Experimental Investigations of the Conditions for the Formation of the Liquid Crystalline State of Polymers

The diagrams of state for concentrated PBG solution in coordinates relating volume fraction-geometric asymmetry and volume fraction-temperature are investigated. The order parameter for macromolecules in the anisortropic phase is dettermined. The experimental data compare with the existing theoretical models for th formation of the liquid crystalline state in solutions of stiff polymer molecule. It is shown that experimental data are in good quantitative agreement with the Flory's lattice model.     

Formation of the Liquid Crystal of a Surface-active Dye in Aqueous Methanol Solutions

The formation of the liquid crystal phase of a surface-active dye, p-octylphenol yellow amine poly(ethylene oxide), in aqueous methanol solutions has been examined by optical microscopy. Rodlike swarms appear at relatively low dye concentrations only slightly higher than the second critical micelle concentration. They develop into liquid crystal phase when the dye concentration is further increased. It takes some hours for the formation of a stripe-like texture characteristic of nematic liquid crystals, depending on the methanol content and dye concentration. The combination of the surface active-part and the azobenzene moiety would be responsible for the formation of the liquid crystal.     

Mixed Dimer Formation in Binary and Ternary Mixtures of Liquid Crystalline 4-Substituted Benzoic Acids

Mixed dimer formation is studied for a wide variety of 4-substituted benzoic acids that form liquid crystalline phases. The solid-mesophase transitions can show double eutectics when mixed dimer formation occurs, but in many cases the equilibrium constant for such a mixed dimer is extremely small. The mesophase-isotropic transitions are essentially linear over the entire phase diagram. Ternary mixtures can be created having nematic ranges of over 80° by virtue of eutectization.     

H2O/HAc对纳米TiO2/硅藻土复合材料TiO2晶相和性能的影响

以硅藻土为载体,钛酸四丁酯为前驱体,采用溶胶-凝胶法制备了纳米TiO2/硅藻土复合材料.在750下对复合材料煅烧晶化,以罗丹明B为降解对象检测了材料的光催化性能.并结合XRD、BET、SEM等表征手段,探究了H2O/HAc比例对复合材料晶型、比表面积和光催化性能的影响.结果表明,H2O/HAc比例对TiO2/硅藻土复合材料中TiO2的晶相组成和光催化性能有很大影响.当H2O/HAc=6时,二氧化钛颗粒均匀地负载在硅藻土表面,样品具有较大的比表面积和较好的光催化效果,同时锐钛矿晶型比例为80.2;.     

Formation of Hydrogen-Bonding Adduct between 1-Phyenyl-2-Amino Pyrimidine and Vaniline,C17H13N3O2

The adduct compound was prepared by condensation of equimolar quantities of analar vaniline and 1-phenyl-2-amino pyrimidine in absolute ethyl alcohol. Prismatic crystals were obtained with the crystallographic data: a = 12.901 (6), b = 19.297 (9), c = 6.828 (3) Å, γ = 102.67 (2)°, V = 1657.9 ų, Z = 4, F.W. = 291.31, D_x = 1.17 g/cm³, space group P2/n, R = 0.038 and R_w = 0.036. The intensity data were collected on an Enraf Nonius CAD-4 computer controlled diffractometer using MoKα radiation. The structure was solved by direct method and refined by full matrix least-squares using anisotropic temperature factor of all atoms, except for hydrogen ones, which were treated isotropically. A full discussion was given to explain: a) the occurrence of the condensation process between the OH-group of vaniline and the heterocyclic N-atom in position 5 of the pyrimidine cycle and b) why this condensation does not take place between the amino-group of the pyrimidine compound and the aldehydic group of vaniline to give a Schiff base.     

