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1.
J. Lub W.&#x;P.&#x;M. Nijssen R.&#x;T. Wegh J.&#x;P.&#x;A. Vogels A. Ferrer 《Advanced functional materials》2005,15(12):1961-1972
This paper describes the synthesis of photoisomerizable derivatives of isosorbide. These derivatives contain a stilbene or cinnamate moiety and can therefore be used as photoisomerizable chiral compounds in cholesteric liquid‐crystalline mixtures. The reflection wavelength of cholesteric layers made from these mixtures is increased by UV irradiation due to the fact that the Z‐isomers of these derivatives exhibit a lower helical twisting power than the corresponding E‐isomers. The cinnamate derivatives are very suitable for use in cholesteric color filters that find application in liquid‐crystal displays. 相似文献
2.
A new liquid‐crystal composite, composed of photopolymerizable self‐assembled fibers and a smectic liquid crystal, and its photopolymerized composite have been prepared. The fibers oriented along the smectic layers are obtained by self‐assembly of an amino acid derivative with terminal methacryloyl groups in the smectic liquid crystal. The oriented fibrous structures are fixed by photopolymerization, resulting in the formation of microgrooves on the substrate surfaces. The aligned direction of the liquid‐crystalline molecules is changed to the direction along the fibers after thermal annealing. The patterning of liquid‐crystal alignment is achieved for these liquid‐crystal composites by patterned photopolymerization. 相似文献
3.
J.J. Ge S.‐C. Hong B.Y. Tang C.Y. Li D. Zhang F. Bai B. Mansdorf F.W. Harris D. Yang Y.‐R. Shen S.Z.D. Cheng 《Advanced functional materials》2003,13(9):718-725
Ultraviolet (UV) polymerizable discotic liquid‐crystalline (DLC) molecules (2,3,6,7,10,11‐hexakis(4′‐acryloy‐m‐alkyloxybenzoyoxy)triphenylene [HAHBT‐m, where m was the number of methylene units, and here m = 6 (HAHBT‐6)]) were assembled to form a negative retardation film with an oblique optical axis on a specifically designed rubbing‐aligned polyimide layer surface [6FDA‐11CBBP (where 11 is the number of methylene units in the side chains)]. The side chains of this polyimide were terminated by cyanobiphenyl groups. Surface‐enhanced Raman scattering (SERS) and optical second harmonic generation results showed that rubbing caused a surface structural re‐arrangement in the alignment layer resulting in a negative pre‐tilt angle (θs) of –8.5° (which was in the direction opposite to the rubbing direction). The molecular topology at the rubbed surface was governed by a stable fold‐like bent structure of the cyanobiphenyl side chains, in which the CN groups preferentially pointed down towards the surface. When the DLC molecules were deposited onto the alignment surface and polymerized via UV irradiation to generate a new optical film, an oblique optical axis with an average tilt angle of –18.6° with respect to the film normal was detected using ellipsometric measurements. This tilted optical axis was developed by the DLC molecules being wedged on top of the cyanobiphenyl groups when in the bent conformation. Furthermore, the tilt angle difference between the θs at the alignment surface and at the air interface of the DLC molecules was attributed to a splay deformation of the DLC molecules along the film surface normal. Optical modeling has also confirmed our experimental observations. 相似文献
4.
本文介绍了电子显示器的发展,液晶显示器(LCD)、简单矩阵LCD和有源矩阵LCD的现状,以及LCD的发展趋势与展望。 相似文献
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Understanding the complex interplay between the 3D structural hierarchy within thin films of conjugated polymers and the properties of devices based thereon is starting to be recognized as an important challenge in the continued development of these materials for a range of applications. As a result, for example, accurate measurements of molecular orientation and elucidation of its influence on optical characteristics are of significant interest. Here we report an improved optical method to determine both the order parameter and the angle between the polymer backbone director and the optical transition dipole moment for the lowest energy π–π* absorption peak in uniaxially aligned thin films of conjugated polymers. The method uses a combination of polarized Raman spectroscopy and UV‐vis spectroscopy and is based on a general theoretical treatment to describe the expected Raman and optical absorption anisotropies of such films. It is applied to study the orientation within thermotropically aligned films of the electroluminescent fluorene‐based copolymer poly(9,9‐dioctylfluorene‐co‐bithiophene) (F8T2). A more highly axial transition dipole moment is found for the dominant long wavelength absorption peak of F8T2 compared to that of other fluorene‐based (co)polymers. The angle between the polymer backbone director and the transition dipole is estimated to be β ≤ 3°, a deduction that helps to explain the relatively large optical dichroism for aligned films of F8T2 and that offers the prospect of highly polarized electroluminescence from F8T2‐based light‐emitting diodes. 相似文献
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A. Trajkovska‐Petkoska R. Varshneya T.&#x;Z. Kosc K.&#x;L. Marshall S.&#x;D. Jacobs 《Advanced functional materials》2005,15(2):217-222
Polymer cholesteric liquid‐crystal (PCLC) flakes were investigated for their electro‐optical behavior under an applied alternating‐current field. Shaped flakes, fabricated using soft lithography and suspended in dielectric‐fluid‐filled cells, reoriented more uniformly than randomly shaped flakes made by fracturing of PCLC films. Extensive characterization found shaped flakes to be smooth and uniform in size, shape, and thickness. Reorientation in applied fields as low as tens of mVrms μm–1 was fastest for flakes with lateral aspect ratios greater than 1:1, confirming theoretical predictions based on Maxwell–Wagner polarization. Brilliant reflective colors and inherent polarization make shaped PCLC flakes of interest for particle displays. 相似文献
9.
