Relationship between rheological properties and one-step W/O/W multiple emulsion formation.

Area of Science:

• Colloid and Surface Science
• Materials Science
• Physical Chemistry

Background:

• Normal water-in-oil-in-water (W/O/W) multiple emulsions can be formed via a one-step method.
• This process involves simultaneous catastrophic and transitional phase inversion.
• Critical parameters include emulsification temperature, surfactant blend, and phase ratios.

Purpose of the Study:

• To investigate the physicochemical properties of W/O/W emulsions.
• To gain a mechanistic understanding of their formation.
• To correlate rheological properties with critical formulation and processing parameters.

Main Methods:

• Investigated bulk, surface, and interfacial rheological properties of nonionic surfactant films (CremophorRH40 and Span80).
• Studied these properties under conditions affecting W/O/W emulsion formation.
• Analyzed surfactant behavior in oil and water phases, and at interfaces.

Main Results:

• CremophorRH40 exhibits higher mobility in oil than water, with a phase transition around 78°C.
• Canola oil significantly impacts surface activity, influencing interfacial elasticity.
• Optimal W/O/W emulsion formation correlates with high interfacial shear elasticity and viscosity when surfactants are added to the oil phase.

Conclusions:

• One-step W/O/W emulsions form via simultaneous phase transitions in the Winsor III region.
• Surfactant desorption with increasing temperature indicates phase formation.
• Understanding rheological properties is crucial for controlling W/O/W emulsion formation and stability.