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Global warming is becoming a more and more severe crisis for humans. One way to resolve the concern is to reduce energy consumption. Smart switchable windows for office and residential buildings and vehicles can help reduce energy consumption. An ideal smart window should be able to control radiant energy flow and privacy. We investigated the capability of switchable windows based on liquid crystal/polymer composites, such as polymer dispersed liquid crystal (PDLC), polymer stabilized liquid crystal (PSLC), and polymer stabilized cholesteric texture (PSCT), to control the privacy and radiant energy flow. Through a systematic study, we identified methods to improve their capabilities. We demonstrated that PDLC and PSCT windows of sufficient thick film thickness can control both privacy and energy flow.

Spiropyran-based materials (SPBMs) can give responses to the stimulations induced by the light, heat, force, or pH, which have been used as triggers for many smart materials. Here, a cross-linkable SPBM containing mesogenic-units is synthesized, which is pale-colored, non-photoluminescent and non-mesogenic at a spiro form, but dark-colored, photoluminescent, and mesogenic at a merocyanine form. Moreover, the dynamic interconversion behavior of the form in the different chemical environments are distinct. Liquid crystalline polymers (LCPs) containing the SPBMs cross-linked via visible light, own a photoswitchable glass transition temperature (Tg ) and retain the switchable property; however, the SPBMs cross-linked via UV light will be locked at the MC state, because the molecular movement was frozen at the room temperature lower than the given Tg of the LCP. Thus, programmable chromism and photoluminescence based on the tunable Tg can be endowed to the functional materials prepared from the SPBMs.

Twist-bend nematic liquid crystals (N_{TB} LCs), although consisting of achiral molecules, possess a spontaneous conic helix. They have been intensively studied and utilized in many applications in recent years. Herein we add chiral molecules to N_{TB} LCs and study their effects on the structure of the conic helix. We observe that the system is in the regular chiral nematic phase at high temperature and is still in the twist-bend nematic phase at low temperature. The addition of the chiral molecules does not induce a twist of the conic helical axis. The main effect of the chiral molecules is increasing the cone angle of the conic helix. We show that the structural chirality parameters in the chiral nematic phase and the twist-bend chiral nematic phase can be calculated from the same intrinsic chirality parameter, which only depends on the molecular structure and concentrations of the chiral molecule. We also observe a pretransitional phenomenon that the helical pitch of the chiral nematic phase increases dramatically when temperature is decreased toward the chiral nematic to twist-bend nematic phase transition temperature.

This contribution investigates the preparation of polymer-dispersed liquid crystal (PDLC) films based on meth(acrylate) monomers containing rigid structures. The current study specifically focuses ...

Fabricating functional materials via molecular self-assembly is a promising approach, and precisely controlling the molecular building blocks of nanostructures in the self-assembly process is an essential and challenging task. Blue phase liquid crystals are fascinating self-assembled three-dimensional nanomaterials because of their potential information displays and tuneable photonic applications. However, one of the main obstacles to their applications is their narrow temperature range of a few degrees centigrade, although many prior studies have broadened it to tens via molecular design. In this work, a series of tailored uniaxial rodlike mesogens disfavouring the formation of blue phases are introduced into a blue phase system comprising biaxial dimeric mesogens, a blue phase is observed continuously over a temperature range of 280 °C, and the range remains over 132.0 °C after excluding the frozen glassy state. The findings show that the molecular synergistic self-assembly behavior of biaxial and uniaxial mesogens may play a crucial role in achieving the ultrastable three-dimensional nanostructure of blue phases., Blue phases are spatially ordered yet fragile liquid crystalline structures, bearing applications in optoelectronics and photonics. Hu et al. show that self-assembly within a mixture of different mesogens may significantly broaden the temperature range over which they are stable.

