Coalescence in Double Emulsions: Distinction of Coalescence Paths with Model Experiments

Double emulsion are a promising system for the encapsulation of water soluble actives in water based formulations. Achieving droplet stability against coalescence requires the use of two different species of surfactants. This work discusses the competitive adsorption of these two surfactants at the two differently curved interfaces found in double emulsions and the consequences on emulsion stability. The stability of the system is assessed through three different model experiments: Single droplets, microfluidic emulsions and single emulsions. The advantages and challenges of the measurement systems are discussed and formulations for stable double emulsions are suggested.