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

Abstract

Simple procedures and characterization of a series of well-defined precursors are described for preparation of a unique microenvironment in nanoreactors, reverse micelles. The Na(+), K(+), Rb(+), Cs(+), and Mg(2+) surfactants were prepared using liquid-liquid ion exchange using chloride and nitrate salts. The surfactants were characterized using (1)H NMR spectroscopy and a variety of other techniques. (1)H NMR spectroscopy was found to be a sensitive probe for characterization of the size of the nanoreactor as well as its water content. (1)H NMR spectra can be used for detailed characterization of reactions in confined environments when counterion effects are likely to be important. (1)H NMR spectroscopy revealed two separate peaks corresponding to water in Mg(AOT)2 samples; one peak arises from water coordinated to the Mg(2+) ion while the other peak arises from bulk water. The two water signals arise directly from the slow exchange of the water coordinated to Mg(2+) in these microemulsions with water in the water pool, and provide an opportunity to study hydration of Mg(2+). This work thus extends the potential use of MAOT microemulsions for applications such as in green chemistry.

Counterion Affects Interaction with Interfaces: The Antidiabetic Drugs Metformin and Decavanadate

“…Sodium bis(2-ethylhexyl)sulfosuccinate (AOT, Sigma-Aldrich, 98.0 %) was purified as described previously. [21,84] Doubly distilled water was used for all reverse micelle systems. …”

Molecular characterization of water and surfactant AOT at nanoemulsion surfaces

“…Previous studies indicate that Mg 2+ has a higher degree of water association with ratios of water molecules/counterion found to be 0.002, 0.6, and 2.7 for Na + , K + , and Mg 2+ , respectively. The 1 H NMR showed this water association with the ion is also present for Mg:AOT in microemulsions (48). Fig.…”

“…Changing the counterion associated with AOT has been shown to have an effect on water bonding in the interior of the micelle (48,51). Shown in Fig.…”

Gel Formulation Containing Mixed Surfactant and Lipids Associating with Carboplatin

“…These materials were used without further purification. Sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was purchased from SigmaAldrich (St. Louis, MO) and purified as reported in [74] to remove an acidic impurity. Deionized water (Barnstead E-pure system) with specific resistivity of 18 MW cm was used for sample preparation.…”

“…(pH 7.0) into 0.5m Na(AOT) stock in isooctane to yield translucent single-phase solns. The 1 H-NMR spectra were acquired at 218 on a Varian Inova 400 spectrometer operating at 400.131 MHz, using the unlocked mode settings without 2 H lock, as reported in [74] for these complex samples, because the addition of 3. Langmuir Monolayer Film Preparation and Surface PressureÀArea Isotherms.…”