Stabilization of Water‐Soluble Antioxidant in Water‐in‐Oil‐in‐Water Double Emulsions

Abstract

In this study, we are introducing a method that can effectively stabilize antioxidants in water‐in‐oil‐in‐water (W/O/W) double emulsions. Preliminarily, stable W/O/W double emulsions were produced by manipulating the characteristics of internal aqueous phase via two‐stage emulsification, resulting consequently in the formation of fine internal water droplets in the dispersed oil droplets. From conductivity measurements that can determine the elution amount of internal aqueous phase, it was confirmed that the double emulsion stability could be improved by treating the internal aqueous phase with a hydroxypropyl‐beta‐cyclodextrin. In this study, kojic acid, 5‐hydroxy‐2‐(hydroxymethyl)‐4‐pyrone was selected as a model antioxidant. The stabilization of kojic acid was attempted by locating it in the internal water droplets of the stable W/O/W double emulsions. The stability of kojic acid in the double emulsion system could be maintained at 90% for 10 weeks at high temperature. We believe that these stable W/O/W double emulsions could be used meaningfully as a carrier for many unstable antioxidants.     

Cryoscopic Studies of the Uranyl Sulfate–Water, Uranyl Nitrate–Water, and Uranyl Nitrate–Nitric Acid–Water Systems

Freezing point lowerings of aqueous solutions of uranyl sulfate in the concentration range m 0.40 mol-kg^–1 and the activity and osmotic coefficients, which were calculated using the Pitzer equations for 2:2 electrolytes, are presented. Crystallization temperatures are reported for 0 to 13 molar nitric acid and 10–150 g uranium per liter uranyl nitrate–nitric acid–water solutions.     

Is Water Templating Nanoporous Materials?

(H(2)O)(17), a cluster with pentagonal water arrangements, squeezed in the sodalite cage of the crystal structure MIL-74 (Zn(6)Al(12)P(24)O(96).[N(CH(2)CH(2)NH(3))(3)](8).(H(2)O)(34)), has its oxygen atoms well located by X-ray powder diffraction. Positioning of hydrogen atoms has been performed by a dynamic partial atomic charges and hardnesses analysis calculation, in which partial charges are recalculated for each hydrogen sub-network modification. Hydrogen atoms are therefore positioned by energy minimization. A quantitative estimation of the hydrogen bonds energy for each H-bond and for the network in the MIL-74 nanoporous compound has been obtained. This result allows a discussion of the effect of imprinting the nanoporous structure onto water or alternatively the templating effect of the cluster onto the inorganic framework.     

First Magnesium-mediated Carbonyl Benzylation in Water

Catalyzed by AgNO3, Mg was found for the first time to be able to mediate the coupling reaction between aromatic aldehydes and benzyl bromide or chloride in water. The yields were slightly higher than the recent results for Mg-mediated allylation despite the fact that aqueous benzylation is intrinsically much harder than allylation. It was also found that the coupling reaction was chemoselective for aromatic aldehydes over aliphatic aldehydes, and chemoselective for aromatic aldehydes over aromatic ketones.     

Paal–Knorr Pyrrole Synthesis in Water

Water was a suitable medium for Paal–Knorr pyrrole cyclocondensation. Hexa-2,5-dione was reacted with several aliphatic and aromatic primary amines, affording N-substituted 2,5-dimethyl pyrrole derivatives in good to excellent yields. An efficient, green method using water either as environmentally friendly solvent or catalyst was presented.     

Dielectric Relaxation in Glycine–Water and Glycine–Ethanol–Water Solutions Using Time Domain Reflectometry

Dielectric relaxation measurements on water–ethanol–glycine ternary system were carried out using time domain reflectometry (TDR) at 25, 30, 35, and 40°C in the frequency range from 10 MHz to 10 GHz. Glycine–ethanol–water solutions are prepared with different concentrations of ethanol (0, 5, 10, 15, 20, and 30%) and also for different glycine molar concentrations (0, 0.2, 0.4, 0.6, 0.8, and 1 M). The dielectric relaxation parameters are measured for aqueous glycine solutions also to compare the results with those for the glycine–ethanol–water ternary system. For all the mixtures considered, only one relaxation peak was observed in this frequency range. All the mixtures display a Cole–Davidson dispersion. The relaxation peaks shift to lower frequency with an increase in glycine concentration and also with ethanol concentration. The logarithm of the relaxation time log() shows a nonlinear relation with glycine concentration which implies a change of relaxation mechanism with glycine concentration. The dielectric strength for these mixtures shows a nearly linear relation with glycine molar concentration.     

