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1.
The title compound, 4-(cholestroxycarbonyl)pentyloxy-4'-heptyloxycarbonylbiphenyl (C53H78O5), is a novel dimesogen comprising two mesogenic units dissimilar in nature. It crystallizes in the orthorhombic space group P212121 with cell parameters a = 6.241(3), b = 17.943(5), c = 43.13(5), Z = 4. The structure was solved using SHELXS (Sheldrick, 1997) and refined using SHELXL (Sheldrick, 1997). The final residual was R = 0.0803 for 1769 reflections with I < 2 σ(I). In the crystal phase the molecule is linear and the terminal groups show stretching with higher bond distances. The packing of the molecules shows imbrication, herringbone and stacking along the a, b, and c axes, respectively. The structure also exhibits an intermolecular hydrogen bond of the type CH…O. The space group suggests the possibility of a chiral mesophase. 相似文献
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The Merck nematic mixture E49 exhibits a large nematic interval (0–100 °C) and a large dielectric anisotropy. Both of these features make E49 interesting for applications and basic physics. Unfortunately, no systematic measurements of the material constants of this mixture and their temperature dependence have been reported in the literature. In this paper we report experimental measurements of the splay and bend elastic constants (K 11 and K 33) of the ordinary and the extraordinary refractive indices (n ort and n par) at the wavelength λ?=?632.8 nm and of the two elastic constants parallel and orthogonal to the director (εpar and εort) at the frequency ν?=?5?kHz. The temperature dependence of all of these parameters is found in the temperature range 25–99 °C. The measurements of the elastic constants are performed using both a dielectric and an optical method simultaneously on the same nematic sample. The results obtained using the two methods are in a satisfactory agreement between them within the estimated experimental uncertainty. The ordinary and the extraordinary indices are measured using the prism method. 相似文献
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Gia Petriashvili Maria Penelope De Santo Lali Devadze Tsisana Zurabishvili Nino Sepashvili Ramla Gary Riccardo Barberi 《Macromolecular rapid communications》2016,37(6):500-505
Rewritable optical storage has been obtained in a spiropyran doped liquid crystal polymer films. Pictures can be recorded on films upon irradiation with UV light passing through a grayscale mask and they can be rapidly erased using visible light. Films present improved photosensitivity and optical contrast, good resistance to photofatigue, and high spatial resolution. These photochromic films work as a multifunctional, dynamic photosensitive material with a real‐time image recording feature.
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G. Barbero 《Liquid crystals》2013,40(10):1370-1381
Elastic energy terms linear in the deformation tensor can appear in an ultrathin layer at the interface of a nematic liquid crystal with a substrate. These Lifchitz invariant like terms can destroy an initially uniform alignment. In particular, they can induce modulated structures. The instability towards a periodic deformation of the nematic director can occur only if the anchoring energy is lower, and the elastic constant of the Lifchitz term is larger than well-defined critical values. The present phenomenological model accounts for experimental observations where a homeotropic slab undergoes, upon cooling, a tilt transition followed by a structural transition towards a stripe texture. 相似文献
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N. K. Lokanath M. A. Sridhar D. Revannasiddaiah J. Shashidhara Prasad 《Liquid crystals》2013,40(6):767-774
The title compound, 4-n-nonylbenzoic acid, CH3(CH2)8C6H4COOH (NBA), has been characterized thus: triclinic, P1, a = 13.514(4)Å, b = 23.4672(5)Å, c = 7.658(3)Å, alpha = 90.914(3)°, beta = 100.403(3)°, gamma = 77.781(2)°, V = 2334(2)Å3, Z = 2, and F.W = 745.06, Dm = 1.161 g cm-3, Dc = 1.061 g cm-3, F000 = 816.00, lambda = 0.71069Å, mu = 0.6 cm-1, goodness-of-fit is 1.029, final R1 = 0.063 and wR2 = 0.16. 相似文献
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《Electroanalysis》2006,18(16):1558-1563
Liquid crystal templating has been used to produce metal films with nanometer‐sized pores. While successful templating procedures have been reported for metals from some groups of elements (e.g., groups 9 and 10), no such reports are available for other groups. This work investigates liquid crystal templating procedures for metals from groups 11 and 12. TEM indicates that permanent mesoporous structures are obtained for templated cadmium while copper forms mesoporous structures only temporarily. Silver, gold and zinc could not be templated at all. Reasons for these observations are briefly discussed, underlining the importance of various factors influencing the templating process. 相似文献
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Direct Anisotropic Growth of CdS Nanocrystals in Thermotropic Liquid Crystal Templates for Heterojunction Optoelectronics 下载免费PDF全文
Kai Yuan Prof. Dr. Lie Chen Prof. Dr. Yiwang Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(36):11488-11495
The direct growth of CdS nanocrystals in functional solid‐state thermotropic liquid crystal (LC) small molecules and a conjugated LC polymer by in situ thermal decomposition of a single‐source cadmium xanthate precursor to fabricate LC/CdS hybrid nanocomposites is described. The influence of thermal annealing temperature of the LC/CdS precursors upon the nanomorphology, photophysics, and optoelectronic properties of the LC/CdS nanocomposites is systematically studied. Steady‐state PL and ultrafast emission dynamics studies show that the charge‐transfer rates are strongly dependent on the thermal annealing temperature. Notably, annealing at liquid‐crystal state temperature promotes a more organized nanomorphology of the LC/CdS nanocomposites with improved photophysics and optoelectronic properties. The results confirm that thermotropic LCs can be ideal candidates as organization templates for the control of organic/inorganic hybrid nanocomposites at the nanoscale level. The results also demonstrate that in situ growth of semiconducting nanocrystals in thermotropic LCs is a versatile route to hybrid organic/inorganic nanocomposites and optoelectronic devices. 相似文献
