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1.
Tetiana Orlova Rmi Plamont Alexis Depauw Nathalie Katsonis 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(39)
Nanoparticles tend to aggregate once integrated into soft matter and consequently, self‐assembling nanoparticles into large‐scale, regular, well‐defined, and ultimately chiral patterns remains an ongoing challenge toward the design and realization of organized superstructures of nanoparticles. The patterns of nanoparticles that are reported in liquid crystals so far are all static, and this lack of responsiveness extends to assemblies of nanoparticles formed in topological singularities and other localized structures of anisotropic matter. Here, it is shown that gold nanoparticles form spiral superstructures in polygonal fields of cholesteric liquid crystals. Moreover, when the cholesteric liquid crystals incorporate molecular photoswitches in their composition, the pitch of the nanoparticulate spirals follows the light‐induced reorganization of the cholesteric liquid crystals. These experimental findings indicate that chiral liquid crystals can be used as chiral and dynamic templates for soft photonic nanomaterials. Controlling the geometry of these spirals of nanoparticles will ultimately allow modulating the plasmonic signature of hybrid and chiral systems. 相似文献
2.
Hao Wang Hari Krishna Bisoyi Michael E. McConney Augustine M. Urbas Timothy J. Bunning Quan Li 《Advanced materials (Deerfield Beach, Fla.)》2019,31(39)
Light‐induced phenomena occurring in nature and in synthetic materials are fascinating and have been exploited for technological applications. Here visible‐light‐induced formation of a helical superstructure is reported, i.e., a cholesteric liquid crystal phase, in orientationally ordered fluids, i.e., nematic liquid crystals, enabled by a visible‐light‐driven chiral molecular switch. The cyclic‐azobenzene‐based chiral molecular switch exhibits reversible photoisomerization in response to visible light of different wavelengths due to the band separation of n–π* transitions of its trans‐ and cis‐isomers. Green light (530 nm) drives the trans‐to‐cis photoisomerization whereas the cis‐to‐trans isomerization process of the chiral molecular switch can be caused by blue light (440 nm). It is observed that the helical twisting power of this chiral molecular switch increases upon irradiation with green light, which enables reversible induction of helical superstructure in nematic liquid crystals containing a very small quantity of the molecular switch. The occurrence of the light‐induced helical superstructure enables the formation of diffraction gratings in cholesteric films. 相似文献
3.
Our research studied the bistable mechanism in electro-thermal switching reverse polymer-stabilized cholesteric texture (ET-RPSCT) light shutters. The bistable mechanism in ET-RPSCT is a result of a polymer distortion effect induced by applying a high-voltage pulse. It was found that long-pitch cholesteric liquid crystals will maintain a focal conic texture by a distorted polymer network which exhibits a translucent state. An annealing treatment method was used to recover cholesteric liquid crystals back to the planar texture through alignment layers. We compared the ET-RPSCT cells in different polymer network structures, which were built from different UV curable diacrylate monomers and concentrations, resulting in different anchoring forces and polymer distortion effects. We found that when the polymer network structure is tight and fiber-like, the long-pitch cholesteric liquid crystals are more stable in the focal conic texture because of polymer distortion, and are resistant to switching states. On the other hand, the long-pitch cholesteric liquid crystals recover to the planar texture easily by thermal switching due to a loose and grain-like polymer network structure. Furthermore, the effects of polymer structure on the electro-optical performance of ET-RPSCT were also investigated. 相似文献
4.
N. Tamaoki 《Advanced materials (Deerfield Beach, Fla.)》2001,13(15):1135-1147
Fixation of the molecular ordering of cholesteric liquid crystals is essential for use of these materials in color information technology. Methods to achieve this as well as thermal and photochemical control of the cholesteric pitch of the liquid crystals are addressed and applications in rewritable color recording are highlighted. The Figure shows a sample recorded using a laser. 相似文献
5.
6.
Based on the available data on the kinetics ofC-to-A nitrogen aggregation, theA-defect profile is calculated for a particular growth sector in diamond crystals grown by the temperature-gradient method.
The effects of the growth duration and temperature on the contents ofC andA nitrogen are examined. The formation ofA defects from single substitutional nitrogen is shown to occur even under typical growth conditions, at temperatures of 1300-1500°C,
and to have a significant effect on the structural perfection of diamond. 相似文献
7.
