Influence of Intra-Molecular Conformational Transitions and some Physico-Chemical Quantities of Liquids on their Thermal Conductivity

It is shown that the thermal conductivity of various liquids can be described adequately by taking into account the influence of intra-molecular conformational transitions on the number of bimolecular collisions in the liquid phase. The proposed equations allow the calculation of this transport property at different temperatures.     

Viscosity of Near-Boiling NonAssociated Liquids: Dependence on Surface Tension,Molecular Mass and IntraMolecular Conformational Transitions

The equation proposed for near-boiling nonassociated liquids describes a new functional dependence of their viscosity on such physico-chemical characteristics as surface tension and molecular mass. It is shown that the viscosity of liquids with conformationally flexible molecules can be calculated adequately by taking into account the influence of intramolecular conformational transitions on the number of bimolecular collisions in the liquid phase.     

Two-Dimensional Supramolecular Polymerization of a Bis-Urea Macrocycle into a Brick-Like Hydrogen-Bonded Network

We report on a dendronized bis-urea macrocycle 1 self-assembling via a cooperative mechanism into two-dimensional (2D) nanosheets formed solely by alternated urea-urea hydrogen bonding interactions. The pure macrocycle self-assembles in bulk into one-dimensional liquid-crystalline columnar phases. In contrast, its self-assembly mode drastically changes in CHCl₃ or tetrachloroethane, leading to 2D hydrogen-bonded networks. Theoretical calculations, complemented by previously reported crystalline structures, indicate that the 2D assembly is formed by a brick-like hydrogen bonding pattern between bis-urea macrocycles. This assembly is promoted by the swelling of the trisdodecyloxyphenyl groups upon solvation, which frustrates, due to steric effects, the formation of the thermodynamically more stable columnar macrocycle stacks. This work proposes a new design strategy to access 2D supramolecular polymers by means of a single non-covalent interaction motif, which is of great interest for materials development.     

液体分子自扩散系数的预测

基于液体层膜结构模型提出预测液体分子自扩散系数的方程,对24种液体在较宽温度范围内作了检验,平均偏差为3.8%。同时分析了层膜结构模型中位形参数ξ随温度和物质不同而变化的规律,这对了解液体的微观结构、扩散过程的机理和阐明层膜结构模型的合理性具有重要意义。     

Advanced Materials: Trends and Possibilities in Liquid Crystalline Polymers

During the past ten years there has been a sharp increase in interest in the opportunities afforded by R & D in the field of specialty polymers. Interest is mainly being shown in two distinct categories of polymers, namely, (a) polymers which are used in very small quantities to fulfill critical needs as a part of device system, and (b) high-performance engineering polymers which significantly extend their mechanical and thermal properties for structural applications. The first category ranges from advanced resists and insulating layers for microelectronic devices to membranes for filtration systems. The second category encompasses improved matrices for advanced composites as well as liquid crystalline polymers. In the present paper an overview is first given of the emerging opportunities for advanced materials and particularly specialty polymers. The status of work on liquid crystalline copolyesters is then discussed with special emphasis on one of the major problems confronting this field, namely interpreting the microstructure of the copolyesters.     

The Packing Coefficient of Liquid 2-Phenylnaphthalene Molecules at 396 K

A method of measuring the angular intensity distribution of monochromatic MoK f radiation, u = 0.71069 Å scattered by a thin layer of liquid 2-phenylnaphthalene C 10 H 7 -C 6 H 5 is proposed and results of such an experiment are presented. Fourier analysis of this distribution by the procedure of Warren-Krutter-Morningstar yielded electron-density radial-distribution function (EDRDF). The curve of radiation intensity was analysed by the pair functions method. The determined mean, mutual distances between molecules of liquid studied are: [rbar] 1 = 5.30 Å, [rbar] 2 = 7.43 Å, [rbar] 3 = 12.35 Å. X-ray structural analysis was applied to determine the packing coefficient of 2-phenylnaphthalene molecules at 396 K. From the known volume of the first coordination sphere as well as the specific volume of the molecule V 0 and taking into regard the structural model of intermolecular interactions, the most probable value of the packing coefficient of the molecules was found to be [kbar] = 0.64. This value falls in the range of [kbar] values permissible for liquid phase. The results concern a wide class of molecular liquids, in particular polar compounds being naphthalene derivatives.     

