Investigating the effect of different molecular weights of polyethylene glycol (PEG) on the viscosity of the continuous phase in oil-in-water (O/W) emulsions using fluorescence microscopy and emulsion tracking technique
An oil-in-water (O/W) emulsion is a mixture of two immiscible liquids in which small oil droplets are dispersed in a water phase. During storage, emulsion droplets may undergo thermodynamic and breakdown processes, for example, creaming which can lead to phase separation. The addition of emulsifiers can delay these processes. In this study, the effect of varying molecular weights of polyethylene glycol (PEG), a hydrophilic linear polymer, as a co-emulsifier in the continuous phase of an O/W emulsion was investigated. A new approach is established using fluorescence microscopy and an emulsion tracking algorithm to measure the viscosity and diffusibility of individual droplets in the continuous phase. Emulsion tracking provides insights into the local mechanical behavior of the system. Results indicate that higher molecular weight PEG solutions increase the viscosity of the continuous phase, resulting in less diffusibility of the droplets. This novel approach provides a deeper understanding of the physicochemical properties of emulsion.