Selective etching of ZnTe in HF:H2O2:H2O solution: Interpretation of extended defect‐related etch figures

HF:H₂O₂:H₂O solution (40%wt.HF: 30wt.%H₂O₂: H₂O, 3:2:1 by volume) was used to reveal extended defects (line, face and volume defects) in bulk ZnTe crystals grown from Te solution. The etch patterns were analyzed based on their size, shape and distribution. The etch figures, both in the shape of pits and hillocks with high resolution, show forms controlled by the symmetries of the respective faces were produced. Two different sizes of pits were observed, the larger‐size pits correspond to dislocations penetrating the surface, however, the smaller‐size texture pits are produced on the defect‐free region, which serve as standard pits on respect faces. The face defects, such as grain boundaries, sub‐grain boundaries, dislocation walls, twins and stacking faults, can be all displayed clearly. Another essential feature of the etchant is that, it can effectively dissolve Te‐rich phase (Te inclusion/precipitates), which makes it promising to reveal the shape of this volume defect.     

Isotope Effects in Liquid Crystal Systems: I: Phase Relationships in the Dodecylamine-H2O,Dodecylamine-D2O Systems

The phase diagrams and heats of fusion and transition have been determined for the dodecyl amine (-NH₂)/H₂O and dodecyl amine (-ND₂)/D₂O systems using direct optical observation and differential scanning calorimetry.     

The Structure of a Lyotropic Liquid Crystalline Phase that Orients in a Magnetic Field

Abstract

The structure of a lyotropic liquid crystalline phase with positive diamagnetic anisotropy (type I), that spontaneously orients in a magnetic field has been studied by means of water NMR quadrupole splittings, NMR diffusion and polarized absorption spectroscopy. It is concluded that this phase is built up of long rodlike aggregates. A preliminary study of a sample with negative diamagnetic anisotropy (type II) shows that this phase probably consists of lamellar aggregates. It is suggested that these phases are suitable as orientation matrices for studies of chromophores with polarized light spectroscopy.     

Vacuum-ultraviolet absorption of interstitial O2 and H2O molecules in SiO2 glass

Vacuum-ultraviolet (VUV) absorption of O₂ and H₂O molecules incorporated in interstitial voids in SiO₂ glass by thermal annealings was examined. Interactions of the interstitial molecules with the surrounding SiO₂ glass network lead to a redshift of the VUV absorption band of interstitial O₂, while a blueshift of that of interstitial H₂O, both accompanied by an increase in the intensity of the absorption bands. The Coulomb repulsion, London dispersion, and hydrogen bonding are the main interactions responsible for the modification of the VUV absorption bands.     

Electrical Conductivity and Thermal Dehydration Studies of Mixed Single Crystals of BaCu(C2O4)2 · 6 H2O,Ba1–xCuxC2O4 · 4 H2O and Ba1–2x(NH4)2xC2O4 · 4 H2O

The measurement of electrical conductivity for the investigation of the number of water molecules present in the mixed crystals of barium copper oxalate and barium ammonium oxalate lattice have been carried out in the temperature range 30 to 450 °C. The dehydration temperature and the number of water molecules removed out of the structure at a particular temperature is estimated from the sharp increase in conductivity at these points. The almost steep increase of conductivity is attributed to the increase in the number of mobile charge carriers H⁺ and OH^– ions generated from the escaping water molecules. The study of electrical conductivity in association with the thermal behaviour has been used to understand the mechanism of conduction.     

Enthalpies of Lyotropic Liquid Crystalline Phases. : 2. The Partial Molar Enthalpies of the Lamellar and Hexagonal Phases in the System N-Pentanol-Sodium N-Octanoate-Water

The relative partial molar enthalpies of the components in the system N-pentanol-sodium N-octanoate-water (C₅OH-NaC₈-H₂O) have been determined in the lamellar (D-) and hexagonal (E-) liquid crystalline phases formed in this system at 25°C. The enthalpies are correlated with Bragg spacings and earlier nmr studies. They indicate that (a) the minimum amount of water needed to hydrate the polar groups limits the region of existence of both D- and E-phase towards low water contents, (b) the interaction between -OH and -COO is especially important in stabilizing the D-phase containing large amounts of water, (c) the Bragg spacings and the enthalpies both change their concentration dependence markedly when the maximum amount of water that can be bound by primary hydration of the polar groups and the counter ions in the D-phase is exceeded, (d) enthalpies of transition from one phase to another are small compared to enthalpy changes with composition within the phases; the same holds for Bragg spacings. Hence, the composition of the sample (above all, the mole fraction of NaC₈) is more important than the phase structure in determining these properties. It is obvious that further studies of enthalpies in similar systems can give important information on the factors governing phase stabilities and structural changes within the phases.     

