Cosurfactant Leads to Successful Dilute Emulsion Formation Via Microemulsion

Cosurfactants play an important role in self-emulsification in three-component systems (water, oil, and non-ionic surfactant). The addition of a very small amount of cosurfactant can abruptly change the interfacial tension and curvature. It can determine the region of composition/temperature producing stable microemulsions. Such one-phase microemulsions have been known to serve as useful precursors to nanoemulsions – dilute long-lived emulsions of nanoscale droplete.

Here, we create very stable vesicular structures from the microemulsions; we found that a sufficient amount of cosurfactant determines the success of microemulsion processing. We have investigated the phase behavior of water/n-hexadecane/nonylphenol ethoxylates system and created kinetically stable nanoparticles.

To study this, we use three complementary methods: cryogenic transmission electron microscopy (Cryo-TEM), cryogenic scanning electron microscopy (Cryo-SEM), and freeze-fracture electron-beam evaporated replicate TEM (FF-TEM).  The complementary use of these techniques shows the behavior of these complex fluid microstructure transitions at multiple scales.  Cryo-TEM alone cannot show crucial, large-scale structures, but cryo-SEM can. Cryo-SEM alone cannot show where the oil is, but FF-TEM can.