离子液体对锯末中纤维素的溶解及再生研究

探讨了离子液体1-(4-磺酸基丁基)-3-甲基咪唑的硫酸氢盐(IL-1)作为催化剂,金属氯化物作为助催化剂时纤维素的水解,利用离子液体IL-1对杨木锯末中纤维素的直接溶解并再生,考察了温度、碱性溶液的浓度以及溶解时间对溶解率的影响,通过傅里叶红外光谱FT-IR、X-射线衍射仪及热失重对处理前后锯末、再生纤维素的结构、结晶性及热性能进行了研究.结果表明,温度为90℃,NaOH质量分数为6%,溶解时间为2 h时,离子液体对杨木锯末具有最佳的溶解性,溶解率可达45%左右.离子液体主要溶解杨木锯末中的纤维素,且为非衍生化的直接溶解,再生后的纤维素结晶形态由纤维素I变为II,热稳定性能有所降低.     

手性离子液体在有机合成中的应用

近年来,手性离子液体的应用研究取得了重要进展,新的手性离子液体的不断涌现促使人们对其应用研究的兴趣不断提高.本文综述了手性离子液体在有机合成中应用研究的新进展.     

Thermo- and Photocatalytic Activation of CO2 in Ionic Liquids Nanodomains

Ionic liquids (ILs) are considered to be potential material devices for CO₂ capturing and conversion to energy-adducts. They form a cage (confined-space) around the catalyst providing an ionic nano-container environment which serves as physical-chemical barrier that selectively controls the diffusion of reactants, intermediates, and products to the catalytic active sites via their hydrophobicity and contact ion pairs. Hence, the electronic properties of the catalysts in ILs can be tuned by the proper choice of the IL-cations and anions that strongly influence the residence time/diffusion of the reactants, intermediates, and products in the nano-environment. On the other hand, ILs provide driving force towards photocatalytic redox process to increase the CO₂ photoreduction. By combining ILs with the semiconductor, unique solid semiconductor-liquid commodities are generated that can lower the CO₂ activation energy barrier by modulating the electronic properties of the semiconductor surface. This mini-review provides a brief overview of the recent advances in IL assisted thermal conversion of CO₂ to hydrocarbons, formic acid, methanol, dimethyl carbonate, and cyclic carbonates as well as its photo-conversion to solar fuels.     

聚合物在咪唑类离子液体中的溶解

离子液体（ILs）具有难挥发、热稳定、宽液程和高电导率等独特优点,在聚合物领域中的应用受到越来越多的关注。由于ILs内部的复杂相互作用力,ILs的溶剂化能力还不能像分子溶剂那样有定量的方法来表征,特别是ILs与聚合物的相容性没有一个统一的判据。本文从咪唑基ILs内部的四个主要相互作用力出发,简述了ILs内部的相互作用对...     

Alternative sample-introduction technique to avoid breakthrough in gradient-elution liquid chromatography of polymers

Gradient-elution liquid chromatography (GELC) is a powerful tool for the characterization of synthetic polymers. However, gradient-elution chromatograms often suffer from breakthrough phenomena. Breakthrough can be averted by using a sample solvent as weak as the mobile phase. However, this approach is only applicable to polymers for which a sufficiently strong solvent exists which is at the same time a weak eluent. Finding such a solvent for a given polymer can be laborious or may even be impossible. Besides, when working with comprehensive two-dimensional LC the effluent of the first dimension is the injection solvent of the second dimension. In this case, it is not possible to avoid breakthrough by adjusting the eluent strength of the second-dimension injection solvent. Therefore, another strategy to avert breakthrough has to be implemented. In this work, we successfully avoided breakthrough in GELC by mixing the mobile phase not before, but after the autosampler. This was demonstrated measuring a blend of poly(methyl methacrylate) standards with different molecular-weights as model mixture with comprehensive two-dimensional GELC × size-exclusion chromatography. The strategy is thought to be applicable to all substances with a sufficiently strong dependence of retention on mobile-phase composition. This typically applies to large molecules (synthetic and natural polymers) and allows efficient refocusing. Unretained and barely retained substances are not refocused and therefore suffer in the proposed setup from peak broadening.     

Truce-Smiles Rearrangement of Diaryliodonium Salts in Ionic Liquids

The Truce-Smiles rearrangement is an intramolecular S_NAr reaction, enabling the formation of a new arene carbon-carbon bond with sufficiently strong carbon-centered nucleophile. Reported here are ortho-tosylmethylene functionalized diaryliodonium salts, which can undergo an unprecedented Truce-Smiles rearrangement in ionic liquids, resulting in sulfonyl-substituted ortho-iodo diarylmethanes as a powerful class of building blocks in chemical synthesis. The protocol features aryliodo moiety as a hyper nucleofuge, facilitating the formation of Meisenheimer complex within the migratory system.     