A. Trajkovska‐Petkoska R. Varshneya T.&#x;Z. Kosc K.&#x;L. Marshall S.&#x;D. Jacobs 《Advanced functional materials》2005,15(2)
The cover shows a variety of shaped flakes fabricated from polymer cholesteric liquid‐crystal material using soft lithography. In work reported by Jacobs and co‐workers on p. 217, the micrometer‐sized flakes exhibit brilliant circularly polarized selective reflection colors without polarizers or color filters when placed in a fluid‐filled electro‐optic cell. With the application of a low‐magnitude alternating current field, the flakes reorient in hundreds of milliseconds and the colors disappear. Polymer cholesteric liquid‐crystal (PCLC) flakes were investigated for their electro‐optical behavior under an applied alternating‐current field. Shaped flakes, fabricated using soft lithography and suspended in dielectric‐fluid‐filled cells, reoriented more uniformly than randomly shaped flakes made by fracturing of PCLC films. Extensive characterization found shaped flakes to be smooth and uniform in size, shape, and thickness. Reorientation in applied fields as low as tens of mVrms μm–1 was fastest for flakes with lateral aspect ratios greater than 1:1, confirming theoretical predictions based on Maxwell–Wagner polarization. Brilliant reflective colors and inherent polarization make shaped PCLC flakes of interest for particle displays. 相似文献
10.
Fast and high‐contrast responses with low driving voltages in twisted nematic (TN) cells are achieved for anisotropically oriented structures of liquid‐crystalline physical gels. They are prepared by hydrogen‐bonded aggregation of an L ‐lysine‐based gelator in nematic liquid crystals. When the mixtures of the nematic liquid crystals and the gelator are prepared in TN cells, fibrous aggregates of the gelator align along the twisted‐nematic orientation of the liquid crystal, forming oriented phase‐separated structures. 相似文献
11.
M.&#x;H. Song B. Park S. Nishimura T. Toyooka I.&#x;J. Chung Y. Takanishi K. Ishikawa H. Takezoe 《Advanced functional materials》2006,16(14):1793-1798
A liquid crystal (LC) photonic device with an anisotropic optical heterojunction structure has been fabricated. The device has a phase‐retarding nematic LC (NLC) layer sandwiched between two polymer cholesteric LC films with right‐handed helices of different pitches. Electrotunable non‐reciprocal light transmittance and unidirectional circularly polarized (CP) lasing emission have been successfully demonstrated for this device structure. Two left CP (LCP) lasing emission peaks are observed at the edges of the overlapping region between the two photonic bands in the structure and are shifted upon the application of a voltage. In contrast, a non‐reciprocal right CP (RCP) lasing emission peak emerges at one of the band edges and diminishes upon the application of a voltage. These phenomena are interpreted based on the selective reflection of RCP light and the reorientation of the NLC molecules by the application of a voltage. 相似文献
12.
The fabrication of a one‐dimensional photonic crystal without time‐reversal and space‐inversion symmetries was pursued. Theoretical studies predict that such a system would exhibit unusual optical properties, including indirect photonic bandgaps and backward wave propagating eigenmodes. Such a system can be created experimentally by combing magnetooptical nanoparticles with a chiral nematic liquid crystal. The manner in which nanoparticles co‐assemble with a chiral nematic liquid crystal was investigated. It was determined that the addition of nanoparticles to a 5CB‐COC system disrupts the system's helical structure. This disruption lowers the system's phase transition temperatures and inhibits the system's ability to form reflectivity peaks. 相似文献
13.