Cholesteric Liquid Crystal Shells as Enabling Material for Information‐Rich Design and Architecture
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Mathew Schwartz Gabriele Lenzini Yong Geng Peter B. Rønne Peter Y. A. Ryan Jan P. F. Lagerwall 《Advanced materials (Deerfield Beach, Fla.)》2018,30(30)
The responsive and dynamic character of liquid crystals (LCs), arising from their ability to self‐organize into long‐range ordered structures while maintaining fluidity, has given them a role as key enabling materials in the information technology that surrounds us today. Ongoing research hints at future LC‐based technologies of entirely different types, for instance by taking advantage of the peculiar behavior of cholesteric liquid crystals (CLCs) subject to curvature. Spherical shells of CLC reflect light omnidirectionally with specific polarization and wavelength, tunable from the UV to the infrared (IR) range, with complex patterns arising when many of them are brought together. Here, these properties are analyzed and explained, and future application opportunities from an interdisciplinary standpoint are discussed. By incorporating arrangements of CLC shells in smart facades or vehicle coatings, or in objects of high value subject to counterfeiting, game‐changing future uses might arise in fields spanning information security, design, and architecture. The focus here is on the challenges of a digitized and information‐rich future society where humans increasingly rely on technology and share their space with autonomous vehicles, drones, and robots. 相似文献
8.
Juntao Li Hari Krishna Bisoyi Jiajun Tian Jinbao Guo Quan Li 《Advanced materials (Deerfield Beach, Fla.)》2019,31(10)
Functional soft materials exhibiting distinct functionalities in response to a specific stimulus are highly desirable towards the fabrication of advanced devices with superior dynamic performances. Herein, two novel light‐driven chiral fluorescent molecular switches have been designed and synthesized that are able to exhibit unprecedented reversible Z/E photoisomerization behavior along with tunable fluorescence intensity in both isotropic and anisotropic media. Cholesteric liquid crystals fabricated using these new fluorescent molecular switches as chiral dopants exhibit reversible reflection color tuning spanning the visible and infrared region of the spectrum. Transparent display devices have been fabricated using both low chirality and high chirality cholesteric films that operate either exclusively in fluorescent mode or in both fluorescent and reflection mode, respectively. The dual mode display device employing short pitch cholesteric film is able to function on demand under all ambient light conditions including daylight and darkness with fast response and high resolution. Moreover, the proof‐of‐concept for a “remote‐writing board” using cholesteric films containing one of the light‐driven chiral fluorescent molecular switches with ease of fabrication and operation is disclosed herein. Such optically rewritable transparent display devices enabled by light‐driven chiral fluorescent molecular switches pave a new way for developing novel display technology under different lighting conditions. 相似文献
9.
Polymer‐Stabilized Micropixelated Liquid Crystals with Tunable Optical Properties Fabricated by Double Templating
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Yuji Sasaki Motoshi Ueda Khoa V. Le Reo Amano Shin Sakane Shuji Fujii Fumito Araoka Hiroshi Orihara 《Advanced materials (Deerfield Beach, Fla.)》2017,29(37)
Self‐organized nano‐ and microstructures of soft materials are attracting considerable attention because most of them are stimuli‐responsive due to their soft nature. In this regard, topological defects in liquid crystals (LCs) are promising not only for self‐assembling colloids and molecules but also for electro‐optical applications such as optical vortex generation. However, there are currently few bottom‐up methods for patterning a large number of defects periodically over a large area. It would be highly desirable to develop more effective techniques for high‐throughput and low‐cost fabrication. Here, a micropixelated LC structure consisting of a square array of topological defects is stabilized by photopolymerization. A polymer network is formed on the structure of a self‐organized template of a nematic liquid crystal (NLC), and this in turn imprints other nonpolymerizable NLC molecules, which maintains their responses to electric field and temperature. Photocuring of specific local regions is used to create a designable template for the reproducible self‐organization of defects. Moreover, a highly diluted polymer network (≈0.1 wt% monomer) exhibits instant on–off switching of the patterns. Beyond the mere stabilization of patterns, these results demonstrate that the incorporation of self‐organized NLC patterns offers some unique and unconventional applications for anisotropic polymer networks. 相似文献
10.
