The use of binary mixtures of surfactant and colloidal particles is of great academic and commercial interest for the stabilization of emulsions and foams. Depending upon the interactions between the surfactant molecules and the colloidal particles, and on the relative concentrations of surfactant to particles, the formed emulsions can exhibit different properties. Surfactant molecules of charge opposite to that of the colloidal particles modify the wettability of the particle surfaces by exposing their hydrophobic tails to the aqueous phase. On the other hand, surfactant molecules of charge similar to that of the colloidal particles, may not interact with the colloidal particles as a result of the electrostatic repulsions between them. Nonionic surfactants can interact with colloidal particle surfaces through hydrogen bonding or hydrophobic interactions. The resulting surfactant adsorption behavior can greatly affect the colloidal particles dispersion stability and wettability, in turn affecting the formation and stability of the emulsions. In this poster, I will discuss general aspects of the formation and stability of emulsions, as they are affected by the addition of surfactants and colloidal particles. I will show that irrespective of the surfactant-particle interactions, surfactant-stabilized emulsions are always favored at high surfactant-to-particles ratios. On the other hand, I will show that phase separation of oil and water, or emulsions stabilized by both particles and surfactant molecules, are observed at intermediate surfactant-to-particle ratios. These findings will be explained using a combination of visual and microscopic observations, as well as surface tension measurements.
Colloids and Interfacial science, Surfactants and Emulsions, Sol-gel Synthesis, Micro- and nano-fabrication, Patterning of Soft Surfaces, Rheology, Environmental Remediation
Thermodynamics, Colloids and Interfacial phenomenon