by The Cosmetic Chemist Staff
November 22, 2021
Emulsions are important formulation vehicles that are found in many types of products in the personal care market place. Essentially, an emulsion is a mixture of two or more liquids, usually immiscible, where one of the components is uniformly dispersed as droplets (dispersed phase) in the continuous phase. At the very basic level, there are two types of emulsions: oil-in-water (O/W) and water-in-oil (W/O). It should be noted, however, that emulsion chemistry is in fact very complex from the standpoint of colloid and physical chemistry as well as processing technology.
Emulsions are thermodynamically unstable due to the high interfacial tension between the dispersed and continuous phase and require the use of emulsifiers to provide stability. Most conventional emulsions contain surfactants, which help emulsify, solubilize, disperse the discontinuous phase, and stabilize the emulsion. In a recent review of the literature, Amin and coworkers examine the feasibility of using particles to carry out these functions in emulsions.1 Already around for some time, Pickering emulsions employ the use of small solid particles to stabilize the interfacial region of the dispersed and continuous phase.
In some cases, surfactants are used in conjunction with microparticles or nanoparticles (e.g., TiO2 and silica). Janus particles are amphiphilic, surface-active entities that have been used in emulsions in other industrial areas. Janus particles typically have two or more distinct properties. For example, part of the particle’s surface may contain hydrophilic functionality while the other section may have hydrophobic characteristics. While there has not been much research focused on the use of Janus particles in cosmetics, this could offer the necessary flexibility to create and stabilize complex emulsion systems. Overall, the use of particles instead of surfactants could lead to the development of more sustainable formulations.
1. D. Venkataramani, A. Tsulaia, and S. Amin, Fundamentals and applications of particle stabilized emulsions in
cosmetic formulations, Adv. Coll. Inter. Sci., 283, 102234 (2020).