离子液体在制备金属氧化物纳米材料中的应用

总结了近年来在离子液体中制备金属氧化物纳米材料的新方法以及离子液体在金属氧化物纳米材料制备方面的应用及发展趋势.目前,对于制备纳米金属氧化物,离子液体主要是作为电解液、表面活性剂;其未来的发展趋势是离子热合成和集模板-溶剂-反应物于一身的离子液体反应.     

室温离子液体在色谱分离中的应用进展

室温离子液体作为21世纪的新型溶剂,近几年在分析领域应用广泛.本文重点综述了离子液体在气相色谱、液相色谱、毛细管电泳及薄层色谱等方面的应用进展,并对其在色谱分离中的研究进行了展望.     

Hierarchy of Order in Liquid Crystalline Polycaps

When outfitted with long alkyl chains , polycaps, capsules along a polymer chain, spontaneously organize themselves into a two-dimensional liquid crystalline phase. Further organization results from shearing or pulling the liquid crystalline samples, producing three-dimensional assemblies of micrometer-wide, infinitely long fibers (see schematic representation).     

壳聚糖基防粘连材料的构建及应用进展

术后粘连是影响手术效果甚至手术成败的关键问题之一,因此防止手术后粘连是一个亟待解决的问题。目前,人们已经开发出了多种防粘连材料。壳聚糖由于具有无毒性、无刺激性、无免疫抗原性、无热源性、不溶血、无致突变反应等优异性能,而被广泛用于包括防粘连材料在内的各种生物材料领域。本文结合本课题组在防粘连材料领域的研究,对各种类型壳聚糖基防粘连材料的研究现状及存在问题进行了综述,以期能够为设计和开发新型壳聚糖基防粘连材料提供重要参考。     

X-ray and neutron powder diffraction study of the order-disorder transition in Eu2IrH5 and the mixed crystal compounds Eu2−xAxIrH5 (A=Ca, Sr; x=1.0, 1.5)

The title compounds and their deuterides have been prepared by solid-state and solid-gas reactions from the elements and investigated by X-ray and neutron powder diffraction as a function of temperature. At room temperature they crystallize with an anion-deficient cubic K₂PtCl₆-type structure (space group ) in which five hydrogen (deuterium) atoms surround iridium randomly on six octahedral sites with average bond distances of Ir-D=169-171 pm. At low temperature they undergo a tetragonal deformation (space group I4/mmm) to the partially ordered Sr₂IrD₅ (T=4.2K)-type structure in which four hydrogen (deuterium) atoms occupy planar sites with full occupancy (Ir-D=166-170 pm) and two hydrogen (deuterium) atoms axial sites (Ir-D=174-181 pm) with ∼50% occupancy, i.e., the data are consistent with a mixture of square-pyramidal [IrD₅]⁴⁻ complexes pointing in two opposite directions. The transitions occur at ∼240 K (Eu_0.5Ca_1.5IrD₅, Eu_0.5Sr_1.5IrD₅), ∼210 K (EuSrIrD₅), ∼200 K (EuCaIrD₅, Eu₂IrD₅), and are presumably of first order.     

A data base for polymer chromatography: Temperature dependence of interaction parameters in liquid adsorption chromatography

The temperature dependence of retention behaviour of polyethylene glycol (PEG) and its mono‐ and dimethyl ethers was studied on various RP columns in different mobile phases. The accessible volumes and the interaction parameters were determined from slope and intercept in a plot of the elution volumes of the oligomers of a polymer homologous series as a function of the difference of the elution volumes of consecutive oligomers. A quite different dependence of the interaction parameters was observed in the different mobile phases. While in methanol–water the interaction parameter decreases with increasing temperature, the opposite effect is observed in acetonitrile (ACN)–water. In acetone–water, the temperature dependence is almost negligible.     

室温离子液体在分离分析中的应用

室温离子液体是指室温或接近室温下全部由离子组成的有机液体物质,具有不挥发,不易燃,溶解范围大,对空气和热稳定等特点,作为一种“可设计”型的环境相对友好溶剂,已被成功应用于分离分析领域中。本文重点综述了离子液体近年来在毛细管电泳、液相色谱及气相色谱中的应用进展,也对离子液体在质谱和光谱中的应用作了介绍。