Emulsions and Interfacial Properties

The control of emulsification and emulsion stability is of great interest for a large number of applied fields and is strictly related to the adsorption properties of emulsifiers at water–oil interfaces. This chapter focuses on the effects of interfacial properties on the major mechanisms governing the aging of emulsions and emulsification. Besides a summary of the consolidated background and experimental methods, some results from recent literature on the topic are reported, discussing some criticalities. The typical experimental approaches recently adopted to investigate emulsions and the role of the relevant features of the emulsifier are reported. These are, for example, their adsorption properties at the droplet interface and their affinity with the two liquids composing the emulsion. Different types of surface-active species used as emulsifiers or emulsion stabilizers are considered, including solid particles or surfactant–nanoparticle complexes. The latter is of great interest in a wide variety of emulsion-related products and technological fields. Among the relevant experimental approaches, the focus here is on correlation spectroscopies, like diffusing wave spectroscopy (DWS), empowered by detailed numerical modeling. This is exemplified by experimental campaigns aboard space laboratories, which exploit microgravity conditions as optimal environments to investigate the intrinsic dynamics of droplet populations in emulsions.