Water Solubilization in Mixed Nonionic Surfactants Microemulsions

The systems investigated were water/sucrose laurate/ethoxylated mono-di-glyceride/oleic phase. The oleic phase used first was the pure oils R (+)-limonene, isopropylmyristate, and caprylic-capric triglyceride; these oils were then mixed with ethanol at different mixing ratios (w/w). The total area of the one phase microemulsion region is dependent on the mixing ratios (w/w) of the mixed surfactants and that of the ethanol/oil. The largest microemulsion phase area formed with a surfactants mixing ratio (w/w) equals unity. For the systems where the oleic phase was a mixture of oil and ethanol, the total area of the monophasic microemulsion increases with the increase in the ethanol/oil mixing ratio (w/w). The Gibbs free energy of solubilization was estimated. It increases as the mixing ratio (w/w) of ethoxylated mono-di-glyceride/sucrose laurate increases and with the increase in the ethanol/oil mixing ratio (w/w). The Gibbs free energy of solubilization decreases with the increase in the water content in the water-in-oil microemulsions. The values of the Gibbs free energy of solubilization are higher for oil-in-water microemulsions compared to those of the water-in-oil microemulsions.     

Solubilization of Celecoxib in Microemulsions Based on Mixed Nonionic Surfactants and Peppermint Oil

U-type microemulsions formulated with water, mixed nonionic surfactants, and peppermint oil were used to solubilize celecoxib. Microemulsion dilution and interfacial factors contributing to the celecoxib solubilization were evaluated. Celecoxib solubilization capacity decreases with the increase in the water content. Electrical conductivity, dynamic viscosity, and SAXS measurements reveal the structural transition occurring in the microemulsion region. It was found that below 0.25 aqueous phase volume fraction the water-in-oil microemulsions are present, the transition between the water-in-oil to bicontinuous and then to oil-in water microemulsions occur at 0.30 and 0.8 aqueous phase volume fraction, respectively. The results demonstrate that the solubilized drug affects the transition from bicontinuous to water-in-oil microemulsions. The solubilized drug increases the hydrodynamic radius of the oil-in-water microemulsion droplets measured by dynamic light scattering.     

Diclofenac Solubilization in Microemulsions Based on Mixed Nonionic Surfactants and R (+)-limonene

Diclofenac is a nonsteroidal anti-inflammatory drug that reduces inflammation and pain hormones in the body. Dispersing the drug in water is impossible and its solubility in oils is very limited. In this study, we solubilized sodium diclofenac in nanostructures of the constructed U-type water/sucrose laurate/ethoxylated mono-di-glyceride/oleic phase microemulsions. The mixing ratio (w/w) of sucrose laurate/ethoxylated mono-di-glyceride equals unity. The oleic phase was the pure R (+)-limonene or R (+)-limonene mixed with ethanol at a weight ratio equals unity. The solubilization capacity of the drug in these systems is many times higher than in either oil or water systems. The sodium diclofenac solubilized microemulsions are fully diluted with water without phase separation. The solubilization capacity decreases as the water content increases. The system free of alcohol solubilizes less amounts of drug over all the range of water contents compared to the system containing alcohol. Small angle x-ray scattering was used to evaluate the effect of solubilized sodium diclofenac on the microstructure and diffusion properties of the loaded microemulsions. From the periodicity and correlation length measured by small angle x-ray scattering, we learned that the drug affects the structure of loaded microemulsion droplets probably less spherical than the empty systems. The transition from water-in-oil to a bicontinuous phase occurs at the different water contents compared to the empty (i.e., without drug) microemulsions. The drug remains solubilized at the interface upon further dilution with water and is oriented with its hydrophilic part facing the water, and strongly affects the inversion to oil-in-water droplets.     

Solubilization Enhancing Effect of A-B-Type Silicone Surfactants in Microemulsions

We report a solubilization enhancing effect of A-B-type silicone surfactants in microemulsions. The effect of added long-chain silicone surfactants, Si₂₅C₃EO_51.6 (extended length≈21.8 nm) and Si₁₄C₃EO_15.8 (extended length≈8.5 nm) on the solubilization capacity of C₁₂EO₅ (extended length≈3 nm)/water/dodecane microemulsion was investigated at the hydrophile-lipophile balance temperature at which a microemulsion (surfactant) phase containing equal weights of oil and water touches the three-phase body. The addition of silicone surfactants exhibits an enormous increase of the swelling of the middle phase primarily with an associated increase in the structural length scale of the microemulsion. The solubilization power increases with increasing x₂ (mole fraction of silicone surfactants to the total surfactant) and going through a maximum it decreases, since a lamellar liquid crystal introduces in the multiphase region at low surfactant concentrations. The solubilization capacity reaches at the maximum to an almost equal level for different x₂ values, 0.02 for Si₂₅C₃EO_51.6 and 0.09 for Si₁₄C₃EO_15.8. The solubilization power of the lamellar phase shows a similar trend with lower magnitude.     

