Characterization of Cationic Polyelectrolytes Adsorption to an Anionic Emulsion via Zeta-Potential and Microcalorimetry

The adsorption of cationic polyelectrolytes (PEs) onto anionic silicone emulsion droplets, suspended in a sodium chloride solution is studied via electrophoretic mobility measurements and isothermal titration calorimetry. These model systems are studied to better understand the interactions governing PE adsorption-induced emulsion flocculation, which is relevant to many industrial applications. Electrophoretic mobility measurements provide critical information for rationalizing the effect of the PE charge density on the loss of stability of silicone emulsions. The interaction strength is calculated from a Langmuir adsorption isotherm determined by a ζ-potential titration measurement. Microcalorimetry measurements independently validate the adsorption free energy. Emulsion flocculation and coacervation are observed in the visual phase behavior as well as the ζ-potential titration measurements. The effect of PE charge density shows that PE-surfactant coacervation is the driving force in these PE-emulsion systems.