We report a novel polymer stabilized liquid crystal based light waveguide display whose performance is significantly improved by using patterned photo-polymerization or an electrode. The waveguide display is edge-lit and operates on the light scattering of the polymer stabilized liquid crystal. When no voltage is applied, the liquid crystal is uniformly aligned and is transparent. The incident light is waveguided through the display by total internal reflection and no light comes out of the viewing side of the display. When a voltage is applied, the liquid crystal is switched to a micron-sized poly-domain structure and becomes scattering. The incident light is scattered out of the viewing side of the display. We demonstrated that by using patterned photo-polymerization or an ITO electrode, the scattering efficiency of the liquid crystal in the voltage-on state is significantly enhanced. We have achieved high brightness, low driving voltage, sub-millisecond switching time and high contrast ratio. This new display is suitable for transparent and augmented display applications.

Chirality is of great importance in physical and biological systems. It helps differentiate chemical reactions and physical processes. It was reported that the diffusion of mesogenic chiral guests in chiral nematic liquid crystal hosts profoundly depends on the chirality of the guest and host molecules. When the guest and host molecules have the same handedness, the diffusion is much faster than that when the guest and host molecules have the opposite handedness. In this paper, we report the discovery that chiral differentiation also exists in the diffusion of limonene, which is non-mesogenic in chiral nematic liquid crystals. The diffusion of l-limonene (right-handed) in chiral nematic liquid crystals with a right handed helical structure is faster than that of d-limonene (left-handed). This result might be important in understanding the effects of chirality on physical processes that take place in biological systems. In addition, this effect could be utilized for enantiomer separation in the pharmaceutical industry.

The photonic band gap of cholesteric liquid crystal with negative dielectric anisotropies can be broadened under DC electric voltages by polymer stabilization. The broadening is produced by the movement and aligning effect of the dispersed “structural” chiral polymer network. We carried out a systematic study of factors, such as the alignment layer, moisture and ionic additives, which affect the broadening. Our experimental results show that the degree of broadening is strongly dependent on the ion concentration in the polymer stabilized cholesteric liquid crystal. We observed a linear relation between the broadening and the ion density. By using the optimal material formulation, we achieve 3 folds broadening to cover the entire visible light region with low voltages.

Quantum dots (QDs) have been used to make backlight, which provides a superior color gamut, for liquid crystal flat panel displays. In the backlight system, quantum dots, embedded in a polymer film and illuminated by blue light, emit red and green light with narrow bandwidths. There is, however, a problem with the system in that the quantum dots emit light in all directions, and most of the emitted light is in directions with large incident angles and cannot exit the film due to the total internal reflection at the film-air interface and is wasted. We propose to use an aligned polymer dispersed liquid crystal (APDLC) film to reduce the total internal reflection in the QD backlight and thus improve the light efficiency. A regular PDLC film, where the embedded liquid crystal droplets are randomly oriented, exhibits isotropic scattering and is not a good candidate for the enhancement of light efficiency of QD backlight. Through a two-step polymerization, we successfully developed an aligned polymer dispersed liquid crystal (APDLC) film where the liquid crystal droplets are permanently unidirectionally aligned in the film’s normal direction. It exhibits selective scattering: it scatters light with large incident angles but not light with small incident angles. When the APDLC film is laminated on the QD backlight film, a significant enhancement of the light efficiency of the QD backlight is achieved. The APDLC film can also be used to increase the light efficiency of other flat panel displays, such as organic light emitting diode (OLED) display and micro-light emitting diode (MLED) display.

Aim: To investigate the clinical relevance and functional role of HOXA13 in prostate cancer Methods: PCR, western blot and immunohistochemistry were performed to determine the expression. Kaplan-Meier and Cox regression survival analyses investigated the clinical relevance. Cell viability, flow cytometry and transwell assays were used to determine the functional roles. Results: HOXA13 expression is sharply increased in carcinoma tissues and is significantly associated with poor prognosis of prostate cancer patients. Interestingly, nucleus not cytoplasm HOXA13 expression is associated with unfavorable survival of the patients. Furthermore, nucleus HOXA13 expression represents an unfavorable and independent prognosis factor of histological grade 2 or Gleason grade

Liquid crystal (LC) droplets dispersed in isotropic media are of significant interest for scientific community and great importance for industries. The confinement can generate many fascinating LC ...

