The Synthesis of Cyclotriphosphazene Liquid Crystals

Generally,thermotropicliquidcrystalsareconstructedoforganiccomPoundsofanisotropicshaPe.Inthesearchfornewmoleculardesignsformesogensoforiginalshapes,onecanroughlyfollowtwodirections.Thefirstideaistovarythenumberofalkylchainsgraftedaroundagivencore.Thesecondideaofshapemodificationconsistsintheformationofclustersofafewidenticalmesogens,generallyatwin.Accordingtothesetwoideas,manynewkindsofliquidcrystalshavebeensysthesized.Hexakis(4-(4'-alkoxy)biphenoxy)cyclotriphosphazeneswerethemostinteresting…     

The Liquid Junction Potential in Potentiometric Titrations. XII. The Calculation of Potentials for Emf Cells with Liquid Junctions, of the Type, AY | AY + A2MoO4+HY, Involving the Formation of Iso-Polymolybdates in the Range ?log?10[H+]��7, at [A+]=C mol?L?1, Constant, and 25?��C

Equations are derived, in a general form, and valid in the range 0.5??C??3 mol?L^?1, for the calculation of the total potential anomalies (??E _H) for emf cells where the formation of iso-polymolybdates takes place, according to the equilibria: $$p \mathrm{H}^{+} (h) + q \mathrm{MoO}_{4}^{2 -} (b)\rightleftharpoons [(\mathrm{H}^{+})_{p}(\mathrm{MoO}_{4}^{2-})_{q} ] ^{p - 2q} (cpx _{pq})$$ by measuring [H⁺]=h, in NaClO₄ ionic medium (A⁺, Y^?) at [Na⁺]=3 mol?L^?1. The total cell emf (E _H), can be defined as: $$E_{\mathrm{H}} = E_{\mathrm{0H}} + g \log_{10} h + g\log_{10} f_{\mathrm{HTS}2} +E_{\mathrm{D}} + E_{\mathrm{D}f}$$ where: E _0H is an experimental constant, E _D+E _Df =E _J, the classical liquid junction potential, and glog?₁₀ f _JTS2+E _D+E _Df =??E _H. Here, $\mathrm{MoO}_{4}^{2 -}$ is the central ??metal ion??, E _D is the ideal diffusion potential (Hendersson equation), E _Df is the contribution of the activity coefficients to E _D. f _HTS2 denotes the activity coefficient of the H⁺ ions in the terminal solution TS2. The investigations of this system made by Sasaki and Sillén are critically analyzed. Some emf cells are supposed for the determination of the interaction coefficients involved. All calculations are valid at 25?°C. The revised equilibrium constants are presented in Table 14.     

BET Modeling of Solid–Liquid Phase Diagrams of Common Ion Binary Salt Hydrate Mixtures. I. The BET Parameters

Solid–liquid phase diagrams of binary salt hydrate mixtures can be modeled by means of the BET method, next paper, which considers the water as if it were adsorbed on sites of the salt. The parameter r describes the average number of sites and describes the molar enthalpy of adsorption in excess of the enthalpy of condensation of water vapor. The BET parameters r and required for the modeling were obtained for a large number of salts from water activities or related quantities of concentrated aqueous solutions of them. This paper consists of a comprehensive compilation of these two BET parameters for a large number of salts.     

The Effect of Alkane Chain Length on the Liquid–Liquid Critical Temperatures of Oligostyrene/Linear-Alkane Mixtures

Summary. Upper critical solution temperatures (UCSTs) for liquid–liquid demixing in a set of mixtures of linear alkanes (pentane (N ₁=5) to pentacontane (N ₁=50)) with an oligostyrene (1241amu, N ₂=12) are reported. We find strong correlation between the Hildebrand solubility parameters of the alkanes and the UCST. Correlations are developed which enable predictions concerning the miscibility of mixtures of compounds with longer chains.     