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Yuichiro Haramoto Taito Yamada Masato Nanasawa Masahiro Funahashi Junichi Hanna Seiji Ujiie 《Liquid crystals》2013,40(8):1109-1111
New conductive thermotropic liquid crystalline materials having a piperazine ring in the central core: 1-[4-(9-decenyloxy)phenyl]-4-alkylpiperazines (6) were synthesized. The mesomorphic behaviours of these compounds and their conductivity in the liquid crystal phase were measured. The principal features of these compounds are to exhibit a smectic B phase around room temperature (for example 6: Cr 50 SmB 81 I, °C) and to exhibit a large dark current (6d: 430 μA cm?2, applied voltage 20 V, at 70°C) in the smectic B phase. 相似文献
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F. Mercuri M. Marinelli U. Zammit F. Scudieri 《Journal of Thermal Analysis and Calorimetry》1998,52(3):739-744
Thermal conductivity (k) and thermal diffusivity (D) of the 9CB liquid crystal have been simultaneously determined by a photopyroelectric
(PPE) technique in the temperature range from 308 K to 332 K where two different phase transitions occur. The measurements
have been performed on oriented samples and the k and D anisotropy has been studied. The behaviour of the macroscopic order
parameter vs. temperature has been determined and the order of the phase transitions checked.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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P. J. Sebastião C. Cruz D. Pires A. Ferraz P. Brogueira M. H. Godinho 《Liquid crystals》2013,40(12):1491-1495
Hydroxypropylcellulose films are used as the alignment substrate in a liquid crystal bistable electro-optical device. These alignment films were characterized by atomic force microscopy. The electro-optical behaviour of this device, which operates in the Clark-Lagerwall mode, is identical to that observed for typical SSFLC cells. In particular the bistability of the cell was clearly observed, the threshold voltage was measured and an estimation of the anchoring energy of the LC mixture used, in this type of system, was made. 相似文献
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Liquid-crystalline rigid-core semiconductor oligothiophenes: influence of molecular structure on phase behaviour and thin-film properties 总被引:1,自引:0,他引:1
Melucci M Favaretto L Bettini C Gazzano M Camaioni N Maccagnani P Ostoja P Monari M Barbarella G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(36):10046-10054
The design, synthesis and properties of liquid-crystalline semiconducting oligothiophenes containing dithienothiophene (DTT), benzothiadiazole (BTZ) and carbazole (CBZ) rigid cores are described. The effect of molecular structure (shape, size and substitution) on their thermal behaviour and electrical properties has been investigated. Polarised optical microscopy (POM) and differential scanning calorimetry (DSC) analyses have revealed highly ordered smectic mesophases for most of the newly synthesised compounds. X-ray diffraction (XRD) studies performed at various temperatures have shown that the smectic order is retained in the crystalline state upon cooling across the transition temperature, affording cast films with a more favourable morphology for FET applications. 相似文献
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Celebre G Concistrè M De Luca G Longeri M Pileio G Emsley JW 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(12):3599-3608
The (1)H NMR spectrum of a sample of acrolein dissolved in the nematic liquid crystal phase I52 has been analysed to yield 18 dipolar couplings between all the magnetic nuclei in the molecule; moreover, the (13)C and (13)C{(1)H} NMR spectra of a sample of acrolein in CDCl(3) were recorded and analysed to determine the indirect J(ij) couplings. The data were used to obtain the relative positions of the carbon and hydrogen atoms, assuming that these are independent of the conformations generated by rotation around the C--C bond through an angle phi, and to obtain a probability distribution P(phi). It has been found that in the liquid phase, the distribution is a maximum at the trans form whereas the abundance of the cis form is significantly smaller compared with that found by microwave spectroscopy or high level quantum mechanical calculations. Such calculations produced also a suitable force field needed to develop suitable strategies for vibrational correction procedure in the case of flexible molecules. 相似文献
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Zizi Sideratou Dimtris Tsiourvas George Pistolis Constantinos M. Paleos 《Journal of inclusion phenomena and macrocyclic chemistry》1996,24(3):219-232
The hydrogen bonding interaction ofp-anisidine andN-methyl-p-anisidine withp-alkoxybenzoic acids has been investigated in the bulk and in solution. As established by FT-IR and NMR spectroscopy, this interaction is effective in aprotic solvents, leading to the formation of hydrogen bonded complexes. In the melt, complex formation does not proceed to a significant extent, apparently due to the immiscibility of the two components, as shown by FT-IR spectroscopy and also proved by the phase diagrams obtained for these components. Thus the liquid crystalline phases that were observed originated from the dimeric acids which form a separate phase within the phases of melted anisidines. 相似文献
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