Structural Parameters of Mixed Nonionic Surfactants Microemulsions

In this study, we estimated the structural parameters of water/mixed nonionic surfactants/R (+)-limonene microemulsions. The mixed surfactants are sucrose laurate and ethoxylated mono-di-glyceride. U-type microemulsion region was observed in these systems. It was found that changes in the surfactants mixing ratio, surfactants contents and oil/water weight ratio in the microemulsions incite a considerable change in the aggregation number, core radius and interfacial area per mixed surfactants head groups in the formed microemulsions. The interfacial area per mixed surfactant head groups increases while the aggregation number decreases with the increase in the ethoxylated mono-di-glyceride mass fraction in the mixed surfactants. The For an oil/water weight content equals unity, the interfacial area per mixed surfactants head groups is constant for mixed surfactants contents below 35 wt%. For mixed surfactants contents above 35 wt% the interfacial area per mixed surfactants head groups decrease and stabilizes at the lower value. The aggregation number decreases with the increase in the mixed surfactants contents. The aggregation number decreases also with the increase in the oil/water weight ratio at fixed mixed surfactants content.     

Conductive Flow Parameters of Mixed Nonionic Surfactants Microemulsions

This article focuses on the electrical conductivity study of the brine solution/sucrose laurate/ethoxylated mono-di-glyceride/oil + ethanol system. The oils were R (+)-limonene, isopropylmyristate and caprylic-capric triglyceride. The mixing ratio (w/w) of ethanol/oil and that of sucrose laurate/ethoxylated mono-di-glyceride equal unity. The brine solution was 0.01 M aqueous sodium chloride solution. No observable effect was observed on the phase boundaries by replacing pure water with brine solution in the case of R (+)-limonene based microemulsions. In the systems based on isopropylmyristate and caprylic-capric triglyceride, the replacement of pure water by brine significantly affected the phase boundaries, the microemulsion region shrink and the total monophasic area of microemulsions decreased. Electrical conductivity increases with the increase in the water volume fraction and percolation thresholds were observed. The critical volume fractions where the percolation thresholds appear depend on the type of oil used in the microemulsion formulation. Electrical conductivity was measured at different temperatures and the activation energy of conduction flow was evaluated. At the percolation threshold the activation energy of conduction flow reaches a minimum value. Beyond the percolation threshold, a small increase is observed in the activation energy of conduction flow then it decreases with the increase in the water volume fraction indicating structural transitions.     

Viscous Flow Parameters of Mixed Nonionic Surfactants Microemulsions

The systems investigated were water/sucrose laurate/ethoxylated mono-di-glyceride/oil + ethanol. The oils were R (+)-limonene, isopropylmyristate and caprylic-capric triglyceride. The dynamic viscosity of the systems where the mixing ratio (w/w) of ethanol/oil and that of ethoxylated mono-di-glyceride/sucrose laurate equal unity were measured. Dynamic viscosity was measured as function of temperature at different water volume fractions. The measured viscosities for the samples in all of the systems decrease as the temperature increases. The thermodynamic parameters of viscous flow that include enthalpy, entropy, and Gibbs free energy were estimated. In all of the systems studied, the enthalpy of viscous flow remains constant as function of temperature and varies as the water content in the microemulsions vary. The entropy and the Gibbs free energy vary with both the temperature and the composition of the microemulsions. Linear relationships were observed between the enthalpy and entropy of viscous flow for the systems based on the three oils. The enthalpy-entropy compensation temperatures were determined and found to be 265, 349, and 322 K for the microemulsion systems based on R (+)-limonene, isopropylmyristate and caprylic-capric triglyceride, respectively.     