Liquid–Solid Phase Diagrams of PrOH–Water and BuOH–Water Systems from Differential Scanning Calorimetry

The freezing process in i-PrOH- and tert-BuOH-water systems were investigatedto obtain reliable liquid=nsolid phase diagrams by differential scanning calorimetry(DSC), especially focusing on formation of metastable solid phases. In addition,n-BuOH, sec-BuOH, and i-BuOH were studied within their solubility limits. Inmost systems studied, there exist metastable solid phases and, with increasingbranching of alkyl groups, the number of metstable solid phases increases. Themost complicated is i-PrOH-water where curious phenomena were found,probably because of the abnormally high viscosity of the solution at low temperatures.The relation between hydration in the liquid and formation of solid phases isdiscussed. It is suggested that the positional relation between methyl groups andalcoholic OH groups plays an important role; the increase in number ofalphamethyl group seems to strengthen hydration and stabilizes solid hydrates.     

Equations for the Partition of Neutral Molecules, Ions and Ionic Species from Water to Water–Ethanol Mixtures

Equations set up for the transfer of neutral solutes from water to water?Cethanol mixtures can also be used to correlate the transfer of ions and ionic species, as log₁₀ P, where P is the partition coefficient. Only two additional terms are required in the equations, one for anions and one for cations. The extended equations can fit log₁₀ P values for anions and cations with a standard deviation of about 0.2 to 0.3 log units for transfer of 41 anions and cations from water to various water?Cethanol mixtures from 10?% ethanol to 100?% ethanol by volume. The log₁₀ P values for carboxylate anions and protonated amine cations as obtained from the variation of pK _a with solvent are quite compatible with log₁₀ P values for simple anions and cations.     

Heck Reaction Catalyzed by Palladacycle in Neat Water

Cydopalladated ferrocenylimine has been found to be a type of excellent phosphine-free catalyst for Heck reactions in neat water with both higher yields and turnover numbers than those reported in the literature up to now. Some commercial emulsifying agents, indodin~ the commonly used quaternary ammonium salts, have been proved to be excellent additives in the catalysis of the reactions. Not only aromatic iodide, but also aromatic bromide could be coupled with the olef‘ms. All rcactions were able to be conducted in air under refluxlng condition.     

Microwave-promoted Palladium Catalyzed Suzuki Cross-coupling Reaction in Water

Suzuki coupling is probably the most versatile approach among the cross-coupling reactions and the reaction has long been the subject of intensive work in the area of transition-metal chemistry1. In recent years, various modifications involving the catalyst, solvents, bases, reaction conditions and synthetic technique have been developed 2. The Suzuki cross-coupling reaction in water is more safe, economical. It is an environmentally friendly alternative in organic synthesis. The use of w…     

Water’s surface tension and cavity thermodynamics

The relationship between cavity thermodynamics in water and air-water surface tension is investigated in the present study. The effective hard sphere diameter of water molecules over a large temperature range is estimated from the experimental air-water surface tension, and cavity thermodynamics is calculated by means of classic scaled particle theory. The work of cavity creation proves to be a decreasing function of temperature and the cavity entropy change is a positive, practically constant, quantity, regardless of the cavity diameter, in marked contrast with well established theoretical and computer simulation results. This finding suggests that the relationship between cavity thermodynamics and surface tension is not a simple matter in the case of water.     

