介孔氧化硅膜在多孔陶瓷载体上的组装

采用过滤成膜方式结合溶剂挥发诱导自组装方法在多孔氧化铝中空纤维上制备了介孔氧化硅膜。XRD、TEM和N₂吸附脱附实验结果显示非担载膜具有有序的六方介孔结构。通过对中空纤维担载膜的XRD分析进一步确认介孔氧化硅膜的形成。SEM和EDS线扫描结果显示制备的担载膜表面完整、无缺陷,膜层和载体界面之间结合紧密。在此基础上对介孔膜在多孔陶瓷载体上的形成机理进行了探讨。     

Rheological Properties of Aqueous H-Carboxymethyl Cellulose Solutions with Various Additives

Rheological properties of moderately concentrated aqueous solutions of carboxymethyl cellulose in the H form with various additives were studied.     

Phase Behavior and Rheological Properties of Concentrated Lecithin Aqueous Solutions with Additives

The phase behavior and rheological properties of the concentrated lecithin aqueous solutions were investigated at 37°C. When adding Isopropyl myristate (IPM) to lecithin solutions, besides an anisotropic liquid crystal (LC) phase, an isotropic liquid (L₂) region and an isotropic viscous (I) phase are found. By continuously adding Brij 97, the LC region shifts towards higher water content and the L₂ region is extended to the area of lower IPM concentration, meanwhile the I phase disappears. By analyzing the shear rate (η_γ=0.1) and yield stress (σ₀), adding IPM to lecithin solutions increases the values of η_γ=0.1 and σ₀, and after further adding Brij 97, the η_γ=0.1 and σ₀ decrease dramatically. Notably, different from the lecithin/DDAB/water system studied by Youssry and Montalvo, in lecithin/Brij 97/IPM/H₂O system, at the relatively higher water content area of the LC phase, the water content has little effect on the critical stress. It is also found that the change of dynamic storage modulus (G′) is similar with that of η_γ=0.1 and σ₀ parameters when adding IPM and Brij 97. Maxwell model fitting results show that in the LC phase, the relaxation of the water molecule is prolonged by adding IPM and Brij 97 to lecithin solutions.     

Layer Buildup on Two-Layered Porous Substrate by Dip-Coating: Modeling and Effect of Additives on Growth Rate

A model was developed to describe layer buildup on a two-layered substrate during dip-coating. In this model, the growth rate can be used to estimate the permeability of the cast layer. Layers of submicron alumina were dip-coated onto the asymmetric porous substrate to evaluate the model. The layer buildup and properties were studied with different slip additives. Slips were deflocculated with nitric acid or sodium poly(methacrylic acid) (Na-PMAA) to achieve electrostatic or electrosteric stabilization. Properties of the slips with electrostatic stabilization were varied with poly(vinyl alcohol) (PVA) concentration. Properties of the slips with electrosteric stabilization were varied with Na-PMAA concentration. PVA addition decreased the growth rate of the layer by reducing capillary pressure and increasing the viscosity of the filtrate. Electrostatic stabilization of the slip with PVA addition also led to almost complete deflocculation and a rather high density of layers. Na-PMAA addition led to fast growth of the layer. Na-PMAA addition increased the capillary pressure and had a minor effect on the viscosity of the liquid phase. Na-PMAA addition led to an incomplete dispersion of particles and therefore a high porosity of layers. Permeability values of coated layers obtained from the model were compared with permeability values predicted by the Kozeny-Carman equation. In the case of complete deflocculation of the slip, the permeability values estimated with the model correlated reasonably well with the predicted values. Incomplete deflocculation led to higher permeability values than predicted by the Kozeny-Carman equation. Copyright 2000 Academic Press.     

Hydrophobization of Porous Ceramic Materials Based on Quartz Fibers with Solutions of Tetrafluoroethylene Telomers

Russian Journal of Applied Chemistry - Hydrophobization of highly porous heat-shielding ceramic materials based on quartz fibers was studied. Radiation-synthesized tetrafluoroethylene telomers...     

