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Martin Schadt 《Molecular Crystals and Liquid Crystals》2014,594(1):11-20
Prerequisite for virtually all nematic field-effects on which liquid crystal displays (LCDs) are based is stable, uniaxial surface alignment with defined bias tilt angle between the long liquid crystal (LC) axes and their display boundaries. Since the invention of the TN-LCD [1] in 1970 until recently this was achieved by confining liquid crystals between mechanically brushed surfaces [2–4]. We have first shown in the 1990s that, non-mechanical, uniaxial, tilted and patterned LC-alignment is possible by anisotropic Van der Waals surface interactions [5], namely by directional polymerization of photo-sensitive side-chain polymers films [5, 6] by linear polarized UV light. The LPP model is reviewed and its applications enabling high resolution multi-domain liquid crystal displays operated in transmission and reflection are discussed. Examples are given for optical retarders integrated into LCDs, anisotropic liquid crystal polymer (LCP)-films for 3D imaging, interference color filters, wide-view films and anisotropic polymer surface topologies. 相似文献
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Jinal Gajjar Rajesh H. Vekariya Vinay S. Sharma 《Molecular Crystals and Liquid Crystals》2018,668(1):48-58
A new class of supramolecular calix[4]resorcinarene substituted alkoxy side chain (-OC5H11, -OC8H17, -OC10H21) has been synthesized and well characterized. These supramolecular compounds were investigated by polarizing optical microscope (POM), differential scanning calorimetry (DSC), thermogravimmetric analysis (TGA) and high-temperature X-ray diffraction studies (XRD). The present synthesized supramolecular derivatives are promising to stabilize the hexagonal columnar phase over a broad thermal range. All the synthesized derivatives showed hexagonal columnar phase at lower temperature and showed enantiotropical nature. Compound 2a with small alkyl spacer on eight side showed higher thermal stability as compare to higher alkyl spacer substituted compounds 2b and compound 2c. These research results suggest that calix[4]resorcinarene was a good platform to construct bowl-shaped derivatives to exhibits the columnar liquid crystal phase and the observed liquid crystalline properties were greatly effected by the substituted alkoxy side chain on eight side of calix[4]resorcinarene skeletone. All the synthesized compounds were characterized by FT-IR, 1H NMR and 13C NMR spectroscopy. 相似文献
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Hyung Jong Kim Ik Rang Choe Tae Ryang Hong Ju Sik Kang Hyun Ah Um Min Ju Cho 《Molecular Crystals and Liquid Crystals》2015,621(1):31-39
A series of bipolar host materials containing dibenzo[b,d]thiophene (DBT) or dibenzo[b,d]thiophene 5,5-dioxide core were successfully synthesized, and their physical, photophysical, and electrochemical properties were investigated. The three host materials showed well-localized electron distribution at the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) states, as evidenced by theoretical calculations. Triplet energies of the new host materials are higher than 2.6 eV, and the blend film with bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) as a blue phosphorescent dopant showed highly efficient energy transfer between the host material and dopant. 相似文献
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New sodium iron orthophosphate NaFe 4 2+ Fe 3 3+ [PO4]6 was synthesized by the hydrothermal method. The crystal structure (sp. gr. $P\bar 1$ ) was established by the heavy-atom method, with the exact chemical formula of the compound being unknown; R hkl = 0.0492, R whkl = 0.0544, S = 0.52. The new compound is analogous to iron phosphate Fe 3 2+ Fe 4 3+ [PO4]6 studied earlier. However, these two compounds differ in the Fe2+ and Fe3+ contents, because Na+ ions in the new compound are located at the centers of symmetry not occupied earlier. 相似文献
