Improving the emulsion stability by regulation of dilational rheology properties

Considering the importance of interfacial film in determining emulsion stability, it is of great significance to reveal the relationship between the emulsion stability and rheology properties. Herein, we first investigated the dilational rheology properties of the imidazolium Gemini surfactants ([Cn+2-3-Cn+2im]Cl2) by the oscillating drop method, and the [C14-3-C14im]Cl2 was selected as the emulsifier due to its excellent rheology properties. Based on the rheology results, [C14-3-C14im]Cl2 was further complexed with Brij®S10 in the decane to prepare a series of O/W emulsions through the inversed phase emulsification method. Subsequently, the stabilities of these emulsions were systemically characterized, including the droplet diameter, polydispersity index, demulsification test and long term stability. After careful evaluation of the rheology properties and the emulsion stability, the relationship between them was revealed, which was the larger the dilational modulus is, the better the emulsion stability will be. This phenomenon was further explained by the variation trend of droplet radius with time. Moreover, a thick interfacial film with large dilational modulus would lead to the decrease of the Ostwald ripening rate, coalescence rate, and creaming rate, finally resulting in the increase of the emulsion stability. These findings will further provide guidelines for the selection of surfactants and the preparation of stable emulsions.