Theories of Emulsification

Surface Tension Theory

• Liquids tend to minimize their surface area by forming spherical shapes, which have the least surface area.
• Surface tension is a force that resists the formation of smaller droplets when two immiscible liquids come into contact.
• Emulsifying agents reduce interfacial tension, diminishing the repellent force between the liquids and each liquid's attraction to its own molecules.
• Emulsifiers lower the interfacial tension, facilitating the breaking up of large globules into smaller ones, which then have a lesser tendency to reunite or coalesce.

Oriented-Wedge Theory

• Emulsifying agents form monomolecular layers around the droplets of the internal phase.
• Emulsifying agents are preferentially soluble in one of the phases and are embedded more deeply in that phase than the other.
• Molecules with a hydrophilic and hydrophobic portion orient themselves in each phase based on their solubility.
• Hydrophilic emulsifiers promote o/w emulsions, while hydrophobic emulsifiers favor w/o emulsions.
• The phase in which the emulsifier is more soluble becomes the continuous phase of the emulsion.

Plastic or Interfacial Film Theory

• Emulsifying agents form a thin film at the interface between the immiscible liquids, adsorbed on the surface of internal phase droplets.
• The film acts as a barrier, preventing contact and coalescence of the dispersed phase.
• The stability of the emulsion depends on the toughness and flexibility of this film.
• The degree of solubility of the emulsifying agent in the two phases determines whether o/w or w/o emulsions are formed.

Learn about the different theories of emulsification, such as the Surface Tension Theory which explains how emulsifying agents reduce interfacial tension between immiscible liquids. Explore the forces involved in forming emulsions.