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A combinatorial-topological analysis of the La3Ga[6]Ga 4 [4] Ge[4]O14 and La3Ge[6]Ge 2 [5] Ge 2 [4] Ga[4]O16 gallogermanates, which have MT and MPT microporous frameworks composed of M octahedra (GeO6, GaO6), T tetrahedra (GeO4, GaO4), and P pyramids (GeO5), is performed using the method of coordination sequences with the TOPOS 3.2 program package. It is established that the La3Ga[6]Ga 4 [4] Ge[4]O14 gallogermanate is characterized by a crystal-forming net 6 6 6 (of the graphite type). A new type of the binodal net 6 10 1 0 + 6 10 (2: 1) is revealed in the La3Ge[6]Ge 2 [5] Ge 2 [4] Ga[4]O16 gallogermanate. The cyclic cluster precursors composed of six polyhedra with a lanthanum template atom at the center of the LaMT 5 and LaMP 3 T 3 clusters are identified by the two-color decomposition of the nets in the structures of the La3Ga[6]Ga 4 [4] Ge[4]O14 and La3Ge[6]Ge 2 [5] Ge 2 [4] Ga[4]O16 gallogermanates. The coordination numbers of the cluster precursors in these structures are found to be equal to 6 and 4 for two-dimensional nets and 8 and 6 for three-dimensional nets, respectively. 相似文献
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I. V. Rozhdestvenskaya Yu. M. Bronzova O. V. Frank-Kamenetskaya A. A. Zolotarev L. G. Kuznetsova I. I. Bannova 《Crystallography Reports》2008,53(2):223-227
The crystal structure of a natural calcium-lithium-aluminum tourmaline, which has the unique composition (Ca0.62Na0.32□0.06)(Al1.08Li0.99Fe 0.66 2+ Mg0.24Ti0.03)Al6[Si6O18](BO3)3(OH2.28O0.72) · (F0.84O0.16), is refined (R = 0.019, R w = 0.022, S = 1.47). It is found that the O(1)(W) site is split into two sites, O(1) and O(11), which are incompletely occupied by fluorine and oxygen anions, respectively, and that the O(3)(V) site contains bivalent oxygen anions. The solid solution studied is close in composition to the liddicoatite mineral species and differs from the latter one by the Li: Al ratio in the Y octahedra and the presence of bivalent oxygen anions in the O(3) site. The tourmaline studied differs from the hypothetical oxyliddicoatite by the population of the O(1)(W) site by fluorine and accommodation of additional oxygen anions in the O(3)(V) site. 相似文献
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I. V. Rozhdestvenskaya T. V. Setkova O. S. Vereshchagin A. G. Shtukenberg Yu. B. Shapovalov 《Crystallography Reports》2012,57(1):57-63
The crystal structures of synthetic tourmalines with a unique composition containing 3d elements (Ni, Fe, and Co) have been refined: (Ca0.12?0.88)(Al1.69Ni 0.81 2+ Fe 0.50 2+ )(Al5.40Fe 0.60 3+ )(Si5.82Al0.18O18)(BO3)3(OH)3.25O0.75 I, a = 15.897(5), c = 7.145(2) Å, V = 1564(1) Å; Na0.91(Ni 1.20 2+ Cr 0.96 3+ Al0.63Fe 0.18 2+ Mg0.03)(Al4.26Ni 1.20 2+ Cr 0.48 3+ Ti0.06)(Si5.82Al0.18)O18(BO3)3(OH)3.73O0.27 II, a = 15.945(5), c = 7.208(2) Å, V = 1587(1) Å3 and Na0.35(Al1.80Co 1.20 2+ )(Al5.28Co 0.66 2+ Ti0.06)(Si5.64B0.36)O18(BO3)3(OH)3.81O0.19 III, a = 15.753(8), c = 7.053(3) Å, V = 1516(2) Å3. The reliability factors are R 1 = 0.038?0.057 and wR 2 = 0.041–0.060. It is found that 3d elements occupy both Y- and Z positions in all structures. The excess positive charge is compensated for due to the incorporation of divalent oxygen anions into the O3(V)+O1(W) positions. 相似文献
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The crystal structure of natural titanium-containing ludwigite has been refined. The unit-cell parameters are a = 9.260 ± 0.002 Å, b = 12.294± 0.002 Å, c = 3.0236± 0.0005 Å, sp. gr. Pbam, and R = 0.0288. The observed cation distribution over the M1-M4 positions corresponds to the structural formula (Mg0.5)(Mg1.0)(Mg0.338Fe 0.162 2+ )(Fe 0.47 3+ Ti 0.21 4+ Mg 0.15 2+ Al 0.10 3+ Fe 0.07 2+ (BO3)O2. Highly charged titanium ions in the M4 position are balanced mainly with magnesium and not with divalent iron ions. 相似文献