The Effect of Alkane Chain Length on the Liquid–Liquid Critical Temperatures of Oligostyrene/Linear-Alkane Mixtures

Upper critical solution temperatures (UCSTs) for liquid–liquid demixing in a set of mixtures of linear alkanes (pentane (N ₁=5) to pentacontane (N ₁=50)) with an oligostyrene (1241amu, N ₂=12) are reported. We find strong correlation between the Hildebrand solubility parameters of the alkanes and the UCST. Correlations are developed which enable predictions concerning the miscibility of mixtures of compounds with longer chains.     

Liquid–Liquid Equilibria of Some Aliphatic Alcohols + Disodium Hydrogen Citrate + Water Ternary Systems at 298.15 K

In this paper, the liquid?Cliquid equilibria for 1-propanol, 2-propanol or 2-methyl-2-propanol + disodium hydrogen citrate aqueous two-phase systems at 298.15 K were studied. The experimental binodal curves at 298.15?K are reported, and the parameters of the Merchuk equation, modified as a nonlinear function of mixed solvent properties and used for the simultaneous correlation of the experimental binodal data. Moreover, the salting-out ability of different salts and different alcohols with different anions is discussed. Additionally, experimental tie-line data are reported at 298.15 K. The generalized electrolyte-NRTL model of the mixed solvent electrolyte systems (e-NRTL) satisfactorily used for the correlation of the tie-line compositions; restricted binary interaction parameters were also obtained.     

Liquid–liquid phase equilibrium of methanol + ethylbenzene + isooctane + ethanol system at 303 K

The phase equilibrium data for methanol + ethanol + isooctane systems were obtained at 303.15 K. Data for methanol + ethylbenzene + isooctane system were taken from literature. The effect of ethanol addition on the system equilibrium was investigated at the same temperature. The distribution curves for ternary and quaternary system was analyzed. The experimental results for ternary systems were correlated with UNIQUAC and NRTL equations. For the ternary systems studied here, the NRTL equation is more accurate than the UNIQUAC. The equilibrium data for the three ternary systems were used to determine interactions parameters for the UNIQUAC equation. For the quaternary system, the experimental data can be fitted more accurately to UNIQUAC equation than by the UNIFAC method.     

BET Modeling of Solid–Liquid Phase Diagrams of Common-Ion Binary Salt Hydrate Mixtures. II. Calculation of Liquidus Temperatures

The BET method, according to which a molten salt hydrate is considered as if the water is adsorbed on sites of the salt, was used to model the liquidus temperatures of binary mixtures of common-ion salt hydrates. The method requires as input the BET parameters r, the number of sites and , the energy of adsorption in excess of that of the condensation of water vapor, as derived in the preceding paper. Further needed input information is the melting temperature of the salt that crystallizes out and its latent heat of melting. It is possible to model the liquidus temperature of the branch of the phase diagram between the pure salt that crystallizes out and the (first) eutectic encountered in the system with this input. The method was applied successfully to binary salt hydrate systems involving magnesium nitrate with magnesium acetate and with aluminum or nickel nitrates, magnesium and nickel chlorides, and calcium chloride with its bromide and nitrate, and with magnesium nitrate.     

Liquid Phase Isomerization of α-Pinene. Study of the Reaction on Sulfated ZrO2

The -pinene isomerization reaction was studied on sulfated zirconium oxide catalyst for different experimental conditions. The catalysts are active for producing camphene when they present Brönsted acidity and when zirconium oxide crystallizes in the tetragonal phase. The -pinene conversion and its selectivity to camphene can be optimised by proper selection of operating conditions such as temperature, catalyst concentration and reaction time. The use of this catalyst in the appropriate conditions can result in selectivity to camphene of about 70%.     

