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Showing papers on "Liquid crystal published in 2018"


Journal ArticleDOI
TL;DR: In this article, the design and additive manufacturing of LCE actuators (LCEAs) with spatially programed nematic order that exhibit large, reversible, and repeatable contraction with high specific work capacity are reported.
Abstract: Liquid crystal elastomers (LCEs) are soft materials capable of large, reversible shape changes, which may find potential application as artificial muscles, soft robots, and dynamic functional architectures. Here, the design and additive manufacturing of LCE actuators (LCEAs) with spatially programed nematic order that exhibit large, reversible, and repeatable contraction with high specific work capacity are reported. First, a photopolymerizable, solvent-free, main-chain LCE ink is created via aza-Michael addition with the appropriate viscoelastic properties for 3D printing. Next, high operating temperature direct ink writing of LCE inks is used to align their mesogen domains along the direction of the print path. To demonstrate the power of this additive manufacturing approach, shape-morphing LCEA architectures are fabricated, which undergo reversible planar-to-3D and 3D-to-3D' transformations on demand, that can lift significantly more weight than other LCEAs reported to date.

431 citations


Journal ArticleDOI
TL;DR: This Review presents recent advances of liquid crystals that should contribute to the next generation of materials.
Abstract: Since the discovery of the liquid-crystalline state in 1888, liquid crystal science has made great advances through fusion with various technologies and disciplines. Recently, new molecular design strategies and new self-assembled structures have been developed as a result of the progress made in synthetic procedures and characterization techniques. Since these liquid crystals exhibit new functions and properties derived from their nanostructures and alignment, a variety of new functions for liquid crystals, such as transport for energy applications, separation for environmental applications, chromism, sensing, electrooptical effects, actuation, and templating have been proposed. This Review presents recent advances of liquid crystals that should contribute to the next generation of materials.

307 citations


Journal ArticleDOI
TL;DR: In this article, the authors demonstrate the dynamic switching of beam deflection by a silicon-nanodisk dielectric metasurface infiltrated with liquid crystals, and show the switching of a laser beam from 0° to a 12° angle with an efficiency of 50% by heating the metasuran surface to modify the liquid crystal state from nematic to isotropic.
Abstract: Dynamic steering of laser beams by ultrathin optical metasurfaces is a significant research advance for possible applications in remote ranging and sensing. A unique platform for such important functionalities is offered by dielectric metasurfaces that have the highest transmission efficiency. However, the realization of dynamically tunable metasurfaces still remains a challenge. Here we experimentally demonstrate the dynamic switching of beam deflection by a silicon-nanodisk dielectric metasurface infiltrated with liquid crystals. In particular, we show the switching of a laser beam from 0° to a 12° angle with an efficiency of 50% by heating the metasurface to modify the liquid crystal state from nematic to isotropic. Our results open important opportunities for tunable ultrathin beam steering metadevices.

244 citations


Journal ArticleDOI
TL;DR: In this article, a pedagogical overview of liquid crystals is presented based on lectures for postgraduate students given at the International Max Planck Research School "Modeling of Soft Matter".

227 citations


Journal ArticleDOI
TL;DR: A facile approach is demonstrated to enhance the out-of-plane work capacity of LCE materials by an order of magnitude, to nearly 20 J/kg.
Abstract: Liquid crystalline elastomers (LCEs) are soft, anisotropic materials that exhibit large shape transformations when subjected to various stimuli. Here we demonstrate a facile approach to enhance the out-of-plane work capacity of these materials by an order of magnitude, to nearly 20 J/kg. The enhancement in force output is enabled by the development of a room temperature polymerizable composition used both to prepare individual films, organized via directed self-assembly to retain arrays of topological defect profiles, as well as act as an adhesive to combine the LCE layers. The material actuator is shown to displace a load >2500× heavier than its own weight nearly 0.5 mm.