Micellization,Solubilization and Microemulsions

Ohne Zusammenfassung

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Micellization, Solubilization and Microemulsions

     

Solubilization of Styrene and Acrylamide Monomers in Microemulsions

Abstract

Phase diagrams of sodium dodecyl sulfonate (DS)/n‐butanol/styrene/water systems with variable amounts of styrene were constructed at 40°C, and the effects of styrene on microemulsion stability were studied. The solubilization of styrene in these O/W microemulsion systems was investigated by ¹H NMR methods. The results show that the solubilization site shifts from the palisade layer to the inner core of microemulsion droplets when the molar fraction of styrene reaches 0.312. The solubilization of acrylamide in cetyltrimethylmethyl ammonium bromide (CTAB)/n‐butanol/10% n‐octane/water reverse microemulsions (W/O) was studied with a ¹³C NMR method. It was found that the acrylamide was mainly solubilized in the Stern layer of droplets at low acrylamide levels. However, when the mole fraction of acrylamide approaches 0.428, the acrylamide penetrates into the palisade layer and is distributed along the hydrocarbon chain of the surfactant.     

单一及复合表面活性剂对联苯菊酯微乳液的影响

通过对单一及复合型表面活性剂水溶液临界胶束浓度(CMC)和表面张力(γcmc)的测定分析,研究了表面活性剂对以水为介质、环己酮为溶剂形成的联苯菊酯质量分数为2.5%微乳液相行为及稳定性的影响.结果表明,在几种单一非离子表面活性剂中,苯乙烯基苯酚聚氧乙烯聚氧丙烯醚嵌段型非离子表面活性剂EPE的γcmc最低,为28.18 mN/m;按m(EPE):m(SDBS)=2∶1形成的复合型表面活性剂水溶液的γcmc更低,为27.60 mN/m,有利于O/W型微乳液的形成,当其质量分数为10%时,配制联苯菊酯质量分数为2.5%微乳液的有效成分热贮分解率为2.35%.     

季铵盐型双子表面活性剂与十八醇的混合单分子膜

研究了双子表面活性剂12-2-16和12-2-12分别与十八醇(C18H37OH)在空气-水界面上混合单分子膜的π-A等温线. 在相分离表面压以下, 比较了不同表面压下和不同混合比单分子膜的混合表面过剩自由能ΔGMexo, 分析了双子表面活性剂与脂肪醇在空气-水界面上混合膜中的相容性. 结果表明, 12-2-16与C18H37OH在所有混合摩尔比下随着表面压增高, 自由能增大. 12-2-12与C18H37OH混合膜体系的相容性取决于两者的混合比, ΔGMexo随所加入C18H37OH摩尔分数的增加逐渐增大, 从异种分子间净的吸引作用转变到相互排斥作用体系, 转变点为C18H37OH加入量的摩尔分数0.65. 当混合为热力学自发过程时, 增大表面压将有利于混合; 而对相互排斥体系, 增加表面压将使体系内异种分子之间的相互排斥作用更大.     

Precision Dilatometry of Microemulsions with Anionic Surfactants

Density ρ, isothermal compressibility β_Т, and thermal expansion coefficient α are measured with high accuracy at 15 and 25°C for water-n-octane-sodium dodecyl sulfate-n-pentanol microemulsions with a water/oil weight ratio varying from 0.05 to 4. The internal pressure of the microemulsions is shown to be calculable from the results of dilatometric measurements. The phenomenon of temperature inversion is revealed for the temperature coefficient of internal pressure ΔP _i/ΔT of the microemulsions. The analysis of this coefficient makes it possible to distinguish between three regions of the structural state in the microemulsions and a continuous structural transition in the associated microemulsions.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 4, 2005, pp. 479–484.Original Russian Text Copyright © 2005 by Kartsev, Shtykov, Shtykova.     

Phase Behavior of Bicontinuous and Water/Diesel Fuel Microemulsions Using Nonionic Surfactants Combined with Hydrophilic Alcohol Ethoxylates

Bicontinuous and water-in-diesel microemulsions were formulated using single nonionic alkyl poly glycol ethers combined with hydrophilic alcohol ethoxylates. The phase behavior at temperatures ranging from 0°C to 50°C was investigated. Visual inspection as well as cross-polarizers were used to detect anisotropy. The fish phase diagrams were determined. The presence of the hydrophilic alcohol ethoxylates was necessary to initiate both types of microemulsions. Increasing the hydrophobic chain length of the surfactant led to a wider range of temperature stability at lower surfactant concentration. Meanwhile, increasing the ethylene oxide units in the headgroup by two units led to a phase diagram that is dominated by lyotropic liquid crystal. The formulated water in diesel microemulsions were tested experimentally in a 4-cylinder diesel engine. From this it is observed that the emissions of NO_x, soot, and CO₂ were reduced substantially compared to neat diesel, while for the CO the reduction occurs just at low load.      

Solubilization of Biologically Active Heterocyclic Compounds by Biocompatible Microemulsions

Russian Journal of Physical Chemistry A - Microemulsions based on biocompatible components with high water content are applied to increase the solubility of medicinal drugs of the heterocyclic...     