Jonathan P. Bramble Daniel J. Tate Derek J. Revill Khizar H. Sheikh James R. Henderson Feng Liu Xiangbing Zeng Goran Ungar Richard J. Bushby Stephen D. Evans 《Advanced functional materials》2010,20(6):914-920
A novel method of creating planar aligned columnar discotic liquid crystals (cDLCs) on surfaces, which also gives control over the azimuthal angle, is presented. Surfaces are chemically patterned with stripes via microcontact printing of organothiol self‐assembled monolayers (SAMs) on gold, or via deep UV patterning of organosilane SAMs on silicon. These are then used to isolate long droplets of cDLCs by dewetting in the isotropic phase. Upon cooling from the isotropic into the hexagonal columnar phase, polarizing microscopy reveals that the cDLC aligns in a planar orientation. Results for three triphenylene derivatives (HAT‐6, HHTT, H7T) and for a phthalocyanine derivative (8H2Pc) are presented. H7T and HAT‐6 are found to align with the director perpendicular to the stripe direction, but HHTT and 8H2Pc align parallel to the stripe direction. This relatively simple new method for creating planar aligned columnar phases of DLCs gives control over the azimuthal angle: a condition required for organic field‐effect transistor applications of cDLCs. 相似文献
14.
H. Monobe K. Kiyohara N. Terasawa M. Heya K. Awazu Y. Shimizu 《Advanced functional materials》2003,13(12):919-924
The infrared photoinduced alignment change of liquid‐crystal domains was investigated for a hexagonal columnar mesophase of a liquid‐crystalline triphenylene derivative. A uniform and anisotropic alignment change of domains was observed when a polarized infrared (IR) light corresponding to the wavelength of the aromatic C–C stretching absorption band of the triphenylene core was used to irradiate the sample. The relationship between the aligned azimuthal angle of the columnar axis and the polarization of the IR incident irradiation was investigated. IR absorption dichroism is induced as a result of the reorientation of triphenylene core. Texture observation and polarizing microscope FTIR spectra show that a change of the molecular alignment occurred and that the direction of columns depends on the polarization angle of the IR light used for irradiation. The mechanism of the alignment change in a columnar liquid crystal film by IR irradiation is also discussed. The technique could provide a novel technology to control the columnar alignment of highly viscous liquid crystals. 相似文献
15.
S. T. Lagerwall A. Dahlgren P. Jgemalm P. Rudquist K. D&#x;hav H. Pauwels R. Dabrowski W. Drzewinski 《Advanced functional materials》2001,11(2):87-94
Antiferroelectric order has been known to exist in liquid crystals since more than a decade and is now an intensely studied field of research. The great application potential of antiferroelectric liquid crystals has especially been demonstrated in sophisticated flat‐panel display prototypes, which nevertheless have not yet reached manufacturing, due to the severe intrinsic problem of folds in the smectic layers, which drastically limit the achievable contrast, and which seem impossible to circumvent. By proper molecular design, we have developed and tested a new generic class of antiferroelectric materials that present an elegant solution to this problem. Their optical properties make them unique not only among liquid crystals but among electro‐optical materials in general. The design of this generic class, which we call orthoconic, also gives an illustrative example of the physical meaning of the addition of tensorial properties. Normal surface‐stabilized antiferroelectrics are optically positive biaxial crystals, with an effective optic axis along the smectic layer normal. The surprising optical property of the corresponding orthoconic antiferroelectric can be formulated as a theorem: When the tilt directions in adjacent smectic layers are made perpendicular to each other, the material becomes negatively uniaxial with the optic axis lying perpendicular to the smectic layer normal. The electro‐optic effect in such a material is based on the fact that the optic axis can be switched between three mutually orthogonal directions, corresponding to zero, negative, or positive values of the applied electric field. 相似文献
16.
S. Abraham S. Paul G. Narayan S.&#x;K. Prasad D.&#x;S.&#x;S. Rao N. Jayaraman S. Das 《Advanced functional materials》2005,15(10)
A chiral liquid‐crystalline phase is reported for the first time in sugar‐based mesogens containing free hydroxyl groups by Jayaraman, Das, and co‐workers. Earlier reports have shown that hydrogen‐bonding networks between hydroxyl groups in mesogenic sugars usually result in the manifestation of achiral smectic and columnar phases. The results reported on p. 1579 indicate that the manifestation of smectic C* phases in sugar‐based bolaamphiphiles depends critically on the length of the methylene spacers and the presence of the azobenzene chromophore. Amphiphilic sugars exhibit both lyotropic and thermotropic liquid‐crystalline behavior. Interestingly, in spite of the abundance of chiral centers in amphiphilic sugars, their liquid‐crystalline phases do not exhibit macroscopic chirality. Herein, we report on the first observation of macroscopic chirality in sugar‐based bolaamphiphiles containing free hydroxyl groups. The manifestation of the chiral smectic C* phase in these bolaamphiphiles has been observed to be critically dependent on the presence of the azobenzene moiety and the suitable length of the methylene spacer. These results imply that by suitable selection of linker groups, mesogenic bolaamphiphiles possessing macroscopic chirality can be designed using a variety of naturally available sugar derivatives. 相似文献
17.