151 citations


Journal ArticleDOI
TL;DR: Achlioptas et al. as mentioned in this paper reported a series of achiral asymmetric dimers with an odd number of atoms in the spacer, which formed twisted structures in nematic as well as in lamellar phases.
Abstract: Chiral symmetry breaking in soft matter is a hot topic of current research. Recently, such a phenomenon was found in a fluidic phase showing orientational order of molecules-the nematic phase; although built of achiral molecules, the phase can exhibit structural chirality-average molecular direction follows a short-pitch helix. Here, we report a series of achiral asymmetric dimers with an odd number of atoms in the spacer, which form twisted structures in nematic as well as in lamellar phases. The tight pitch heliconical nematic (NTB) phase and heliconical tilted smectic C (SmCTB) phase are formed. The formation of a variety of helical structures is accompanied by a gradual freezing of molecular rotation. In the lowest temperature smectic phase, HexI, the twist is expressed through the formation of hierarchical structure: nanoscale helices and mesoscopic helical filaments. The short-pitch helical structure in the smectic phases is confirmed by resonant X-ray measurements.

149 citations


Journal ArticleDOI
TL;DR: A review of the state of the art in this fast-growing field, with a focus on its scientif... as mentioned in this paper, can be found in Section 5.1.1].
Abstract: Colloids are abundant in nature, science, and technology, with examples ranging from milk to quantum dots and the colloidal atom paradigm. Similarly, liquid crystal ordering is important in contexts ranging from biological membranes to laboratory models of cosmic strings and liquid crystal displays in consumer devices. Some of the most exciting recent developments in both of these soft matter fields emerge at their interface, in the fast-growing research arena of liquid crystal colloids. Mesoscale self-assembly in such systems may lead to artificial materials and to structures with emergent physical behavior arising from patterning of molecular order and nano- or microparticles into precisely controlled configurations. Liquid crystal colloids show exceptional promise for new discovery that may impinge on composite material fabrication, low-dimensional topology, photonics, and so on. Starting from physical underpinnings, I review the state of the art in this fast-growing field, with a focus on its scientif...

131 citations



Journal ArticleDOI
TL;DR: A review of photothermally driven liquid crystal actuators can be found in this article, where the authors discuss the advantages of using the photothermal effect and the possibilities of actuator designs.
Abstract: Liquid crystal polymers (LCPs) have emerged as a material of choice for soft actuators, for which applications have been envisioned in many areas. In contrast to the actuators based on polymer hydrogels whose reversible volume or size change relies on absorption and release of water molecules by the polymer related to a thermal phase transition of the polymer solution, LCPs exhibit macroscopic shape change as a result of LC–isotropic, or order–disorder, phase transition of the mesogens that are part of the polymer structure either in the main chain or as side groups. LCP actuators, in the form of a crosslinked network, can be triggered by various stimuli such as change in temperature, change in humidity, light and electric power. Of these, light is a particularly attractive stimulus owing to the attributes of remote, localized or patterned activation. Until now, the large majority of light-triggered LCP actuators, generally referred to as liquid crystal elastomers (LCEs) or liquid crystal networks (LCNs), are azobenzene-containing polymers, for which the order–disorder phase transition of the azobenzene mesogens is induced by the reversible trans–cis photoisomerization of the chromophore. In recent years, however, there has been growing interest in photocontrolled LCP actuators that involve no photochemical reactions but use simply a photothermal effect to control the order–disorder phase transition. This review is focused on such photothermally driven LCP actuators. Highlighted are examples of reported studies demonstrating the actuation modes and possible applications. We also discuss the advantages of using the photothermal effect and the possibilities of actuator designs. At the end, we provide an outlook for the development of this type of polymer actuator in the near future.

121 citations


Journal ArticleDOI
TL;DR: In this review, the current understanding of the structure-property relationship of graphene oxide liquid crystals (GOLCs) is overviewed, and various interesting applications of GOLCs are outlined together with the future prospects for their further developments.
Abstract: Graphene, despite being the best known strong and electrical/thermal conductive material, has found limited success in practical applications, mostly due to difficulties in the formation of desired large-scale highly organized structures. Our discovery of a liquid crystalline phase formation in graphene oxide dispersion has enabled a broad spectrum of highly aligned graphene-based structures, including films, fibers, membranes, and mesoscale structures. In this review, the current understanding of the structure-property relationship of graphene oxide liquid crystals (GOLCs) is overviewed. Various synthetic methods and parameters that can be optimized for GOLC phase formation are highlighted. Along with the results from different characterization methods for the identification of the GOLC phases, the typical characteristics of different types of GOLC phases introduced so far, including nematic, lamellar and chiral phases, are carefully discussed. Finally, various interesting applications of GOLCs are outlined together with the future prospects for their further developments.

