Formation of Microemulsions in Mixed Ionic−Nonionic Surfactant Systems

In this study the effect of an anionic surfactant (sodium dodecyl sulfate SDS) and oils (hydrocarbons: C12-C16) on the formation and phase behavior of the systems of oil/monoacylglycerols (MAG):SDS/propylene glycol/water has been investigated. The effects of the surfactant mixture on the phase behavior and the concentration of water or oil in the systems were studied at three temperatures (50, 55, 60°C). Electrical conductivity measurement, FT-IR spectroscopy and differential scanning calorimetry methods were applied to determine the structure and type of the microemulsions formed. The dimension of microemulsion droplets was characterized by dynamic light scattering. It has been stated that the concentration of SDS has a strong influence on the shape and extent of the microemulsion areas. Addition of an ionic surfactant to the mixture with MAG promotes an increase in the area of microemulsion formation in the phase diagrams, and these areas of the isotropic region change with the temperature. It was shown that the presence in the systems of a surfactant more hydrophilic than MAG caused an increase in water content in the microemulsions. It was found that, depending on temperature and concentration of the surfactant mixture, it was possible to obtain a W/O type microemulsion with a dispersed particles size distribution ranging from 20 to 50 nm and containing about 17-38% water in the system. Among different alkanes (from C12 to C16), hexadecane embedded microemulsions showed a maximum water solubilization capacity. Keywords Microemulsions Á Monoacylglycerols Á Sodium dodecyl sulfate Á FT-IR Á DSC Á DLS Abbreviations FTIR Fourier transform infrared MAG Monoacylglycerols ME Microemulsions MLS Multiple light scattering PG Propylene glycol (1,2-propanediol) SDS Sodium dodecyl sulfate

Section: Phase Behavior Of Monoacylglycerols-sodium Dodecyl Sulfate (mentioning

confidence: 99%

Effect of Alkyl Sulfate on the Phase Behavior of Microemulsions Stabilized with Monoacylglycerols

Szeląg

Szumała

2010

“…The activity coefficients are related to the interaction parameter in the mixed monolayer β S and the molar fraction in the mixed monolayer by the relationship approximated using the second term of the Margules expansions: [8] [9]…”

Section: Resultsmentioning

confidence: 99%

Synergism in mixed monolayers of alkylpolyglucoside and alkylsorbitan surfactants at liquid/liquid interface

Cintezã

Dudau

2003

A study of nonideal behavior in the formation of mixed monolayers at the oil-water interface was performed for a nonionic-nonionic surfactant system. Mixtures containing alkylpolyglucoside and alkylsorbitan derivatives were investigated. As the oily phase, colza-rapeseed and olive oils were used. To evidence a synergetic effect in the interfacial tension reduction in the oil-water-surfactant-cosurfactant system, the model based on the regular solution theory was modified for the case of both surfactants being soluble in the water as well as in the oily phase. For determination of the condition for the synergism and the point of the maximum synergetic effect, the molar fraction in the mixed monolayer X S and the interaction parameter β S were calculated, using experimental data for the interfacial tension and for the partition coefficient. A set of general equations was developed, to allow the analysis of a mixture containing a water-soluble and an oil-soluble surfactant. The equations are applied according the characteristics of studied quaternary systems. The mathematical model was tested with literature data, and the results were compared with those obtained from the phase diagram of oil-water-mixed surfactant system. The systems water-vegetable oil-alkylpolyglucosidealkylsorbitan show a maximum synergetic effect at molar fractions between 0.85 and 0.90. The liquid-liquid interfacial tension and partition coefficient data were used to calculate the point of the maximum synergetic effect, i.e., the surfactant-cosurfactant ratio, which ensures the interfacial tension minimum. The dramatic reduction in interfacial tension due to the presence of the surfactant mixture at the interface at the point of the synergism maximum is related to the formation of threephase and single-phase microemulsions. The results were applied to obtain single-phase microemulsion in water-vegetable oil-alkylpolyglucoside-alkylsorbitan systems.Paper no. S1348 in JSD 6, 259-264 (July 2003) KEY WORDS: Liquid-liquid interface, microemulsion, mixed surfactant system, synergism.The nonideal behavior of surfactant mixtures is of interest from both a theoretical and a practical point of view. Most industrial applications of surfactants involve the use of mixed surfactants or technical surfactants, which can be considered to be a mixture of surfactants. The existence of synergetic effects in mixed surfactant systems has been studied for several decades, but the published results have been based on a qualitative approach to this behavior, and quantitative analysis has been reported only for some particular cases. Some mathematical models were elaborated to study the nonideal behavior of the mixed surfactant systems. Rubingh (1,2) devised a model based on regular solution theory, as applied to the mixed micellization process in the aqueous solution of mixed surfactants. One can calculate the molar fraction of the surfactant in the mixed micelle and the interaction parameter in the mixed aggregate from the variation of critical micelle concentrations...

“…1) we were able to derive values of the periodicity, d, and the correlation length, n, as described in the experimental section (Eqs. 3,4). The dependence of the d and n parameters on the volume fraction of water, / for the system is presented in Figs.…”

Section: Structural Parametersmentioning

confidence: 99%

“…In the majority of industrial pharmaceutical, cosmetic and food applications, mixed surfactants rather than single ones are used for the formulation of microemulsions [1][2][3][4][5]. Mixtures of nonionic surfactants are more effective than the other classes of surfactants because of their effectiveness at lowering the monomer concentration and their lower risk of precipitation.…”

Section: Introductionmentioning

confidence: 99%

“…Mixtures of nonionic surfactants are more effective than the other classes of surfactants because of their effectiveness at lowering the monomer concentration and their lower risk of precipitation. The incorporation of another surfactant into the mixture of two immiscible phases and surfactant provides an additional degree of freedom, which enhances the mutual solubility and enables the adjustment of phase behavior [1][2][3][4][5][6][7]. The use of nonionic surfactants for the formulation of microemulsions needs in some cases the use of alcohol or acid as co-surfactants [8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

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Microemulsions with Mixed Nonionic Surfactants and Flavor Oil

Fanun

2010

The microemulsion systems composed of water/sucrose laurate/ethoxylated mono-di-glyceride/peppermint oil were formulated and characterized using electrical conductivity and small-angle X-ray scattering. The solubilization capacity of water in the oil is dependent on the surfactant mixing ratio. A static percolation phenomenon was observed in these systems and the water volume fraction percolation threshold was determined. A progressive transformation of water-in-oil to bicontinuous microemulsions, occurring upon dilution with water was revealed for equal amounts of sucrose laurate and ethoxylated mono-di-glyceride in the microemulsions. The periodicity, that is a characteristic length for the domain size of the microemulsions, increases linearly with the increase in the water volume fraction, whereas the correlation length, that is also a characteristic length for the domain size, increases with the increase in the water volume fraction up to a certain value then decreases.