The effect of flow on viscoelastic emulsion microstructure.

Area of Science:

• Soft Matter Physics
• Colloid and Surface Chemistry

Background:

• Emulsions are common oil-in-water or water-in-oil mixtures stabilized by surfactants.
• While static emulsion behavior is well-studied, flow-induced microstructural changes are crucial for applications but less understood.
• Attractive interactions significantly influence emulsion phase behavior.

Purpose of the Study:

• To investigate the impact of flow cessation on the microstructure of viscoelastic attractive emulsions.
• To demonstrate how flow can induce distinct emulsion morphologies.
• To highlight the role of attractive interactions in flow-induced structural changes.

Main Methods:

• Low energy emulsification processing to create small-sized emulsions.
• Controlled observation of emulsion microstructure after flow cessation.
• Analysis of viscoelastic properties and droplet filament dynamics.

Main Results:

• Flow cessation leads to buckling and recoiling of viscoelastic droplet filaments.
• Two distinct morphologies emerge: a concentrated nanoemulsion (previously reported) and randomly flocculated droplet clusters.
• Attractive interactions are key to both observed morphologies.

Conclusions:

• Emulsion morphology is highly sensitive to flow dynamics and attractive interactions.
• Flow cessation can reversibly alter emulsion structure, yielding different microstructures.
• The high interfacial area of these flow-generated emulsions is beneficial for applications in upstream operations, microreaction media, and drug delivery.