Oil in Water with Amphiphilic Surfactant

Simulations of sheared emulsions of oil- in water stabilized by an amphiphilic surfactant

Oil-in-Water Emulsions with Amphiphilic Surfactant

Oil and water are inmiscible, still, on the molecular scale both phases will diffuse into each others domains and can bridge small domains of the opposite phase leading to coalescence of droplets. Only a stabilizing mechanism significantly reducing this diffusion and with repulsion between interfaces of opposite orientation results in stable droplets. That is the role of surfactants.

An amphiphilic surfactant is a molecule with end groups that prefer the opposite phases eg it might have a hydrophilic head and a hydrophobic tail. Surfactant molecules minimize their interaction energy by migrating to the fluid interfaces. There, their orientation aligns with the concentration gradient. They enhance the repulsion between the two fluid phases and repel each other if the orientation is anti-parallel.

We have run simulations of a ternary fluid (three components: water, oil, surfactant) in shear flow with a surfactant with amphiphilic properties.

The simulation model allows to explore the effect of the surfactant on the emulisification of the system, its microstructure e.g. droplet size distribution, and its stability under shear flow.