S. Abraham S. Paul G. Narayan S.&#x;K. Prasad D.&#x;S.&#x;S. Rao N. Jayaraman S. Das 《Advanced functional materials》2005,15(10):1579-1584
Amphiphilic sugars exhibit both lyotropic and thermotropic liquid‐crystalline behavior. Interestingly, in spite of the abundance of chiral centers in amphiphilic sugars, their liquid‐crystalline phases do not exhibit macroscopic chirality. Herein, we report on the first observation of macroscopic chirality in sugar‐based bolaamphiphiles containing free hydroxyl groups. The manifestation of the chiral smectic C* phase in these bolaamphiphiles has been observed to be critically dependent on the presence of the azobenzene moiety and the suitable length of the methylene spacer. These results imply that by suitable selection of linker groups, mesogenic bolaamphiphiles possessing macroscopic chirality can be designed using a variety of naturally available sugar derivatives. 相似文献
18.
F.&#x;P. Nicoletta G. Chidichimo D. Cupelli G. De&#x;Filpo M. De&#x;Benedittis B. Gabriele G. Salerno A. Fazio 《Advanced functional materials》2005,15(6):995-999
Polymer‐dispersed liquid crystals (PDLCs) are liquid‐crystal dispersions within a polymer matrix. These films can be changed from an opaque to a transparent state by applying a suitable alternating‐current electric field. PDLCs have attracted the interest of researchers for their applications as light shutters, smart windows, and active displays. For such applications, electrochromic devices, which change color as a result of electrochemical reactions, have also become a recent focus of research. Herein, we report our preliminary results on bifunctional devices based on PDLCs that host electrochromic guest molecules. Such devices allow both an independent and fast switching from a scattering opaque state to a transmissive transparent state owing to liquid‐crystal reorientation and a color change from white (pale yellow) to dark blue, due to either oxidation or reduction of the electrochromic molecules. 相似文献
19.
N.&#x;A. Lockwood J.&#x;C. Mohr L. Ji C.&#x;J. Murphy S.&#x;P. Palecek J.&#x;J. de&#x;Pablo N.&#x;L. Abbott 《Advanced functional materials》2006,16(5):618-624
We have investigated the culture of human embryonic stem cells (hESCs) on interfaces of the thermotropic liquid crystal, TL205, that are decorated with thin films of the extracellular matrix, Matrigel. hESCs seeded at the liquid‐crystal/Matrigel interface survive for weeks, and cell colonies grow over this time. The cells show levels of differentiation comparable to that observed for cells on Matrigel‐coated glass controls. Polarized and fluorescence microscopy reveal that the orientational order of the liquid crystal is coupled to the presence and organization of Matrigel. This enables straightforward imaging of the reorganization of Matrigel by the hESCs through changes in the appearance of the liquid crystal when observed using polarized light microscopy. The coupling between Matrigel and TL205 thus provides a simple tool for monitoring the reorganization of the Matrigel film over time. Our results suggest new approaches to the culture of cells and measurements of cell–extracellular‐matrix interactions. 相似文献
20.
N.&#x;A. Lockwood J.&#x;C. Mohr L. Ji C.&#x;J. Murphy S.&#x;P. Palecek J.&#x;J. de&#x;Pablo N.&#x;L. Abbott 《Advanced functional materials》2006,16(5)
New approaches to the culture of cells and measurements of cell–extracellular‐matrix interactions are suggested in the Full Paper by Abbott and co‐workers on p. 618. The culture of human embryonic stem cells (hESCs) on interfaces of a thermotropic liquid crystal that are decorated with thin films of the extracellular matrix, Matrigel, are investigated. The cover image shows the polarized light microscopy image of hESCs cultured for three days on a Matrigel‐coated film of liquid crystal hosted within a TEM grid. The hESCs reorganized the Matrigel, leading to patterned orientations of the liquid crystal. We have investigated the culture of human embryonic stem cells (hESCs) on interfaces of the thermotropic liquid crystal, TL205, that are decorated with thin films of the extracellular matrix, Matrigel. hESCs seeded at the liquid‐crystal/Matrigel interface survive for weeks, and cell colonies grow over this time. The cells show levels of differentiation comparable to that observed for cells on Matrigel‐coated glass controls. Polarized and fluorescence microscopy reveal that the orientational order of the liquid crystal is coupled to the presence and organization of Matrigel. This enables straightforward imaging of the reorganization of Matrigel by the hESCs through changes in the appearance of the liquid crystal when observed using polarized light microscopy. The coupling between Matrigel and TL205 thus provides a simple tool for monitoring the reorganization of the Matrigel film over time. Our results suggest new approaches to the culture of cells and measurements of cell–extracellular‐matrix interactions. 相似文献