The reflection band of polymer stabilized cholesteric liquid crystals with negative dielectric anisotropy can be broadened by DC electric fields, which was ascribed to the pitch gradient caused by the motion of the structural chirality, that is, the polymer network. They systematically varied the mixture components, such as the photo-initiator concentration, the monomer functionality, and the chiral dopant, to explore their influences on the reflection band broadening behavior. They learned how to control the polymer network morphology and ion density, which in turn determined the reflection bandwidth. By optimizing the mixture, they have greatly enhanced the broadening effect and achieved large bandwidth at low voltages. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017

Now you see me\dots{} This article reports a switchable liquid-crystal smart window that can be independently operated in two voltage-modulated modes. In the first mode, for privacy control, the window is switched between a transparent state and a scattering state by a low-frequency voltage, based on flexoelectric interaction; in the second, for energy-flow control, it is switched between transparent and absorbing states by a high-frequency voltage, based on dielectric interaction. This technology ought to be very useful for both architectural and automobile windows.

Self-assembly of colloids into superstructures is very important for fabricating functional devices. This study demonstrates that in a colloidal system of anisotropic liquid-crystal droplets dispersed in isotropic glycerol, the droplets self-assemble into periodic superstructures in cells with patterned indium tin oxide (ITO) electrodes, due to the different surface tensions of the two components on ITO and glass. This self-assembly of the liquid-crystal droplets may be utilized to manufacture $e.g.$ switchable photonic crystals, sensors, or microlens arrays.

Liquid crystal displays are the leading technology for flat panel displays. Their energy efficiency is low, however, due to the light absorption caused by polarizers and color filters and power consumption by driving circuitries. In displaying static images, their energy efficiency can be improved if a low driving frequency is used. As the driving frequency is decreased, the transmittance of the displays may change with time, a phenomenon known as image flickering. In this research we demonstrated that polymer stabilization can significantly reduce the flickering in fringe field switching (FFS) liquid crystal display. Under the polymer stabilization, the driving voltage remains low and the response time becomes shorter. Through simulation study, we find that the polymer stabilization smooths the spatial variation of the liquid crystal orientation in the display, and thus reduce the flexoelectric effect which is responsible for image flickering. The polymer stabilization can be implemented in the current main stream manufacturing to produce displays that can show static images under low power consumption.

Cholesteric liquid crystals consist of chiral rod-like molecules which self-assemble into a helical structure. The molecules twist periodically along an axis which is orthogonal to the long molecular axis. For cholesteric liquid crystals with a helical pitch comparable to the wavelength of visible light, they Bragg reflect light. In this chapter we discuss polymer-stabilized cholesteric liquid crystals where polymer networks are dispersed in the liquid crystals to control the electro-optical properties of the liquid crystals. The reflection of the polymer-stabilized cholesteric liquid crystals can be tuned by applying electric voltages. The materials are of great practical importance and can be used in many applications such as reflective displays, writing tablets, tuneable color filters and tuneable mirror-less lasers.

Cholesteric liquid crystals (hereafter Ch LCs) are self-assembled systems consisting of elongated chiral organic molecules. They possess a helical structure where the local average direction of the molecules twists spatially around an orthogonal helical axis. Their refractive index varies periodically, and thus exhibits a Bragg reflection band centered at the wavelength λ = [(ne + no)/2]P and with the bandwidth Δλ = (ne - no)P, where ne and no are the extraordinary and ordinary refractive indices of the LC, respectively, and P is the helical pitch. They can be used to make reflective displays which do not need polarizers and have high reflectance. In this chapter, various mechanisms, which can be used to modify the reflection of the displays, are described. The performance of the displays is also discussed.

