Pickering emulsions stabilized by stimuli-responsive microgels: study of their stability

Abstract

Emulsions are a type of dispersing system that consists of two liquids that are incompatible with one another. Emulsions can be made stable by employing microgels (so-called Pickering emulsions) as stabilizers. Microgel-stabilized emulsions have unique features because of the rigidity of the surfaces as microgels are soft and deformable colloidal particles that are swollen by a solvent and exhibit the capacity to deform and adsorb at liquid interfaces. This study aims to comprehend the relationship between the parameters influencing the interfacial properties of emulsions and their mechanical behavior. The first section of the result addressed the formation of emulsions by means of rotor stator homogenization that is driven by limited coalescence phenomenon. Then, the compression behavior of the emulsions was determined by measuring the relationship between osmotic pressure and droplet’s volume fraction after they are centrifuged and examined the effect of microgel’s cross-linking density and their size, the nature of the oil phase, as well as formulation process (emulsification procedure) on the emulsion’s flocculation state and compression behavior. The results were interpreted in terms of the elasticity of the adsorbent particles due to the presence of intrinsically attractive contacts, which proved that the interface of microgels-stabilized drops exhibits the linear relationship between stress and strain that is typical of elastic behavior. As a result, small size microgels of the 2.5% BIS type appeared to be the most suitable for obtaining non-flocculated and kinetically stable emulsions with the highest osmotic pressure and droplets volume fraction as well as linear behavior in interpretation which confirmed the elastic behavior of the emulsion.