A Novel Zn(Ⅱ)Complex with 1D Supramolecular Water Tape Formed by Cyclic Tetrameric Water Clusters

<正>A new mixed-ligand Zn(Ⅱ)complex,[Zn(4,4'-bipy)_2(H_2O)_4]·2ANS·6H_2O(1,4,4'- bipy=4,4'-bipyridine,HANS=2-aminonaphthalene-1-sulfonic acid),has been isolated and structurally characterized by single-crystal X-ray diffraction,FT-IR spectrum,TG and elemental analysis.It crystallizes in the monoclinic system,space group P2_l/c with a=12.4852(8),b= 18.3163(12),c=10.9707(7)(?),β=114.2600(10)°,V=2287.3(3)(?)~3,D_c=1.455 g/cm~3,M_r= 1002.37,Z=2,F(000)=1048,μ=0.704 mm~(-1),the final R=0.0408 and wR=0.962 for 4029 observed reflections with I2σ(I).Interestingly,an unusual one-dimensional(1D)water tape with cyclic tetrameric water clusters can be observed in 1,which are further trapped via Zn-O coordination bonds exhibiting a 2D Zn(Ⅱ)-water layer.These 2D Zn(Ⅱ)-water layers are stacked together into a 3D interdigitated supramolecular architecture via weakπ…πinteractions,in which free ANS anions are tightly filled by hydrogen-bonding interactions.Thus,π…πand classical hydrogen-bonding interactions are found as main driving forces to stabilize the 2D Zn(Ⅱ)-water layers.     

Molecular Simulation on Transport Properties of Confined Water

The diffusivity and viscosity of water confined in micropores were studied by molecular dynamics simulations. The effects of pore width and density were analyzed at pore widths from 0.9 to 2.6nm. The diffusivity in micropores is lower than that of the bulk, and it decreases as pore width decreases and as density increases. But the viscosity in micropores is much larger than that of the bulk, and it increases as pore width decreases and as density increases. The diffusivity in channel parallel direction is obviously larger than that in channel perpendicular directions.     

How Much Water Does Calcined Gypsum Contain?

Ordered water : Gypsum has been used for construction for millennia. The structure and water content of calcined gypsum, CaSO₄?0.5 H₂O, has been under discussion until now: single‐crystal structure analysis (see picture: S yellow, Ca gray, O blue, H red) provides an ordered model that is confirmed by DFT calculations.

     

Water absorbancy of never‐dried cotton fibers

Although neverdried cotton (NDC) fiber has been known to exhibit extremely high water absorbency, the reason for this has not yet been elucidated. In this study, changes in water absorbency, bound water content as revealed by differential scanning calorimetry (DSC), cellulose content and fiber crosssection observed by scanning electron microscopy (SEM) for NDC fibers at several stages of development (27–57 days postanthesis (DPA)) were investigated. It was found that the bound water content (27g/l00g) of NDC fibers at 50DPA is much smaller than that (40–73g/l00g) for fibers at 27–43DPA. Cellulose synthesis takes place within the cotton boll, a closed watercontaining system. Our results are rationalized by assuming that these water molecules are preventing the formation of intermolecular hydrogen bonds between the cellulose molecules as they are being formed. Other explanations for our experimental findings are: (i) the coexistence of precursors of cellulose and components, such as (1,3);glucans, that are very hydrophilic, and (ii) the presence in each NDC fiber of a prominent lumen that acts as a capillary system for water.     

Water–Electrolyte Glass-Forming Systems: A Review

Water–electrolyte systems comprising aqueous solutions of nitrates, iodates, sulfates, acetates, orthophosphates, chlorides, and fluorides of Group I–III metals, transition metals, and lanthanides were studied. Studies of glass formation in the system Al₂(SO₄)₃–H₂O serve as an example to give an idea of the original method for studying water–electrolyte glass-forming solutions and glasses developed at the Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, enabling one to predict their structures. This investigation method and analysis of experimental data have no analogues either in Russia or abroad. The results obtained were used to elucidate general glass formation trends in various water–electrolyte systems. We were the first to prove a polymeric structure of glass-forming compositions in some water–electrolyte systems. We were also the first to combine the glasses of water–electrolyte systems in a special class of glasses that are hydrogen-bonded polymeric items.