Enthalpies of Absorption and Solubility of Carbon Dioxide in Aqueous Polyamine Solutions

The enthalpies of absorption and solubility at T=298.15 K of carbon dioxide in aqueous solutions of bis-(3-dimethylaminopropyl)amine (CAS RN: [6711-48-4]) are reported in this paper. It was observed that the saturation loading of the CO₂ is α=2.9 mol CO₂/mol TMBPA, which is close to the theoretical value, α⁰=3 mol CO₂/mol TMBPA. The molar heat of absorption of CO₂ is independent of the polyamine concentration of the solutions and the amount of CO₂ absorbed and was calculated to be Δ_abs H _m=–44 (±2) kJ mol^–1 CO₂. This revised version was published online in July 2006 with corrections to the Cover Date.     

底物,水量对脂肪酶不对称拆分萘普生的影响

选择了一种便于底物－产物分离的微水－有机两相体系,将对Ｓ－（＋＿萘普生酯有高度对映体选择性的ＣＣＬ脂肪酶固定于硅藻土上。合成了了一种能提高酶催化反应速度的激活的酯－萘普生氯乙酯。     

Vibronic Structures in Absorption and Fluorescence Spectra of Firefly Oxyluciferin in Aqueous Solutions

To elucidate the factors determining the spectral shapes and widths of the absorption and fluorescence spectra for keto and enol oxyluciferin and their conjugate bases in aqueous solutions, the intensities of vibronic transitions between their ground and first electronic excited states were calculated for the first time via estimation of the vibrational Franck–Condon factors. The major normal modes, overtones and combination tones in absorption and fluorescence spectra are similar for all species. The theoretical full widths at half maximum of absorption spectra are 0.4–0.7 eV and those for the fluorescence spectra are 0.4–0.5 eV, except for phenolate‐keto that exhibits exceptionally sharp peak widths due to the dominance of the 0–0′ or 0′–0 band. These spectral shapes and widths explain many relevant features of the experimentally observed spectra.     

Partial Molal Volumes of Asymmetric Iodides of Butyl-Triethyl-Ammonium in Aqueous Solutions at 298,15 K

Abstract

Density measurements have been made on aqueous solutions of t-BuEt₃NI, s-BuEt₃NI, i-BuEt₃NI, Bu₄NI and Et₄NI at 298,15 K from 0,01 to 0,05 m. The apparent molal volumes V0₂ calculated from the V _2,? (m) plots for the salts show a decrease value: n-BuEt₃NI > i-BuEt₃NI > s-BuEt₃NI > t-BuEt₃NI. The data analysis may suggest that the cations with the butyl isomers perform two groups: n-BuEt₃N⁺ and i-BuEt₃N⁺ with the highest V ₂ ⁰, and t-BuEt₃N⁺ and s-BuEt₃N⁺ similar to Et₄N⁺ one. The peculiarities of the experimental observation may be interpreted as a consequence of the structural effect over the intermolecular forces that affect the solute-water interactions deeply.     

Possibility of Producing Semisolid Dosage Forms Based on Aqueous Solutions of Chitosan Succinamide in the Presence of Modification Additives

Russian Journal of Applied Chemistry - The rheological behavior of the water-soluble chitosan derivative chitosan succinamide in a solvent—modifying additive system (ethanol, ethylene glycol,...     

A Porous Ceramic Based on Aluminomagnesium Spinel

Powdered precursors of an aluminomagnesium spinel were synthesized by joint crystallization of magnesium and aluminum salts from solutions. The sequence of stages of the MgAl₂O₄ formation was studied in relation to the nature of initial reagents and temperature of heat treatment. Optimal modes of sintering of the aluminomagnesium spinel for obtaining ceramic materials with porosity greater than 50% were determined.     

