Structure and thermodynamics of Pickering emulsions stabilized by adsorbed charged particles

Abstract

In this work, we reexamine the problem of the stabilization of the Pickering emulsions by an adsorption of small charged particles on the surfaces of droplets of some liquid dispersed in another unlike liquid. Quantitatively, such a problem is naturally studied through the determination of the structure and thermodynamics of these emulsions. To this end, we first regard droplets as monodisperse small spheres assimilated to charged soft-colloids. For the sake of simplicity, the adsorbed particles are assumed to be point-like. When the temperature of the considered emulsions is fixed (room temperature), the only remaining parameters of discussion are the droplet number density, their size and surface charge, and the concentrations of counterions and ions (in the presence of a salt or an electrolyte). For the study, we adopt the Sogami-Ise pair-potential between anchored droplets that reproduces well the features of the real DLVO’s one. The structure (through the structure factor and spatial correlation-function) and thermodynamics (through the pressure, internal energy and thermal compressibility) are computed using, first, Integral Equation Method, with Hybridized Mean Spherical Approximation, and second, the Molecular Dynamic Simulation. The structure factor and the correlation-function and thermodynamical quantities are discussed in terms of the droplet density, their size and surface charge. Finally, we compare the results from these two methods, and find that they are in good agreement.