Mechanism of the Micellar Solubilization of Curcumin by Mixed Surfactants of SDS and Brij35 via NMR Spectroscopy

The micellar solubilization mechanism of curcumin by mixed surfactants of SDS and Brij35 was investigated at the molecular scale by NMR spectroscopy. Through the investigation of the micelle formation process, types and structures of mixed micelles and solubilization sites, the intrinsic factors influencing the solubilization capacity were revealed. For systems with α_SDS = 0.5 and 0.2, the obtained molar solubilization ratios (MSRs) are consistent with the MSR_ideal values. However, for α_SDS = 0.8, the solubilization capacity of curcumin is weakened compared to the MSR_ideal. Furthermore, only one single mixed SDS/Brij35 micelles are formed for α_SDS = 0.5 and 0.2. However, for α_SDS = 0.8, there are separate SDS-rich and Brij35-rich mixed micelles formed. In addition, NOESY spectra show that the interaction patterns of SDS and Brij35 in mixed micelles are similar for three systems, as are the solubilization sites of curcumin. Therefore, for α_SDS = 0.5 and 0.2 with single mixed micelles formed, the solubility of curcumin depends only on the mixed micelle composition, which is almost equal to the surfactant molar ratio. Although curcumin is solubilized in both separate micelles at α_SDS = 0.8, a less stable micelle structure may be responsible for the low solubility. This study provides new insights into the investigation and application of mixed micelle solubilization.     

Dissipative Particle Dynamics Study of Interfacial Properties and the Effects of Nonionic Surfactants on Hydrocarbon/Water Microemulsions

The aim of this work was to apply dissipative particle dynamics (DPD) mesoscopic simulations to study the interfacial orientation and the effect of the nonionic surfactant, hexaethylene glycol monododecyl ether (C₁₂E₆), on different (oil (dodecane)/water) microemulsion systems. The Hildebrand-solubility-parameter model and Flory–Huggins/Hansen-solubility-parameter (FH/HSP) model were combined to evaluate the DPD interaction parameter (a_ij) where the solubility parameters (δ_i) as DPD input parameters were preliminary validated by all-atom molecular dynamics (MD) results and experimental data. The interfacial property dependence of dodecane/water/C₁₂E₆ system on the oil/water (o/w) ratio and on the concentration of surfactant and orientation at the interface were investigated. It was found that the surfactant addition reduced the IFT of o/w interfaces and this reduction was more efficient for water-in-oil microemulsions (o/w ≤ 1).     

Effect of Adding an Amphiphilic Solubilization Improver, Sucrose Distearate, on the Solubilization Capacity of Nonionic Microemulsions

We have studied the effect of adding sucrose distearate (2C(18)SE) on the solubilization capacity of microemulsions formed in the water/C(12)EO(6)/n-decane system. Upon addition of 2C(18)SE to the binary water/C(12)EO(6) system, a lamellar liquid crystal region developed. This suggests that the rigidity of the surfactant layer is strengthened. The solubilization of water and n-decane in the bicontinuous microemulsions increases about three times upon replacing 10% C(12)EO(6) with 2C(18)SE; besides, the HLB temperature is not greatly affected by 2C(18)SE. On the other hand, sucrose monostearate (C(18)SE) does not have such a function. The effect of added 2C(18)SE on the solubilization capacity of the discrete droplet-type o/w or w/o microemulsions was also studied. The efficiency of the solubilization-improving effect is reduced when the system is far from the HLB temperature. Copyright 2001 Academic Press.     

Solubilization and Interactions of Thiram with Surfactants: Micellar Effects on Adsorption Characteristics of Thiram onto Activated Carbon

The solubilization of thiram was studied in micellar solutions of two surfactants possessing the same hydrocarbon tail but different hydrophilic head groups, namely sodium dodecyl sulfate and dodecyltrimethylammonium bromide. Conductivity, spectrophotometry, and surface tension measurements have been used in quantitative analysis of the interaction between thiram and surfactants. In this work the adsorption of thiram onto selected two different activated carbons has been also studied in the absence and presence of micelles. The interaction of thiram in different micellar solutions provided information about the characteristics of adsorption properties of poorly soluble pesticide thiram onto activated carbon in the presence of micelles.     

助表面活性剂对阴/阳离子表面活性剂复配形成微乳液的影响

中相微乳液;盐度扫描;助表面活性剂对阴/阳离子表面活性剂复配形成微乳液的影响