Pickering emulsions have attracted a great of interest in the personal care and pharmaceutical industry due to their stability to coalescence. Clay particles are often used as stabilizers to produce oil-in-water or water-in-oil Pickering emulsions depending on the contact angle of the particle at the oil-water interface. In this work, we utilize a synthetic clay particle, Laponite®, to create oil-in-water emulsions, and explore the addition of charged and non-charged surfactants. In this study, the stability of Pickering emulsions with and without surfactants (dodecyltrimethylammonium bromide (DTAB), Pluronic F68, and sodium dodecyl sulfate SDS) are investigated using dynamic light scattering (DLS), ζ-potential, optical microscope, and rheology. The DLS and ζ-potential results show an average droplet size of 3 µm and the ζ-potential of -90 mV. With the addition of surfactants, both the droplet size and ζ-potential increase, suggesting absorption of surfactants on the surface of Laponite® particle. The microscopic images suggest that the stability of the Pickering emulsion without surfactant is enhanced by flocculation, while the emulsion becomes stable to coalescence and creaming with addition of surfactants due to formation of network structure. Interestingly, regardless of the formation of this network structure, the Laponite®/F68 emulsion behaves rheologically as a Newtonian fluid, while the emulsions of Laponite® and both SDS and DTAB display a higher viscosity and shear thinning behavior. We attribute the difference in the rheological behavior to the weak absorption of F68 on the Laponite® surface, and to electrostatic interactions between Laponite® and charged surfactants at oil-water interface.

Pickering emulsion stabilized by clay particle and surfactants

256th National Meeting (2018)

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