Amplitude Modes in Mixed Polymers Trans [C2H2)y(C2D2) 1-y]x

Resonant Raman Scattering and doping induced IR absorption are explained in terms of amplitude modes of the 1-d gap. The RRS frequencies and relative intensities of the renormalized phonon lines at the various concentrations are readily obtained.     

Hydrothermal synthesis and structure of a novel terbium coordination polymer with packing cavities, {[Tb(TCB)1/2(H2TCB)1/2(H2O)](H2O)2}n (H2TCB = 1, 2, 4, 5‐benzenetetracarboxylic acid)

A novel terbium coordination polymer {[Tb(TCB)_1/2(H₂TCB)_1/2(H₂O)](H₂O)₂}_n (H₂TCB = 1, 2, 4, 5‐benzenetetracarboxylic acid) ( 1 ) has been hydrothermally synthesized and determined by single crystal X‐ray diffraction method, which features a very interesting three‐dimensional framework with large packing cavities. It crystallizes in the monoclinic space group P2₁/n with a = 1.0723(4) nm, b = 0.7168(3) nm, c = 1.7155(6) nm, β = 97.079(4)°, V = 1.3086(8) nm³, Z = 4, and final R₁ = 0.0203, wR₂ = 0.0404. In 1, the protonated carboxylate groups are free, the other carboxylate groups are bonded to Tb³⁺ ion in three modes: the chelating bidentate, the bridging bidentate and bridging tridentate. Moreover each Tb³⁺ ion is coordinated by nine oxygen atoms from six carboxylate groups and one water molecule respectively to complete a deformed tricapped trigonal prismatic geometry. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structures of two local anesthetics: Dibucaine·HCl·H2O and Dimethisoquin·HCl·H2O

The crystal structures of the tertiary amine local anesthetics dibucaine hydrochloride monohydrate (C₂₀H₂₉N₃O₂·HCl·H₂O) and dimethisoquin hydrochloride monohydrate (C₁₇H₂₄N₂O·HCl·H₂O) have been determined. Dibucaine forms crystals inP2₁/c witha=10.669(3),b = 35.981(5),c= 11.417(2) Å,= 89.654(3) ° andZ= 8. Dimethisoquin crystallizes in the space groupP¯1 witha = 5.338(6),b=7.579(8),c= 22.336(24) Å,a = 85.513(1), = 87.447(1), =84.863(1) °, andZ=2. Intensity data were collected with an automatic diffractometer, using CuK for dibucaine and MoK for dimethisoquin. The structures were solved using direct methods and refined by full-matrix least-squares procedures to final values ofR= 12.8% for dibucaine andR = 8.8% for dimethisoquin. The structures of both local anesthetics feature planar fused ring systems and extended side chains, one of which contains the tertiary amine that forms hydrogen bonds with other local anesthetic molecules and the chlorine and solvent atoms. The possible sites of action of the anesthetics in the cell membrane are discussed on the basis of these structures.     

Blends of Poly(Buty1ene Terephthalate) with Thermotropic Liquid Crystalline Polyesters. Morphology and Thermal Behavior

Blends of poly(butylene terephthalate) with liquid crystalline poly (decamethylene 4, 4′-terephthaloyldioxydibenzoate) were studied in all the composition range by optical and electron microscopy and differential calorimetry. The morphology and phase transitions of the blends are markedly influenced by the composition and thermal history. The results suggest the occurrence of miscibility phenomena between the two components in the amorphous phase.     

