Influence of the Oil on the Properties of Microemulsions as Reaction Media

Abstract

The influence of the nature of the continuous medium on various properties of a wide range of water‐in‐oil (w/o) microemulsions was examined. 1H NMR spectroscopy allowed to determine the properties of water in the studied systems and the way they are affected by the solvent to be elucidated. Changes in interfacial polarity were examined from the 13C NMR signals of the surfactant molecule sodium bis(2‐ethylhexyl)sulfosuccinate (AOT). Chemical shifts were found to vary with the water content of the microemulsion. The variation of the carbon chemical shift as a function of the water‐to‐surfactant concentration ratio (W) was used as an indirect measure of polarity changes at the microemulsion interface. The kinetic effects of the microemulsion composition on the solvolysis of anisoyl chloride were studied, and the reagent was found to react with water at the microemulsion interface alone. Based on both kinetic and NMR results, the solvolysis rate constants of anisoyl chloride decrease with increasing penetration of the oil into the interface. Also, the resonance signals for the water H atoms were found to change in parallel with the solvolysis rate constant for anisoyl chloride. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

On the Investigation of the Droplet–Droplet Interactions of Sodium 1,4‐Bis(2‐ethylhexyl) Sulfosuccinate Reverse Micelles upon Changing the External Solvent Composition and Their Impact on Gold Nanoparticle Synthesis

“…[19,21,44] As it is difficult for larger solvent molecules to penetrate the interface, the differences would increase and so would the magnitude of the droplet-droplet interactions. [10,26,46,47] The RM droplet sizes depend, among many other variables, on the effective packing parameter of the surfactants, v/al c , in which v and l c are the volume and the length of the hydrocarbon chain, respectively, and a is the surfactant head group area. The surfactants are optimally packed and, hence, have a larger network attraction.…”

“…For example, at a fixed temperature within the reverse micellar stability region of the phase diagram, the interaction is manifested by an increase of the droplet size. [14][15][16] Although the properties of RMs depend on the type of surfactant, the W 0 values, [1][2][3][4]24,25] and the external nonpolar organic pseudophase, little research has been performed on the influence of the organic media for AOT, [10,[26][27][28][29][30][31] and this influence has only been investigated very recently for the cationic RMs formed with the benzyl-n-hexadecyldimethylammonium chloride (BHDC) surfactant. [17,18] Lemaire et al proposed that the attractive droplet-droplet interactions depend on the mutual interpenetration of the surfactant tails over some small distance without much entropy loss and a decrease in the total free energy of the system.…”

“…[17,18] Lemaire et al proposed that the attractive droplet-droplet interactions depend on the mutual interpenetration of the surfactant tails over some small distance without much entropy loss and a decrease in the total free energy of the system. [26] To the best of our knowledge, there are no studies of AOT RMs that use a molecular probe to investigate the effect of the external nonpolar solvent on the interfacial properties within the reverse micellar phase of the phase diagram, which is far from the percolation of the system. At a fixed temperature, the solvent molecules are not optimally oriented to interact with the surfactant tails, whereas the surfactant tails of two different RMs in the overlap region are always more or less parallel to each other.…”

Evaluation of proton activity in microemulsions by a kinetic probe

“…To extend the working temperature to the broadest range of a values attainable, the composition of the two microemulsions and the temperature were carefully selected to accomplish the kinetic experiments according to the respective phase behavior. This gathering of experimental conditions along with the close features of the two hydrocarbons [15] made it feasible the carrying out of kinetic experiments over a sufficiently broad range of proton concentration.…”

Organic Reactions in Microemulsions

“…This was investigated in a recent work using a chemical reaction, hydrolysis of anisoyl chloride, as a probe. [39] Anisoyl chloride is oil soluble and slightly polar. It can be expected to partition between the oil domain and the interface and the hydrolysis reaction will only occur at the interface.…”