新型芳香三嗪超交联多孔聚合物去除水溶液中甲基橙

Organic dyes, especially the harmful cationic dye methyl orange (MO), are emerging pollutants. The development of new materials for their efficient adsorption and removal is thus of great significance. Porous organic polymers (POPs) such as hyper-cross-linked polymers, covalent organic frameworks, conjugated microporous polymers, and polymers with intrinsic microporosity are a new class of materials constructed from organic molecular building blocks. To design POPs both with good porosity and task-specific functionalization is still a critical challenge. In this study, we have demonstrated a simple one-step method for the synthesis of the hyper-cross-linked aromatic triazine porous polymer (HAPP) via the Friedel-Crafts reaction. The resultant porous polymer was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, elemental analysis (EA), thermo-gravimetric analysis (TGA), solid-state ¹³C nuclear magnetic resonance (¹³C NMR), and nitrogen adsorption-desorption isotherms. The results show that HAPP is a rough, irregular morphology, porous organic polymer that is amorphous in nature. The novel polymer showed high Brunauer-Emmett-Teller surface area (of up to 104.36 m²∙g⁻¹), porosity, and physicochemical stability. Owing to the presence of N heteroatom pore surfaces in the network, the material exhibited a maximum adsorption capacity of 249.3 mg∙g⁻¹ for MO from aqueous solutions at room temperature. This is higher than that of some reported porous materials under the same conditions. To explain this phenomenon more clearly, theoretical quantum calculations were performed via the DFT method using Gaussian 09 software and Multiwfn version 3.4.1. It is performed to analyze the properties and electrostatic potential (ESP) of the HAPP monomer and MO. The results indicated that the N heteroatom of HAPP can easily develop strong interactions with MO, supporting the efficient adsorption of MO. The parameters studied include the physical and chemical properties of adsorption, pH, contact time, and initial concentrations. The percentage of MO removal increased as the pH was increased from 2 to 4. The optimum pH required for maximum adsorption was found to be 5.6. Adsorption kinetics data were modeled using the pseudo-first-order and pseudo-second-order models. The results indicate that the second-order model best describes the kinetic adsorption data. The adsorption isotherms revealed a good fit with the Langmuir model. More importantly, the HAPP can be regenerated effectively and recycled at least five times without significant loss of adsorption capacity. Therefore, it is believed that HAPPs with hierarchical porous structures, high surface areas, and physicochemical stability are promising candidates for the purification and treatment of dyes in solution.     

脂肪胺水溶液吸收CO2的热力学参数的密度泛函理论研究

采用密度泛函理论研究CO2在脂肪胺水溶液热力学参数．研究的脂肪胺包括烷基胺、链烷醇胺、二胺以及氨基酰胺．在B3LYP/6-311＋ G（d,p）水平计算脂肪胺在CO2气相中的振动频率．通过连续介质模型在HF/6-31G（d）水平计算了溶剂几何优化的标准自由能,评价了CO2吸收到脂肪胺水溶液过程有关的两个重要参数：酸解离常数和标准焓变二者之间大致呈线性关系．随着胺碱度的提高,CO2吸收过程释放的热量增加,则胺再生所需的能量增加．     

光谱法研究尿素对水溶液中血红蛋白构象的影响

应用荧光猝灭法和动态光散射法测定尿素-水混合溶剂中血红蛋白(Hb)与联苯胺的结合距离和Hb的流体动力学半径. 结合Hb的荧光光谱和吸收光谱, 探讨尿素与蛋白质分子在水溶液中相互作用的机理及其对蛋白质构象的影响. 结果显示, 尿素分子取代水分子在蛋白质周围形成溶剂化层, 并与骨架肽链和亲水侧链形成氢键, 从而积聚在蛋白质分子表面. 尿素分子与蛋白质分子之间的直接相互作用对蛋白质的构象具有复杂的影响, 高浓度的尿素-水混合溶剂破坏蛋白质的构象, 而低浓度的混合溶剂则有利于蛋白质形成更紧密的构象. 在高浓度的尿素-水混合溶剂中, Hb血红素疏水空穴失去原有的三级结构后形成一个与熔球态相类似的结构.     

Theoretical Study of Firefly Luciferin pKa Values—Relative Absorption Intensity in Aqueous Solutions

Ground‐state vibrational analyses of firefly luciferin and its conjugate acids and bases are performed. The Gibbs free energies obtained from these analyses are used to estimate pK_a values for phenolic hydroxy and carboxy groups and the N–H⁺ bond in the N‐protonated thiazoline or benzothiazole ring of firefly luciferin. The theoretical pK_a values are corrected using the experimental values. The concentrations of these chemical species in solutions with different pH values are estimated from their corrected pK_a values, and the pH dependence of their relative absorption intensities is elucidated. With the results obtained we assign the experimental spectra unequivocally. Especially, the small peak near 400 nm at pH 1–2 in experimental absorption spectra is clarified to be due to the excitation of carboxylate anion with N‐protonated thiazoline ring of firefly luciferin. Our results show that the pK_a values of chemical species, which are contained in the aqueous solutions, are effective to assign experimental absorption spectra.     

