnetic field. Electric field-driven control of optical rotation is a function similar to Faraday and Kerr rotations in the polymer. Electrochemical doping can also be used to control the chirality of this polymer. [ABSTRACT FROM AUTHOR]