Effect of cations on the structure of sodium bis(2-ethylhexyl)sulfosuccinate water-in-oil microemulsion

Abstract

We have characterized the structure of water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane water-in-oil microemulsion depending on the concentrations of monovalent and divalent cations (Na + , K + , Ca 2+ ) in the water pool. We have found that the presence of salts affects the microemulsion structures differently at low and high water contents. Increasing the salt concentration suppresses the oligomerization of the microemulsions at low water content, whereas it reduces the microemulsion radius at high water content. The present results clearly indicate that not only electrostatic repulsion between AOT headgroups but also negative or positive hydration effects by salts dominate the structure and dynamics of AOT microemulsions, as suggested by a recent molecular dynamics simulation.

1H NMR Studies of Aerosol-OT Reverse Micelles with Alkali and Magnesium Counterions: Preparation and Analysis of MAOTs

“…Traditionally, TGA is used to measure the water content in solid materials but it can also be used with liquid samples . We also made Karl Fischer titration measurements both to gauge how well the TGA worked for water content determination of our samples and to be consistent with other reports in the literature. ,– As shown in Table , the water content ranges from 0.002 to 3 equiv of water for each MAOT surfactant that we have prepared. Both Karl Fischer titration and TGA measurements agree with each other that our materials are consistently drier than literature reports .…”

“…TGA is a convenient and sensitive method to determine water content. However, water content is customarily determined using Karl Fischer titrations in microemulsions ,– , and we therefore used Karl Fischer titrations on samples we had investigated using TGA. As shown in Table , our preparations are found to contain similar or smaller amounts of water compared to previous reports in the literature. ,,,, Presumably, the dryness of our samples is in part due to extended drying times under vacuum (up to 12 h).…”

Composition of Commercial Bis(2‐ethylhexyl) Sulfosuccinate Surfactant By‐Products and their Effects on an Agrochemical Formulation

“…Nevertheless, they may still influence the sedimentation process and should not be neglected in future investigations of the sedimentation process. Several papers are dedicated to the analysis [13,[23][24][25][26][27][28] and properties [1,[28][29][30][31][32][33] of AOT in various media and its uses, but the findings observed here, which might be attributable to the interactions of AOT with its monoesters, have not been discussed elsewhere to the knowledge of the authors. However, these results suggest that the main-and by-product spectra of surfactants from different suppliers must have similar chemical compositions to ensure the consistent behavior of complex mixtures containing surfactants, such as agrochemical formulations.…”

“…Samples of a model agrochemical formulation made using the different AOT products aged differently: storage tests revealed that an increased content of monoesters in the AOT product used correlated with increased sedimentation during storage. There are several papers dedicated to the analysis [13,[23][24][25][26][27][28] and properties [28][29][30][31][32][33] of AOT in various media and its uses, but little has been published on the interactions of AOT with its monoesters in complex mixtures such as agrochemical formulations. Although the fundamental behaviors of mixtures of different surfactants are well understood [5,19], predicting their interactions in complex mixtures such as agrochemical formulations has been shown here to require more research.…”

Self-assembly of amphiphilic molecules: A review on the recent computer simulation results

“…Despite of the extensive application in traditional chemical industry, emulsion and microemulsion systems are widely used in drug delivery systems, synthesis process of nanostructured materials and the process of oil extraction [1,21]. Some experimental and theoretical studies [127][128][129][130][131][132][133][134] have been carried out in order to understand the phase behaviors of microemulsion systems and their corresponding static structures, and some simulation studies intend to provide information on the stability of microemulsion systems and dynamic process of solute dispersion and exchange. Using dissipative particle dynamics simulations, Li et al [127] recently investigated the kinetic process of a collision-driven solute exchange in an aqueous phase in which micelles are used as solute carriers.…”