One-Step Multiple Emulsions Driven by Interfacial Neutralization Reaction

The multicomponent structure and the large area of oil–water interfaces make multiple emulsions promising for use in cosmetic manufacturing, food industries, and agricultural production. However, the high energy input and extensive use of emulsifiers in the process of multiple emulsion preparation severely limit their application. In this work, we propose a simple but highly efficient emulsification strategy to realize one-step multiple emulsions. To this end, the interfacial acid–base neutralization reaction by oleic acid and ammonia is employed as the driving force to construct a spontaneous emulsifying system, thus realizing emulsion formation in a low-energy manner. Moreover, the products generated by the interfacial neutralization reaction can act as emulsifiers to stabilize both the O/W and W/O interfaces and construct multiple emulsions with an O/W/O structure. Compared to conventional methods of multiple emulsion formation, the one-step multiple emulsion method driven by an interfacial neutralization reaction can significantly reduce the energy consumption and the emulsifier dosage during the emulsifying process, thus avoiding the probable environmental problems caused by the residual emulsifiers. This study not only provides a new idea for the preparation of multiple emulsions but also effectively promotes the development of low-surfactant emulsification methods.