Global warming, due to the consumption of fossil energy, is one of the biggest challenges in recent days. Air conditioning (cooling and heating) of office and residential buildings is one of the largest energy consumptions. One way to reduce the energy consumption is to use switchable architectural windows, which can control radiant energy flow. Herein, a smart thermally switchable window with transmittance sensitive to ambient temperature is reported. This smart window is based on a liquid crystal (LC) whose orientation varies with temperature. At temperatures lower than a low threshold temperature, such as in winter, the LC orients perpendicular to the window substrate, and the window is transparent and lets sunlight pass it to warm interiors of buildings. At temperatures higher than a high threshold temperature, such as in summer, the LC orients parallel to the substrate. The window becomes absorbing and blocks sunlight, resulting in a reduction of the solar heating. When temperature varies between these two thresholds, the window has gray‐level transmittances. It does not use electricity and is very energy‐saving, and has an immense potential in applications of smart architectural and vehicle windows.

A novel series of dichroic anthraquinone dyes have been successfully synthesised with conventional Sonogashira reaction. These synthesised anthraquinone dyes were found to have high dichroic ratios, good solubilities, excellent hues and to be potential candidates for guest–host liquid crystal displays. The dichroic ratio is as high as 13.26, which is in the top level of the anthraquinone dyes reported so far. In addition, this paper provides an effective method to modulate the optic properties of anthraquinone dyes from the molecular level via the introduction of different radicals on the anthraquinone cores.

An electrochromic liquid crystal (ECLC) material composed of only liquid crystal (LC) and ionic liquid (IL) was developed. The LC containing the substituted diphenylacetylene serves as electrochromic (EC) material to realise transmittance and colour change under the direct current (DC) field, while the IL with the designable cation and anion served as electrolyte. Herein, a series of IL electrolytes was screened to investigate how IL tunes the electro-optic performance of the ECLC cell. By testing the electrochemistry window of ILs in EC cells, IL with the [NTf2]− anion shows adequate electrochemical stability when the EC material undergoes oxidation and reduction. The electro-optic performance of ECLC containing 1-ethoxy-4-[2-(4-pentylphenyl) ethynyl]-benzene (PEB) and IL was then evaluated by UV-vis spectrometry under the control of an electrochemical work station. Compared with other PEB-IL, PEB-[Bmim][NTf2] with [Bmim][NTf2] electrolyte shows a satisfactory transmittance at low operating voltage. Furthermore, Pd NPs in situ formed in [Bmim][NTf2] reduced the EC potential and improved the light scattering of the ECLC cell. In this work, we also designed a bifunctional device based on polymer dispersed liquid crystal (PDLC) that hosts electrochromic guest molecules, and analysed the electro-optical and electrochromic properties of LC electrolyte mixtures, in order to gain control of the incident daylight and glare in building and automotive applications.

A polymeric liquid crystalline film was fabricated by photo-induced diffusion and mesogenic phase structural transition of photopolymerisable acrylate monomer mixtures that presented phase transition between cholesteric (Ch) and smectic (SmA) phases. By controlling the curing temperature to be close to SmA–Ch phase transition, a novel architecture that combined Ch and SmA-like short-range ordering (SSO) nanostructures was obtained, which reflected light with the wavelength from 0.5 to 11.5 µm. Experimental results showed that the existence of UV-absorbing dye and curing temperature were critical for the creation of asymmetrical super wide pitch gradient distribution. Moreover, the reflection wavelength and bandwidth of the cholesteric liquid crystal (CLC) films were tuneable by adjusting proportion of the compounds, and the bandwidth could be broadened up to 13 μm. It was expected to have great potential applications in fields like architectural energy conservation or infrared-stealth.

Liquid crystals have been used to make electrically switchable light shutters (windows), but most of them are monostable: opaque in the absence of applied voltage and transparent when a voltage is applied. Here we report a bistable switchable light shutter based on cholesteric liquid crystal doped with tetrabutylammonium bromide. The salt makes it possible for the liquid crystal to have different electro-optical responses to applied voltages with different frequencies. The shutter can be either transparent or opaque in the absence of applied voltage. It can be switched from the transparent state to the opaque state by applying a low frequency (60 Hz) voltage pulse and switched back to the transparent state by applying a high frequency (2 kHz) voltage pulse. Because of the bistability, it can be used for energy-saving switchable privacy control and architectural windows.