纤维素及其衍生物的胆甾型液晶结构 总被引:3,自引:0,他引:3
综术了纤维毒素衍生物胆甾型溶致液晶结构的纤维素衍生物的复合物的结构研究的进展。纤维素衍生物能在多种溶剂中形成胆甾型溶致液晶,其液晶相具有多重织构特性,即它的多种织构的存在与外界条件如溶液的浓度、温度等有很大关系。在纤维素衍生物的胆甾型液晶溶液中还可观察到多种向错结构,含纤维素衍生物的高分子复合物的合成一方面使纤维素衍生物胆甾型液晶结构的研究进入了更微观的层次,另一方面其本身就具有潜在的应用前景。 相似文献
11.
Abstract This paper deals with the enmicrocapsulation of cholesteric liquid crystals by the colloid coaversation process. This incident light reflection study reveals that the encapsulated liquid crystal films sustain highly sensitive and precise temperature gradients with responding abilities determined by their iridescent coloration. 相似文献
12.
《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1986,248(1):20-28
The up-to-date state of investigations of charged particle coherent radiation in liquid crystals is presented with most attention being paid to coherent radiation in chiral liquid crystals. A detailed analysis of Cherenkov radiation and “structure Cherenkov” radiation in cholesteric liquid crystals is given. It is shown that there are essential differences in the characteristics of Cherenkov radiation in cholesterics compared to Cherenkov radiation in homogeneous media. These reveal themselves in the spectral and angular distributions of the radiation and in its polarization properties. Many of these, in particular the two cones of emission, the divergence of the differential with respect to frequency (or angle) of the emission intensity and the shift of the threshold velocity for Cherenkov radiation, are common to Cherenkov radiation in any periodic medium. The prospects for experimental observation of the examined Cherenkov radiation peculiarities in chiral liquid crystals are briefly discussed, and the significance of the relevant measurements for studying coherent radiation from charged particles in other periodic media and other frequency ranges are noted. 相似文献
13.
Shinichi Suto Takao Iwaya Yutaka Ohno Mikio Karasawa 《Journal of Materials Science》1991,26(11):3073-3080
Ethyl cellulose (EC) and hydroxypropyl cellulose (HPC) films were cast under different conditions and were observed optically. The creep behaviour of those films was determinedin vacuo as a function of applied stress or temperature and was analysed on the basis of the Eyring thermally activated process.EC and HPC films cast from liquid crystal-forming systems remained cholesteric liquid crystalline order (the cholesteric sense was different in each case), whereas EC film cast from non-liquid crystal system (benzene) had no liquid crystalline order and was amorphous. The Eyring activated process could be applied to the creep behaviour of our films and activated parameters could be evaluated. The activated volumeV was of the order of 1 nm3 and greatly depended on the casting conditions and testing temperature. The value ofV tended to decrease as the liquid crystalline order increased. The value ofV was smaller than the size of liquid crystalline domain. 相似文献
14.
Jianguo Zhao Utku Gulan Takafumi Horie Naoto Ohmura Jun Han Chao Yang Jie Kong Steven Wang Ben Bin Xu 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(18)
Biological liquid crystals, a rich set of soft materials with rod‐like structures widely existing in nature, possess typical lyotropic liquid crystalline phase properties both in vitro (e.g., cellulose, peptides, and protein assemblies) and in vivo (e.g., cellular lipid membrane, packed DNA in bacteria, and aligned fibroblasts). Given the ability to undergo phase transition in response to various stimuli, numerous practices are exercised to spatially arrange biological liquid crystals. Here, a fundamental understanding of interactions between rod‐shaped biological building blocks and their orientational ordering across multiple length scales is addressed. Discussions are made with regard to the dependence of physical properties of nonmotile objects on the first‐order phase transition and the coexistence of multi‐phases in passive liquid crystalline systems. This work also focuses on how the applied physical stimuli drives the reorganization of constituent passive particles for a new steady‐state alignment. A number of recent progresses in the dynamics behaviors of active liquid crystals are presented, and particular attention is given to those self‐propelled animate elements, like the formation of motile topological defects, active turbulence, correlation of orientational ordering, and cellular functions. Finally, future implications and potential applications of the biological liquid crystalline materials are discussed. 相似文献
15.