115 citations


Journal ArticleDOI
TL;DR: The synthesis and characterization of a novel halogen-bonded light-driven axially chiral molecular switch that is able to induce a self-organized, tunable helical superstructure when doped into an achiral liquid crystal (LC) host is reported.
Abstract: Supramolecular approaches toward the fabrication of functional materials and systems have been an enabling endeavor. Recently, halogen bonding has been harnessed as a promising supramolecular tool. Herein we report the synthesis and characterization of a novel halogen-bonded light-driven axially chiral molecular switch. The photoactive halogen-bonded chiral switch is able to induce a self-organized, tunable helical superstructure, that is, cholesteric liquid crystal (CLC), when doped into an achiral liquid crystal (LC) host. The halogen-bonded switch as a chiral dopant has a high helical twisting power (HTP) and shows a large change of its HTP upon photoisomerization. This light-driven dynamic modulation enables reversible selective reflection color tuning across the entire visible spectrum. The chiral switch also displays a temperature-dependent HTP change that enables thermally driven red, green, and blue (RGB) reflection colors in the self-organized helical superstructure.

Journal ArticleDOI
TL;DR: Remarkably, LC functionalized cellulose acetate films were found to be highly efficient in assisting a perfect homeotropic alignment of LCs over the entire area of the LC sample under observation indicating their superior aligning ability in comparison to their unmodified and octadecyltrimethoxysilane (OTS) modified counterparts.
Abstract: A simple and effective approach for vertical alignment of liquid crystals (LCs) over a functionalized transparent flexible substrate is described. Surface characterization of this commercially available plastic substrate through X-ray photoelectron spectroscopy (XPS) and attenuated total reflection infrared spectroscopy (ATR-IR) indicated that cellulose acetate is main component of the transparent substrate. This substrate was chemically functionalized with a suitable LC compound. A trimethoxysilane terminated new rod-shaped mesogen is synthesized and covalently attached to the pre-treated film through silane condensation reaction. LC functionalization of the polymer film is confirmed through contact angle (CA), atomic force microscopy (AFM), XPS and ATR-IR spectroscopy studies. Versatility of the LC modified flexible substrates for the alignment of bulk LC sample at substrate-LC interface was assessed for nematic (N) and smectic A (SmA) phases. Remarkably, LC functionalized cellulose acetate films were found to be highly efficient in assisting a perfect homeotropic alignment of LCs (for both, a room temperature N and a high temperature SmA phase) over the entire area of the LC sample under observation indicating their superior aligning ability in comparison to their unmodified and octadecyltrimethoxysilane (OTS) modified counterparts. The demonstrated method of surface modification of flexible polymer film is easy, surface modified substrates are stable for several months, retained their aligning ability intact and more importantly they are reusable with maximum delivery.

Journal ArticleDOI
TL;DR: The dynamic tuning of spontaneous emission from a Mie-resonant dielectric metasurface that is situated on a fluorescent substrate and embedded into a liquid crystal cell is experimentally demonstrated and is demonstrated to be a viable strategy to realize flat tunable light sources based on dielectrics meetasurfaces.
Abstract: Mie-resonant dielectric metasurfaces offer comprehensive opportunities for the manipulation of light fields with high efficiency. Additionally, various strategies for the dynamic tuning of the optical response of such metasurfaces were demonstrated, making them important candidates for reconfigurable optical devices. However, dynamic control of the light-emission properties of active Mie-resonant dielectric metasurfaces by an external control parameter has not been demonstrated so far. Here, we experimentally demonstrate the dynamic tuning of spontaneous emission from a Mie-resonant dielectric metasurface that is situated on a fluorescent substrate and embedded into a liquid crystal cell. By switching the liquid crystal from the nematic state to the isotropic state via control of the cell temperature, we induce a shift of the spectral position of the metasurface resonances. This results in a change of the local photonic density of states, which, in turn, governs the enhancement of spontaneous emission fro...

