Investigating Short-chain Alcohol Based Microemulsions as Viable Nanoparticle Synthesis Systems: Do Reverse Micelles Form in Ethanol/AOT/n-Heptane Systems?


Through a fundamental study on the effects of ethanol on the phase behavior of sodium bis(2-ethylhexyl) sulfosuccinate (AOT), particularly its ability to form reverse micelles in n-heptane, we consider the efficacy of ethanol/AOT/n<-heptane systems for monodisperse nanoparticle synthesis. Using dynamic light scattering, molecular dynamics simulations, and 1H NMR spectroscopy, we investigate the aggregation behavior of AOT across a wide range of ethanol/AOT/n-heptane compositions. We identify mixed-solvent polarity as a driving factor for surfactant behavior in the system, and conclude reverse micelles do not form at any investigated compositions and likely cannot form in this system regardless of composition. However, other unique surfactant aggregate morphologies which offer new possibilities for nanoparticle shape control, including multilayered cylindrical structures and spherical AOT-in-ethanol structures, are found in this system. A preliminary phase diagram for the ethanol/AOT/n-heptane system is constructed from our results, proving useful in continued studies on system behaviors and synthesis potential.

San Diego, California