Ti-Al-Nb2O5系原位合成Al2O3晶须的形成机理分析

本文研究了以粉埋法原位合成的Al2O3晶须的形态和反应过程以及晶须的生长机理.通过物相测试表明产物由Al2O3、TiAl3、NbAl3和少量的AlN相组成,SEM结合EDS分析表明原位合成了直径小于100nm的Al2O3晶须,晶须呈棉絮状分布于基体交界处.基于铝的过剩,TiAl3相是Ti-Al界面的唯一产物.Ti与O2以反应时间短的动力学势优先形成的TinOm中间产物是Al2O3晶须生成的控制步骤.Nb2O5与铝液的双效复合催化作用,提高了晶须的生成速率;同时Al的用量因AlN的生成而减小,导致生成晶须的催化活性点减小,而扩散到每个活性点周围的TinOm及Nb2O5浓度增加,导致晶须分布密而均匀.Al2O3晶核在催化剂的作用下以螺旋位错生长形成长径比较为理想的Al2O3晶须.     

Structure of a potent neuromuscular blocking agent: Caracurine-II dimethochloride octahydrate, [C40H44N4O2]2+·2CI−·8H2O

Crystals of this calabash curare alkaloid, space groupP2₁; havea=12.695(4), Å,b=7.424(2) Å,c=21.762(6) Å,=98.03(5)°,Z=2,F(000)=884. The structure was solved by direct methods and refined by least squares toR=0.10. The alkaloid cation, with two-fold molecular symmetry, has a highly fused ring system and is structurally rigid. This determination provides accurate stereochemical parameters for those atoms and groups (N⁺ centers, aromatic rings, and hydrogen bond acceptors) postulated by various theories as involved in binding to the acetylcholine receptor. In the crystal, layers of alkaloid cations parallel to thebc plane alternate with layers containing two Cl^– ions and eight water molecules distributed almost randomly over ten sites. Electrostatic attractions between N⁺ and Cl^– bind the alternating layers together. Each one of the ten sites is, on average, 4.60 Å from one or two N⁺, allowing the two Cl_– ions to be disordered. Binding interactions within the alkaloid layers are solely van der Waals attractions. Within each H²O/C1^– layer there is a complex hydrogen bond system, including four infinite spirals parallel to theb axis, with an average bonding distance of 2.94 Å. There are no hydrogen bonds between layers. The possible relevance to the activity of the alkaloid of its ability to organize large amounts of water is discussed.     

Na2CaSi2O6–P2O5 based bioactive glasses. Part 1: Elasticity and structure

The glass structure and elastic properties of two bioglasses having bulk compositions near Na₂CaSi₂O₆ (45S5.2) and Na₂CaSi₃O₈ (55S4.1) were studied using both Raman and Brillouin scattering techniques. The annealed 45S5.2 glass has more Q² and Q⁰ but less Q³ species than 55S4.1 glass due to lower (Si⁴⁺ + P⁵⁺)/(Na⁺ + Ca²⁺) ratio. Brillouin scattering measurements of the as-annealed glasses indicated that 45S5.2 glass is ca. 2% and 9% higher in Young’s and bulk moduli than 55S4.1 glass due to more modifiers in the 45S5.2 glass. Nearly full crystallization of 45S5.2 glass was observed after treating it at 715 °C for ca. 30 min. Devitrification of the 45S5.2 glass caused an increase in the elastic moduli up to ca. 30% (fully crystallized) but a negligible change in density. This 45S5.2-derived crystalline phase displayed at least 17 Raman bands, and has the average elastic moduli of 72.4 (bulk), 41.6 (shear), and 104.7 (Young’s) GPa. The comparable elastic moduli with hydroxyapatite and the ability for developing a HCA layer in simulated body fluid indicate that the 45S5.2-derived phase may be better for using as a substitute of bone than its parent glass.