Formulation variables influencing the properties and physical stability of green multiple emulsions stabilized with a copolymer

To obtain multiple emulsions containing Agnique™ AE 3-2H as oil phase and Atlas™ G-5000 as emulsifier, two formulation variables were studied: the effect of the Atlas™ G-5000 concentration in emulsions containing 15 wt% Agnique™ AE 3-2H and the study of the influence of the solvent concentration maintaining the Agnique™ AE 3-2H/Atlas™ G-5000 ratio equal to 10. To assess microstructure and physical stability of these emulsions different techniques were employed, namely laser diffraction, transmitted light optical microscopy, steady-state measurements, and multiple light scattering. An increase in copolymer concentration and solvent concentration provoked a decrease in Sauter diameter but an increase in volume mean diameter and polydispersion due to droplet coalescence. Regardless of polymer concentration, all emulsions showed Newtonian behavior which led to shear thinning with increasing oil concentration. The main destabilization processes are creaming, when the concentration of polymer or solvent is low, and coalescence, when both concentrations are high.