The Cloud Point Behaviors and the Liquid–Liquid Equilibrium of L31—Inorganic Sodium Salt Aqueous Two-Phase Systems

The cloud point (CP) of triblock-copolymer L31 aqueous solution was determined with salting-out salts (Na₂SO₄/Na₂CO₃/NaF/NaCl/NaBr). The results show that all these salts can decrease the CP of L31 aqueous solution and form aqueous two-phase system (ATPS). With increasing concentrations of Na₂SO₄ and Na₂CO₃, an obvious phase inversion could be observed and phase inversion points were found. This was mainly due to the change in density, the salt-rich phase shifted from the top phase to the bottom phase. Meanwhile, the liquid-liquid equilibrium (LLE) data for L31-Na₂SO₄/Na₂CO₃/NaF/NaCl/NaBr ATPSs were measured at 288.15 K. The salt ability to decrease the CP and to induce the phase separation is as follows: Na₂SO₄?>?Na₂CO₃, NaF?>?NaCl?>?NaBr. Finally, the order of anions that reduced the CP and caused phase separation was obtained as follows: SO₄^2? >CO₃^2?, F^??>?Cl^??>?Br^?.     

The rheological properties of gelatin gels containing κ-carrageenan. The role of polysaccharide

The influence of an anionic polysaccharide, κ-carrageenan, on the rheological properties of low-concentration (1.0 wt %) gelatin gels has been studied in a wide range of low polysaccharide concentrations (1 × 10^?3–5 × 10^?1 wt %) at a temperature of 14.0°C and pH values slightly higher than the isoelectric point of gelatin. The parameters characterizing the rheological properties of the gels are governed by the mass ratio between the polysaccharide and gelatin, which are able to form (bio)polyelectrolyte complexes in aqueous systems. There is a critical κ-carrageenan-to-gelatin mass ratio Z ? 0.1, above which the yield stress of the gels and their effective viscosit at stresses exceeding the yield point drastically rise. The increase in these rheological parameters correlates with a growth in the particle size of κ-carrageenan-gelatin polyelectrolyte complexes, which are formed in the aqueous bulk phase at an elevated temperature and precede gelation.     

Determination of Aristocularine Enantiomers by Dispersive Liquid–Liquid Microextraction and Chiral High-performance Liquid Chromatography

Here is reported a novel analytical approach for the extractive separation and determination of enantiomeric ratios of aristocularine in bovine serum albumin. The results demonstrate suitable analytical performances. The separation was performed by chiral high-performance liquid chromatography with a 5-µm column using a mobile phase of 1:1 n-hexane:ethanol at a flow rate of 0.7?mL?min^?1 with ultraviolet–visible absorption, circular dichroism, and polarimetric detection. The enantiomers were eluted at 13.2 and 15.6?min for (+) and (?)-aristocularine, with a resolution of 1.58 and a separation factor of 1.27. The analytical parameters for the dispersive liquid–liquid microextraction were optimized; under these conditions, the extraction recoveries were from 88.6% to 93.9% for a two-step extraction. The precision, reported as the percent relative standard deviation, had values from 2.9% to 3.2% for 0.5?µg?mL^?1 of analyte for five replicate measurements using ultraviolet–visible absorption and circular dichroism detection. The limits of detection were between 0.05 and 0.08?µg?mL^?1 with enrichment ratios up to a value of 12.     

The Huge World of Nanomaterials.From Wiley-VCH

~~The Huge World of Nanomaterials.From Wiley-VCH~~     

The Huge World of Nanomaterials. From Wiley-VCH

Nanoparticles From Theory to Application GNTHER SCHMID,Univ. Essen,Germany An introduction to the science of nanoparticles     

The Vast World of Nanomaterials. From Wiley-VCH

Nanotechnology MICHAEL KHLER,llmenau Technical Univ.,Inst. of Physics,llmenau,Germany,and WOLFGANG FRITZSCHE,IPHT Jena     

Liquid Chromatographic Determination of NSAIDs in Urine After Dispersive Liquid–Liquid Microextraction Based on Solidification of Floating Organic Droplets