A series of polysiloxane side chain liquid crystal polymers (PSCLCPs) with chiral and achiral substitutions in the side chains, denoted as PMMS-Xchol-n (n = 0, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5 0.6, 0.7. 0.8, 0.9, and 1.0, respectively, the molar content of the chiral cholesteric unit (Xchol) in a specific polymer), were successfully synthesized via thiol–ene click chemistry. The molecular structures of the polymers were confirmed by 1H-NMR, FT-IR, gel permeation chromatography (GPC) and thermogravimetric analysis (TGA). Their liquid crystalline (LC) properties and self-assembling behaviors were investigated in detail by a combination of various techniques, such as differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-ray diffraction. The results demonstrated that the phase transition behaviour and the self-assembly structure of the polymers were significantly influenced by Xchol and temperatures. With increased Xchol, the clearing points increased significantly, their mesogenic temperature ranges greatly widened, and abundant mesophases developed. Generally, two different types of LC phase structures and three different molecular arrangements were observed, depending on the two LC building blocks. Polymers with Xchol below 0.3 could self-assemble into a smectic E (SmE)-like structure and a single layer smectic A (SmAs) structure upon heating. When Xchol was between 0.4 and 0.7, a single phase structure of a SmAs or a bilayer smectic A (SmAd) could be observed. While for polymers with Xchol over 0.8, a SmAd phase structure was self-organized, further heating led to a SmAs structure. Moreover, when the molar ratio of the chiral group or achiral group was about 0.1, a microphase-separated smectic morphology could be found, indicating that the introduction of a small amount of any components in the copolymers might destroy the well-ordered structures.

Chiral nematic liquid crystals possess a self-assembled helical structure and exhibit unique selective reflection in visible and infrared light regions. Their optical properties can be electrically tuned. The tuning involves the unwinding and restoring of the helical structure. We carried out an experimental study on the mechanism of the restoration of the helical structure. We constructed chiral nematic liquid crystals with variable elastic constants by doping bent-dimers and studied their impact on the restoration. With matched twist and bend elastic constants, the helical structure can be restored dramatically fast from the field-induced homeotropic state. Furthermore, defects can be eliminated to produce a perfect planar state which exhibits high selective reflection.

It was discovered recently that liquid crystal dimers with a flexible central linkage with an odd number of carbons, such as CB7CB, have bent molecular shapes and have anomalously small bend elastic constants. When such a dimer is doped into regular liquid crystals, it can greatly modify the properties of the hosts and can enable novel structures and electro-optical properties. We doped CB7CB to a regular thermotropic nematic liquid crystal and then dispersed the material in isotropic polymer with tangential anchoring condition, we obtained toroidal liquid crystal droplets, which was only realized before for lyotropic liquid crystals. When we doped CB7CB to a regular cholesteric liquid crystal, we obtained perfect planar state without any oily streak defects. Also by doping CB7CB to a cholesteric liquid crystal, we achieved stable Helfrich deformation and reflection color tuning under low driving voltages.

Biaxiality and chirality are two of the most interesting topics in materials and biological science, particularly in liquid crystals. What is even more interesting is that these two properties are related. It was theoretically predicted that morphological chirality is impossible without morphological biaxiality in chiral nematic liquid crystals. We experimentally study the effect of biaxiality on chirality. We show that when achiral liquid crystal dimers with large molecular biaxiality are doped into chiral nematic liquid crystals, their helical pitch is significantly decreased. We have also observed an abnormal fingerprint texture of the chiral nematic liquid crystal doped dimers, which suggests morphological biaxiality. Our experimental results support the biaxial theory of chiral nematic liquid crystals.