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151.
Marek Dabrowski Sergiusz Lulinski Janusz Serwatowski Magdalena Szczerbinska 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(12):o702-o704
The structure of the title compound, 2‐CH3O‐C5H3N–3‐B(OH)2 or C6H8BNO3, comprises two crystallographically independent molecules. The molecules are linked to each other by intermolecular O—H⋯N and C—H⋯O bonds to produce an infinite chain, while a two‐dimensional structure is formed as a result of π–π interactions of planar molecules. 相似文献
152.
M. Barczak A. Dabrowski J. Ryczkowski S. Pasieczna-Patkowska 《The European physical journal. Special topics》2008,154(1):301-304
Bridged polysilsesquioxane xerogels containing amine, thiol, acethoxy and urea groups were synthesized by co-condensation
of
ethylene-bridged monomer, and appropriate alkoxysilanes in the presence of a
fluoride-ion catalyst in an ethanol solution. FT-IR/PA spectroscopy was used
to determine the chemical composition of the final materials. FT-IR/PAS data
testify that all xerogels contain residual silanol groups and some fraction
of non-hydrolyzed ethoxygroups. The same data show that amino groups form
hydrogen bonds. 相似文献
153.
Hajer H. M. Elkhalgi Sarita Khandka U. B. Singh K. L. Pandey R. Dabrowski 《Liquid crystals》2013,40(12):1795-1801
ABSTRACTWe have prepared the composites of a room temperature nematic liquid crystalline material namely 4-(trans-4′-n-hexylcyclohexyl) isothiocyanatobenzoate (6CHBT) and gold nanoparticles (GNPs). Thermodynamic, electro-optical and dielectric properties have been investigated. Effect of dispersion of GNPs on various electro-optical and display parameters of host liquid crystalline material have been studied. Physical parameters such as threshold voltage, dielectric anisotropy and splay elastic constant have altered for composite systems. Due to the dispersion of GNPs, nematic to isotropic transition temperature is significantly increased. Relaxation frequency corresponding to flip-flop motion of the 6CHBT molecules about their short axes has increased due to the presence of GNPs. 相似文献
154.
Thermodynamic, dielectric, optical and switching parameters of a single-phase antiferroelectric (AF) liquid crystalline material (S)-(+)-4-(1-methylheptyloxycarbonyl)-2,3-difluorophenyl 4′-[3-(2,2,3,3,4,4,4-heptafluorobutoxy)prop-1-oxy]biphenyl-4-carboxylate have been studied. These studies show wide temperature range (~97.8°C–25.3°C) of AF SmC*A phase in the material. The dielectric studies have been carried out in the frequency range of 1 Hz–35 MHz under planar anchoring conditions of the molecules. The dielectric spectrum of the SmC*A phase exhibits three relaxation modes due to the collective as well as individual molecular processes. Relaxation frequencies of these modes lie in the range of kHz–MHz regions. Relative permittivity of the material (at 10 kHz) varies from ~8.8 at 98.8°C to 9.9 at 41.0°C. Maximum tilt of the molecule in the SmC*A phase is ~43°C. Spontaneous polarisation, switching time and rotational viscosity have also been determined. The maximum value of PS is ~439 nC/cm2 and switching time is the order of 1–5 millisecond, whereas viscosity is moderate. 相似文献
155.
Enhanced electro-optical properties of a nematic liquid crystals in presence of BaTiO3 nanoparticles
Composites of nematic liquid crystals (NLCs) and ferroelectric barium titanate (BaTiO3) nanoparticles (NPs) have been prepared. The alignments of NPs in the host medium have been demonstrated. Effect of NPs doping on various display parameters of NLCs, namely, threshold voltage, dielectric anisotropy and splay elastic constant has been studied using electro-optical and dielectric studies. The nematic ordering of host supports alignment of NPs parallel to the director which consequently improves electro-optical parameters in the composite system. The dielectric and electro-optic properties of LC–NPs composites have been discussed in frame of conventional theories of NLCs. 相似文献
156.
Z. Raszewski J. Rutkowska J. Kedzierski J. Zieliński J. Żmija R. Dabrowski 《Liquid crystals》2013,40(6):1715-1723
Abstract Measurements of complex electric permittivity of room temperature ferroelectric liquid crystal mixtures have been made on aligned samples with the electric measuring field being parallel to the layer planes. The spontaneous polarization, the tilt angles and pitch have been measured in these mixtures. By theoretical fitting of the experimental points of electric permittivity for the Cole–Cole modification of the Debye equation dielectric parameters, the dielectric strength, relaxation frequency, and distribution parameter for the Goldstone mode have been computed. The dielectrically observed Goldstone mode in our mixtures is shown to have both DC bias field and AC field dependences. 相似文献
157.
O. A. Dudarko Yu. L. Zub A. Dabrowski M. Barczak 《Russian Journal of Applied Chemistry》2008,81(1):114-122
Formation of bifunctional xerogels containing -NH2, -SH, -P(O)(OEt)2, and -NHP(O,S)(OEt)2 complexing groups in the surface layer was studied using sol-gel method (fluoride ion catalyst, ethanol solvent) and three-component systems. 相似文献
158.
Binary mixtures in which one component is nCBB or its chiral analogue, and the second component is nCB, nOCB, n.CN, or one of their chiral analogues are studied by thermomicroscopy. The branched compounds induce the smectic Ad phase more strongly than unbranched compounds with the same alkyl chain length. The observed behaviour is discussed from the point of view of dimer formation. In all chiral systems, the TGBA phase appears. 相似文献
159.
C. W. Kimball B. Dabrowski Yuehai Liang Weimin Peng B. D. Dunlap 《Hyperfine Interactions》1992,72(1-3):153-172
A Mössbauer study has been made on57Fe ions substituted into the Cu(1) site of REBa2Cu3?x Fe x O7+δ (RE=Y, Er, Dy, Gd;x=0.15, 0.30). At low temperature, the iron atoms antiferromagnetically order with a transition temperature which is dependent on the Fe concentration. The temperature dependence of the magnetic subspectra representing Fe ions with various local oxygen environments in YBa2Cu3?x Fe x O7+δ and ErBa2Cu3?x Fe x O7+δ fit a 2D-Ising model with a ratio of the anisotropic exchange between the two directions on the order of 0.5–1.0(10?3) for the Y-compounds and on the order of 1 for the Er-compounds. The magnitude of the local dopant magnetization is related to a short-range chemical order which determines the magnetic chain size and defines the correlation lengths. For the Y-compound, the order is quasi-1D with strong intrachain but very weak interchain coupling. For the Er-compounds, the magnetic coupling is Ising 2D. The strong fluctuation behavior expected in low dimensional systems above and belowT N is observed via characteristic relaxation in the Mössbauer linewidth nearT N. For both the Dy- and Gd-compounds, the magnetic order is 3D. The magnitude of the rare-earth magnetic moments appears to affect the character of the magnetic interaction in the Cu(1)-site. However, a Mössbauer effect measurement at155Gd nuclei in GdBa2Cu2.85Fe0.15O7+δ (T N(Fe)~14 K) shows paramagnetic behavior at 4.9 K. 相似文献
160.
The left regular representation of the quantum algebras sl
q
(2) and e
q
(2) are discussed and shown to be related by contraction. The reducibility is studied andq-difference intertwining operators are constructed. 相似文献