Quantitative Determination of Cationic and Nonionic Surfactants in Aqueous Solutions of Their Mixtures by Capillary Zone Electrophoresis

A method based on capillary zone electrophoresis is developed for a quantitative determination of cationic (dodecylpyridinium bromide) and nonionic (Triton X-100) surfactants absorbing in the UV region. The effect of the pH and ionic strength of the solution on the output time and shape of the resultant peaks is studied, and the optimal conditions of the analysis are determined. For both surfactants, the analytical signal (the area of the peak on the electrophoregram) is found to linearly depend on the concentration. It is established that the presence of a second surface-active component does not affect the signal of the surfactant analyzed; thus, surfactants may be quantitatively determined in both individual and mixed solutions. The method of capillary zone electrophoresis is shown to be applicable for determining the CMCs of surfactants.     

助剂对L-脯氨酸催化直接不对称Aldol反应的影响

在L-脯氨酸催化的芳香醛与丙酮直接不对称aldol反应体系中添加二醇或二酚类助剂可有效提高反应活性.助剂的使用降低了该反应体系中L-脯氨酸的用量.特别是以邻苯二酚为助剂时,最佳反应条件下,仅用5mol％L-脯氨酸与1mol％助剂催化2-硝基苯甲醛与丙酮直接不对称aldol反应,aldol产物产率高达90％,对映选择性为...     

Study on the Absorption Properties of C_(60) in Micellar Aqueous Solutions and Mechanisms for Solubilisation

SincethesuccessfijlpreparationandmasssynthesisofC,,.tremendousinterestshavebeenevokedinitsunusualfull-carbonstructurelikefootballandphysicalandchemicalproperties,whichhavebeenstudiedcarefullyandsystematically.However,suchworksaremainlycarriedoutinorganicsolvents,especiallyinarenesolvents(benzeneortoluene),duetothewater-insolublenatureofC,o'In1992,Andersonetal.'firstobtainedthewater-solubleC,,successfullyviacyclodextrin(CD)enclosing,soastoopenanewwayforstudyingofC,,inaqueoussolutions.Afterth…     

Deconvolution of Complex Absorption Spectra Recorded in the Pulse Radiolysis of Aqueous Solutions of 3,5-Dihydroxytolyene

The optical absorption spectra of short-lived species generated in aerated aqueous solutions of 3,5-dihydroxytoluene, a representative of alkylhydroxybenzenes, by the action of single electron beam pulses were recorded. The decay curves recorded at different wavelengths differ from each other, thus suggesting that the transient species react with one another and with water via a complex mechanism and making it possible to discriminate between individual bands characterizing each particular species in the overall spectrum. Two procedures for analyzing complex absorption spectra were employed: (i) with the use of spectra observed at different time delays after the electron pulse and (ii) with deconvolution into a sum of Gaussians.     

Migration of Additives from Poly(vinyl chloride) (PVC) Tubes into Aqueous Media

The stability and migration product of medical PVC tubes plasticized with polyadipates were investigated by ageing in phosphate buffer at pH 1.679 and water at different temperatures. Changes in the PVC tubes were studied by water absorption, weight loss, Fourier infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The low molecular weight migration product that was released was extracted and silylanized before gas chromatography/mass spectroscopy (GC/MS) identification and quantification. After 70 days, the weight loss was less than 0.5% and only a small amount of adipic acid migrated when a tube was aged at 37°C in water and phosphate buffer (pH 1.679), and at 70°C in water after 56 days. However, when aged at 70 and 110°C, gradual deactivation of heat stabilizer after 21 days of ageing in buffer solution and separation of plasticizer from PVC matrix occurred. When the tube was aged at 110°C, significant degradation of both polyadipates and PVC were observed. Adipic acid and 1,4-butanediol monomers and oligomers of polyadipate were the major migration products from polyadipates in the water ageing solution, while only a relatively high amount of adipic acid was identified as the main product in the buffer ageing solution.