Journal ArticleDOI
TL;DR: The discovery of cholesteric phases in amyloids is reported, using β-lactoglobulin fibrils shortened by shear stresses, with confinement-induced transitions from an ordered to an ordered state.
Abstract: Chirality is ubiquitous in nature and plays crucial roles in biology, medicine, physics and materials science. Understanding and controlling chirality is therefore an important research challenge with broad implications. Unlike other chiral colloids, such as nanocellulose or filamentous viruses, amyloid fibrils form nematic phases but appear to miss their twisted form, the cholesteric or chiral nematic phases, despite a well-defined chirality at the single fibril level. Here we report the discovery of cholesteric phases in amyloids, using β-lactoglobulin fibrils shortened by shear stresses. The physical behaviour of these new cholesteric materials exhibits unprecedented structural complexity, with confinement-driven ordering transitions between at least three types of nematic and cholesteric tactoids. We use energy functional theory to rationalize these results and observe a chirality inversion from the left-handed amyloids to right-handed cholesteric droplets. These findings deepen our understanding of cholesteric phases, advancing their use in soft nanotechnology, nanomaterial templating and self-assembly.

Journal ArticleDOI
TL;DR: In this article, the authors formulate the statistical dynamics of topological defects in the active nematic phase, formed in two dimensions by a collection of self-driven particles on a substrate, and derive an interacting particle description of defects that includes active torques.
Abstract: We formulate the statistical dynamics of topological defects in the active nematic phase, formed in two dimensions by a collection of self-driven particles on a substrate. An important consequence of the nonequilibrium drive is the spontaneous motility of strength +1/2 disclinations. Starting from the hydrodynamic equations of active nematics, we derive an interacting particle description of defects that includes active torques. We show that activity, within perturbation theory, lowers the defect-unbinding transition temperature, determining a critical line in the temperature-activity plane that separates the quasi-long-range ordered (nematic) and disordered (isotropic) phases. Below a critical activity, defects remain bound as rotational noise decorrelates the directed dynamics of +1/2 defects, stabilizing the quasi-long-range ordered nematic state. This activity threshold vanishes at low temperature, leading to a reentrant transition. At large enough activity, active forces always exceed thermal ones and the perturbative result fails, suggesting that in this regime activity will always disorder the system. Crucially, rotational diffusion being a two-dimensional phenomenon, defect unbinding cannot be described by a simplified one-dimensional model.

Journal ArticleDOI
TL;DR: The liquid crystalline behaviour of two molecular complexes assembled by hydrogen bonding between a stilbazole-based template and alkoxybenzoic acids has been characterised and exhibit the heliconical twist-bend nematic phase (NTB) over a broad temperature range.

Journal ArticleDOI
TL;DR: In this article, a series of cellulose nanocrystal (CNC)-based nanocomposite materials that mimic the cholesteric structural colored creatures in nature were prepared and their functional applications investigated.
Abstract: Structural colored nanocomposites with photonic liquid crystal structures are desirable owing to their excellent optical performances, unique structural features and intelligent responsive behaviors. Herein, a series of cellulose nanocrystal (CNC)-based nanocomposite materials that mimic the cholesteric structural colored creatures in nature were prepared and their functional applications investigated. Multicolored, flexible and intelligent responsive iridescent films were constructed by mixing cellulose nanocrystals (CNCs) and glycerol (Gly) in different ratios. Consequently, redshifted structural colors were obtained from the increase in the helical pitch of the chiral nematic structures according to the microstructure analysis. In addition to improving the mechanical properties of the composite films, glycerol also promoted the crystallinity of the films to different degrees. The CNC/Gly20 films exhibited reversible reflection colors at different relative humidity because of the strong water absorption capability of glycerol. Furthermore, CNC/Gly composite suspensions were used as photonic inks to obtain photonic writing with unique fingerprint textures. Moreover, the CNC/Gly nanocomposites were also used to make iridescent coatings on different substrates. The incorporation of glycerol improved the compatibility between the interfaces. Thus, photonic nanocomposites from cellulose nanocrystals can potentially be developed as optical sensors, security markings and functional coatings.