The ability to tune molecular self‐organization with an external stimulus is a main driving force in the bottom‐up nanofabrication of molecular devices. Light‐driven chiral molecular switches or motors in liquid crystals that are capable of self‐organizing into optically tunable helical superstructures undoubtedly represent a striking example, owing to their unique property of selective light reflection and which may lead to applications in the future. In this review, we focus on different classes of light‐driven chiral molecular switches or motors in liquid crystal media for the induction and manipulation of photoresponsive cholesteric liquid crystal systems and their consequent applications. Moreover, the change of helical twisting powers of chiral dopants and their capability of helix inversion in the induced cholesteric phases are highlighted and discussed in the light of their molecular geometric changes. 相似文献
16.
Alexander Ryabchun Federico Lancia Jiawen Chen Dmitry Morozov Ben L. Feringa Nathalie Katsonis 《Advanced materials (Deerfield Beach, Fla.)》2020,32(47):2004420
Unravelling the rules of molecular motion is a contemporary challenge that promises to support the development of responsive materials and is likely to enhance the understanding of functional motion. Advances in integrating light-driven molecular motors in soft matter have led to the design and realization of chiral nematic (cholesteric) liquid crystals that can respond to light with modification of their helical pitch, and also with helix inversion. Under illumination, these chiral liquid crystals convert from one helical geometry to another. Here, a series of light-driven molecular motors that feature a rich configurational landscape is presented, specifically which involves three stable chiral states. The succession of chiral structures involved in the motor cycle is transmitted at higher structural levels, as the cholesteric liquid crystals that are formed can interconvert between helices of opposite handedness, reversibly. In these materials, the dynamic features of the motors are thus expressed at the near-macroscopic, functional level, into addressable colors that can be used in advanced materials for tunable optics and photonics. 相似文献
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18.
Gia Petriashvili Guram Chilaya Mario Ariosto Matranga Maria Penelope De Santo Gaetano Cozza Riccardo Barberi Jesus del Barrio Luiz Silvino Chinelatto Jr. Luis Oriol Milagros Piol 《Optical Materials》2009,31(11):1693-1696
We present the synthesis and characterization of fluorene based materials for mirror less laser applications. Mirror less lasing is obtained from a cholesteric liquid crystals mixture, that acts as a resonator, doped with a photoluminescent dye, that acts as an active medium. We propose to use fluorene based compounds to combine two necessary properties to achieve laser emission: chirality and luminescence. Two different compounds, a trimer and an oligomer are synthesized. The trimer and the oligomer are both prepared with chiral moieties and, in addition, they are liquid crystalline compatible. More, oligofluorenes are good blue emitters and the emission quantum yield is around 0.8 in the violet–blue range. These fluorene based compounds are used in cholesteric liquid crystals mixtures as luminescent chiral dopants and a fine tuning of the laser emission is obtained. The dependence of lasing efficiency on concentration and the handedness of chiral luminescent dopants are investigated. 相似文献
19.
Upindranath Singh Fredrick Davis Saeed Mohan Geoffrey Mitchell 《Journal of Materials Science》2013,48(21):7613-7619
Electrospinning was used to generate polymer nanofibres from blends of poly-vinyl cinnamate (PVCN) and a cholesteric silicone polymer. Only blends that contained at least 40 % of PVCN produced fibres. Both differential scanning calorimetry and electron dispersion spectroscopy data indicate that the samples are miscible over a wide temperature interval. The variation of fibre diameter with concentration is nonlinear with a well-defined minimum corresponding to an 80 % PVCN blend. The fibres are birefringent with Kerr constants similar to that of cholesteric liquid crystals. Although not significant, the Kerr constant increases with increasing silicone polymer concentration. 相似文献
20.
G S Ranganath 《Bulletin of Materials Science》1983,5(3-4):333-342
The hydrodynamical behaviour of cholesteric liquid crystals has been considered in the limit of low amplitude and low frequency distortions and motions. It is shown that there are interesting analogies with superfluid-hydrodynamics, such as the fountain effect, thermal superconductivity and temperature wave propagation. In certain situations, there is an unusual formation of a boundary layer at low velocities, and in certain others the properties resemble those of percolation in porous media. Results concerning some special phenomena peculiar to cholesteric liquid crystals are also presented. Finally it is pointed out that there should be two types of second sound in chiral smectic C. 相似文献