Selective emulsion inversion in an equilibrium Janus drop. 1. Unlimited space

Area of Science:

• Colloid and Surface Science
• Materials Science

Background:

• Janus emulsions, with distinct properties on each hemisphere, are crucial in advanced materials.
• Understanding their stability and phase inversion is key for controlling emulsion behavior.

Purpose of the Study:

• To investigate the conditions leading to catastrophic phase inversion in a single Janus emulsion drop.
• To analyze the structural transformation of Janus drops under varying oil and water phase volumes.

Main Methods:

• Utilized local equilibrium calculations to model a single Janus drop composed of two immiscible oils (O1, O2) in an aqueous continuous phase.
• Systematically varied the relative volume of O2 (lower interfacial tension) while maintaining the O1 radius constant.
• Calculated the limiting coverage of O1 by O2 and simulated phase inversion by reducing the aqueous phase volume.

Main Results:

• Determined the limiting fraction of O1 covered by O2 for infinite O2 volume.
• Demonstrated selective emulsion inversion from (O1+O2)/W to (W+O1)/O2 upon reduction of the continuous aqueous phase volume.
• Observed subsequent reduction in the size and radius of the water cap with further water removal.

Conclusions:

• Catastrophic inversion of Janus emulsion drops is achievable by manipulating phase volumes and interfacial tensions.
• The study provides a predictive framework for controlling Janus emulsion morphology and stability.