Journal ArticleDOI
TL;DR: The continuum model, which couples structure and hydrodynamics, is able to capture the annihilation and movement of defects over long time scales, and is demonstrated to predict not only the static structure of the material, including its topological defects, but also the evolution of the system into dynamically arrested states.
Abstract: Achieving control and tunability of lyotropic materials has been a long-standing goal of liquid crystal research. Here we show that the elasticity of a liquid crystal system consisting of a dense suspension of semiflexible biopolymers can be manipulated over a relatively wide range of elastic moduli. Specifically, thin films of actin filaments are assembled at an oil-water interface. At sufficiently high concentrations, one observes the formation of a nematic phase riddled with [Formula: see text] topological defects, characteristic of a two-dimensional nematic system. As the average filament length increases, the defect morphology transitions from a U shape into a V shape, indicating the relative increase of the material's bend over splay modulus. Furthermore, through the sparse addition of rigid microtubule filaments, one can gain additional control over the liquid crystal's elasticity. We show how the material's bend constant can be raised linearly as a function of microtubule filament density, and present a simple means to extract absolute values of the elastic moduli from purely optical observations. Finally, we demonstrate that it is possible to predict not only the static structure of the material, including its topological defects, but also the evolution of the system into dynamically arrested states. Despite the nonequilibrium nature of the system, our continuum model, which couples structure and hydrodynamics, is able to capture the annihilation and movement of defects over long time scales. Thus, we have experimentally realized a lyotropic liquid crystal system that can be truly engineered, with tunable mechanical properties, and a theoretical framework to capture its structure, mechanics, and dynamics.

Journal ArticleDOI
TL;DR: A review of the characteristics of different structures of liquid crystalline phases, the influencing factors on the phase transition of liquid crystals and the relationship between structures of LLC and drug diffusion is given in this article.
Abstract: Lyotropic liquid crystals (LLCs) formed by the self-assembly of amphiphilic molecules in a solvent (usually water) have attracted increasingly greater attention in the last few decades, especially the lamellar phase (Lα), the reversed bicontinuous cubic phase (Q2) and the reversed hexagonal phase (H2). Such phases offer promising prospects for encapsulation of a wide range of target molecules with various sizes and polarities owing to the unique internal structures. Also, different structures of mesophases can give rise to different diffusion coefficients. The bicontinuous cubic phase and the hexagonal phase have been demonstrated to control and sustain the release of active molecules. Furthermore, the structures are susceptible to many factors such as water content, temperature, pH, the presence of additives etc. Many researchers have been studying these influencing factors in order to accurately fabricate the desired phase. In this paper, we give a review of the characteristics of different structures of liquid crystalline phases, the influencing factors on the phase transition of liquid crystals and the relationship between structures of LLC and drug diffusion. We hope our review will provide some insights into how to manipulate in a controlled manner the rate of incorporating and transferring molecules by altering the structure of lyotropic mesophases.

Journal ArticleDOI
TL;DR: A review of the history and recent advances in the synthesis and corresponding photomechanical response of these materials can be found in this paper, with a focus on the use of azobenzene as either a guest additive or covalently attached to the network.
Abstract: Liquid crystals are widely employed as stimuli-responsive materials Liquid crystallinity can be retained in polymeric form Photoinduced mechanical effects in liquid crystalline polymer networks and elastomers have been a topic of considerable recent research This review details the historical underpinnings and recent advances in the synthesis and the corresponding photomechanical response of these materials In nearly all cases, the conversion of light into mechanical work has employed azobenzene as either a guest additive or covalently attached to the network © 2018 Wiley Periodicals, Inc J Polym Sci, Part B: Polym Phys 2018

Journal ArticleDOI
TL;DR: In the recent two decades liquid crystal science has contributed significantly to the understanding of mirror symmetry breaking and spontaneous emergence of chirality in fluids as mentioned in this paper, which has led to the development of a new understanding of the structure of the crystal lattice.
Abstract: In the recent two decades liquid crystal science has contributed significantly to the understanding of mirror symmetry breaking and spontaneous emergence of chirality in fluids This accoun

Journal ArticleDOI
TL;DR: A supramolecular system in which the emergence of oscillating patterns is encoded at the molecular level, which comprises chiral liquid crystal structures that revolve continuously when illuminated, under the action of embedded light-driven molecular motors.
Abstract: Molecular machines operated by light have been recently shown to be able to produce oriented motion at the molecular scale 1,2 as well as do macroscopic work when embedded in supramolecular structures 3–5. However, any supramolecular movement irremediably ceases as soon as the concentration of the interconverting molecular motors or switches reaches a photo-stationary state 6,7. To circumvent this limitation, researchers have typically relied on establishing oscillating illumination conditions—either by modulating the source intensity 8,9 or by using bespoke illumination arrangements 10–13. In contrast, here we report a supramolecular system in which the emergence of oscillating patterns is encoded at the molecular level. Our system comprises chiral liquid crystal structures that revolve continuously when illuminated, under the action of embedded light-driven molecular motors. The rotation at the supramolecular level is sustained by the diffusion of the motors away from a localized illumination area. Above a critical irradiation power, we observe a spontaneous symmetry breaking that dictates the directionality of the supramolecular rotation. The interplay between the twist of the supramolecu-lar structure and the diffusion 14 of the chiral molecular motors creates continuous, regular and unidirectional rotation of the liquid crystal structure under non-equilibrium conditions.