An environmentally benign method of sample preparation based on dispersive liquid–liquid microextraction and solidification of floating organic droplets (DLLME-SFO) coupled with high-performance liquid chromatography with ultraviolet detection has been developed for analysis of non-steroidal anti-inflammatory drugs (NSAIDs) in biological fluids. A low-toxicity solvent was used to replace the chlorinated solvents commonly used in conventional DLLME. Seven conditions were investigated and optimized: type and volume of extraction solvent and dispersive solvent, extraction time, effect of addition of salt, and sample pH. Under the optimum conditions, good linearity was obtained in the range 0.01–10 µg mL⁻¹, with coefficients of determination (r ²) >0.9949. Detection limits were in the range 0.0034–0.0052 µg mL⁻¹ with good reproducibility (RSD) and satisfactory inter-day and intra-day recovery (95.7–115.6 %). The method was successfully used for analysis of diclofenac, mefenamic acid, and ketoprofen in human urine. Analysis of urine samples from a patient 2 and 4 h after administration of diclofenac revealed concentrations of 1.20 and 0.34 µg mL⁻¹, respectively.

     

The effect of styrene α-substituents on the regiochemistry of [2+2] cycloadditions with difluoroallene.

Consistent with our hypothesis for a mechanism involving two kinetically-distinct diradical intermediates, the observed effects of styrene α-substituents can be explained as deriving either from steric effects or radical stabilizing effects.     

The Ethylbenzene/Styrene Preferential Separation with Ionic Liquids in Liquid–Liquid Extraction

The objective of this work was to explore the feasibility of using ionic liquids (ILs), namely N-ethyl-N-methylmorpholinium dicyanamide, [EMMor][DCA], (3-hydroxypropyl)-1-methylmorpholinium dicyanamide, [N-C₃OHMMor][DCA], 1-(3-hydroxypropyl)-3-methylimidazolium dicyanamide, [N-C₃OHMIM][DCA], 1-(3-hydroxypropyl)pyridinium dicyanamide, [N-C₃OHPy][DCA], (3-cyanopropyl)pyridinium dicyanamide, [N-C₃CNPy][DCA], and (3-cyanopropyl)methylpyrrolidinium dicyanamide, [N-C₃CNMPyr][DCA] for the separation of ethylbenzene and styrene. The liquid–liquid equilibrium (LLE) data in ternary systems of {IL (1)?+?styrene (2)?+?ethylbenzene (3)} at T?=?298.15 K and ambient pressure is presented for the six ILs synthesized by us. The final chromatography analysis of the composition of tie-lines has shown that the studied ILs are not found in the raffinate phase and they show interesting results on the selectivity and solute distribution ratio for styrene extraction. A comparison of different ILs is presented for the studied separation problem. It was observed that the best separation selectivities were found for [N-C₃CNPy][DCA] (S_Av?=?2.38) and [N-C₃OHMMor][DCA] (S_Av?=?2.42) in comparison with other studied ILs in this work and those presented in the literature. While the data presented here are useful from a theoretical standpoint, the possibility of applications for these ILs in technological processes is questionable because of low solute distribution ratios, especially those calculated from the masses [N-C₃CNPy][DCA] (β_MAv?=?0.08) and [N-C₃OHMMor][DCA] (β_MAv?=?0.07). The experimental tie-lines were correlated with the non-random two liquid NRTL model.     

Dispersive Liquid–Liquid Microextraction for the Preconcentration of Multiple Classes of Pesticides in Water

A simple, rapid, efficient, and environmentally friendly method was developed for the preconcentration of atrazine, simazine, diuron, bentazone, tebuconazole, and fipronil from water. Dispersive liquid–liquid microextraction was employed with determination by liquid chromatography–tandem mass spectrometry. The volumes of extraction and disperser solvents, the concentration of sodium chloride, and the pH were optimized by response surface methodology. The optimum conditions involved the use of 150 µL of 1:1 (v/v) monochlorobenzene:dichlorobenzene as the extraction solvent, 2 mL acetonitrile as the disperser solvent, and 10 mL of sample at pH 3.0. The accuracy was evaluated in terms of recovery values that were from 54 to 112%. The relative standard deviations ranged from 4 to 27%. The limits of quantification were between 0.005 and 0.05 µg L^?1. The optimized method had low matrix effects for the analytes and the results demonstrated application for the determination of pesticides in water.