Journal ArticleDOI
TL;DR: The first 10 homologues of CB6O were synthesized and characterised in this article, all of which exhibit nematological properties similar to those of CB2Om.
Abstract: The syntheses and characterisation of the first 10 homologues of the 1-(4-cyanobiphenyl-4′-yl)-6-(4-alkyloxyanilinebenzylidene-4′-oxy)hexanes (CB6O.Om) are reported. All 10 homologues exhibit nemat...

Journal ArticleDOI
16 Jan 2018-Langmuir
TL;DR: It is shown that an intermediate stage of self-assembly, between phase separation and gel vitrification, called tactoid annealing, helps explain the discrepancies in order for chiral nematic CNC films dried at varying evaporation times.
Abstract: The self-assembly process in cellulose nanocrystal (CNC) film formation was studied as a function of evaporation time. It is known that the total evaporation time of CNC dispersions affects the structure of the film obtained, but the extension of different phases of the evaporation has not been explored. By extending the evaporation time of CNC suspensions after the onset of liquid crystallinity, the homogeneity of the resulting films could be improved as observed by polarized optical microscopy and scanning electron microscopy. Here, we show that an intermediate stage of self-assembly, between phase separation and gel vitrification, called tactoid annealing, helps explain the discrepancies in order for chiral nematic CNC films dried at varying evaporation times. This intermediate stage of self-assembly may be useful for designing highly ordered and homogenous CNC-based materials.

Journal ArticleDOI
TL;DR: The main focus is on the use of this framework in the systematic study of predominantly 2D tissue architectures and dynamics in vitro and how the nematic state is important in tissue behavior, such as epithelial expansion, tissue homeostasis, and the atherosclerosis disease state.
Abstract: Live tissues can self-organize and be described as active materials composed of cells that generate active stresses through continuous injection of energy. In vitro reconstituted molecular networks, as well as single-cell cytoskeletons show that their filamentous structures can portray nematic liquid crystalline properties and can promote nonequilibrium processes induced by active processes at the microscale. The appearance of collective patterns, the formation of topological singularities, and spontaneous phase transition within the cell cytoskeleton are emergent properties that drive cellular functions. More integrated systems such as tissues have cells that can be seen as coarse-grained active nematic particles and their interaction can dictate many important tissue processes such as epithelial cell extrusion and migration as observed in vitro and in vivo. Here, a brief introduction to the concept of active nematics is provided, and the main focus is on the use of this framework in the systematic study of predominantly 2D tissue architectures and dynamics in vitro. In addition how the nematic state is important in tissue behavior, such as epithelial expansion, tissue homeostasis, and the atherosclerosis disease state, is discussed. Finally, how the nematic organization of cells can be controlled in vitro for tissue engineering purposes is briefly discussed.

Journal ArticleDOI
TL;DR: A highly efficient photo-cross-linking chemistry, based on two-step oxygen-mediated thiol-acrylate click reactions, allows for nearly instant gelation of the main-chain LCE network upon exposure to UV light.
Abstract: Liquid crystal elastomers (LCEs) with intrinsic anisotropic strains are reversible shape-memory polymers of interest in sensor, actuator, and soft robotics applications. Rapid gelation of LCEs is required to fix molecular ordering within the elastomer network, which is essential for directed shape transformation. A highly efficient photo-cross-linking chemistry, based on two-step oxygen-mediated thiol-acrylate click reactions, allows for nearly instant gelation of the main-chain LCE network upon exposure to UV light. Molecular orientation from the pre-aligned liquid crystal oligomers can be faithfully transferred to the LCE films, allowing for preprogrammed shape morphing from two to three dimensions by origami- (folding-only) and kirigami-like (folding with cutting) mechanisms. The new LCE chemistry also enables widely tunable physical properties, including nematic-to- isotropic phase-transition temperatures (TN-I ), glassy transition temperatures (Tg ), and mechanical strains, without disrupting the LC ordering.

Journal ArticleDOI
Xiaojing Li1, Qian Li1, Yuxiang Wang1, Yiwu Quan1, Dongzhong Chen1, Yixiang Cheng1 
TL;DR: This paper designs a kind of aggregation-induced emission (AIE) chiral fluorescence emitters (R/S-BINOL-CN enantiomers) in the aggregate state that can self-assemble as the regularly planar Grandjean texture leading to high luminescence dissymmetry factor (glum).
Abstract: In this paper we designed a kind of aggregation-induced emission (AIE) chiral fluorescence emitters (R/S-BINOL-CN enantiomers) in the aggregate state. Chiral emissive nematic liquid crystals (N*-LCs) prepared by doping this kind of AIE-active R/S-BINOL-CN enantiomers into a common achiral nematic liquid crystal (N-LC, E7) can self-assemble as the regularly planar Grandjean texture leading to high luminescence dissymmetry factor (glum ) of aggregation-induced circularly polarized luminescence (AI-CPL) signal up to 0.41, which can be attributed to dipolar interactions from polar cyano groups and π-π interactions between binaphthyl moiety of the dopant R/S-BINOL-CN and biphenyl group of the host molecules (E7).

Journal ArticleDOI
03 Jul 2018
TL;DR: In this paper, the authors re-examine a classic question in liquid-crystal physics: What are the elastic modes of a nematic liquid crystal? The analysis uses a recent mathematical construction, which br...
Abstract: This article re-examines a classic question in liquid-crystal physics: What are the elastic modes of a nematic liquid crystal? The analysis uses a recent mathematical construction, which br...

Journal ArticleDOI
TL;DR: In this article, the phase behavior of suspensions of cellulose nanocrystals (CNCs) fractionated according to length is established, and it is shown that an increased aspect ratio can strongly favor liquid crystallinity without necessarily influencing gelation.
Abstract: Colloids of electrically charged nanorods can spontaneously develop a fluid yet ordered liquid crystal phase, but this ordering competes with a tendency to form a gel of percolating rods. The threshold for ordering is reduced by increasing the rod aspect ratio, but the percolation threshold is also reduced with this change; hence, prediction of the outcome is nontrivial. Here, we show that by establishing the phase behavior of suspensions of cellulose nanocrystals (CNCs) fractionated according to length, an increased aspect ratio can strongly favor liquid crystallinity without necessarily influencing gelation. Gelation is instead triggered by increasing the counterion concentration until the CNCs lose colloidal stability, triggering linear aggregation, which promotes percolation regardless of the original rod aspect ratio. Our results shine new light on the competition between liquid crystal formation and gelation in nanoparticle suspensions and provide a path for enhanced control of CNC self-organization for applications in photonic crystal paper or advanced composites.

Journal ArticleDOI
TL;DR: The design and functions of liquid-crystalline polymers with classifying them into conventional-, supramolecular-, dendritic-and network-type polymers are described in this paper.
Abstract: The design and functions of liquid-crystalline (LC) polymers with classifying them into conventional-, supramolecular-, dendritic- and network-type LC polymers are described. LC polymers show new functions as new devices in the field of energy and environment by incorporating mesogenic moieties exhibiting photonic, electronic and ionic functions. Supramolecular LC polymers show dynamic and unique properties because the mesogenic moieties are built with non-covalent interactions. Dendritic-type LC polymers exhibit liquid crystallinity by nanosegregation of aromatic and aliphatic moieties. Dendritic fork-like mesogens have also been prepared. A variety of nonmesogeic functional building blocks including fullerene, π-conjugated moieties, catenane, rotaxane and others can be incorporated into LC phases by attaching these dendritic moieties. LC networks are constructed in situ polymerization of polymerizable nematic or nanostructured liquid crystals. The specific characteristics of the LC networks have generated new research trends to develop well-defined polymers that exhibit optical, transport and separation properties. In these materials, through suitable design of LC monomers, the preservation of smectic, columnar and bicontinuous cubic phases has been successfully used for the development of membranes with one-dimensional, two-dimensional and three-dimensional nanostructures. The design and functions of various liquid-crystalline (LC) polymers including main-chain, side-chain and network LC polymers as well as dendritic structures are described. These polymeric LC materials can be applied for electro-, ion-, photo-active materials as well as mechanically tough materials. The introduction of supramolecular design has also generated a new category of functional LC materials.