Nonspherical Particle Stabilized Emulsions Formed through Destabilization and Arrested Coalescence

Area of Science:

• Colloid and Surface Science
• Materials Chemistry
• Emulsion Technology

Background:

• Sphericity of emulsion droplets is driven by interfacial tension, requiring methods to overcome this for nonspherical shapes.
• Interfacial particle jamming is a known method, but precise control over particle coverage is crucial.
• Existing methods for creating nonspherical emulsions often lack scalability or precise control.

Purpose of the Study:

• To develop a scalable, novel batch process for producing nonspherical particle-stabilized emulsions.
• To investigate the simultaneous formation of interfacially active particles and accelerated emulsion destabilization.
• To understand the role of particle formation, electrolyte addition, and shear in controlling droplet morphology.

Main Methods:

• Utilized surfactant-stabilized oil-in-water emulsions with dopamine.
• Introduced tris(hydroxymethyl)aminomethane hydrochloride buffer to initiate dopamine polymerization and reduce Debye length, promoting coalescence.
• Employed pendent drop tensiometry and interfacial shear rheology to study interfacial behavior under varying buffer concentrations and shear rates.
• Demonstrated efficacy with a secondary system using sodium dodecyl sulfate and polypyrrole particles.

Main Results:

• Polydopamine nanoparticles formed in the continuous phase adsorbed to the interface during coalescence, leading to anisotropic droplets via arrested coalescence.
• Higher shear rates accelerated coalescence and secondary droplet formation.
• Lower shear rates resulted in thicker interfacial films.
• The process successfully generated nonspherical droplets in both dopamine/polydopamine and SDS/polypyrrole systems under optimized conditions.

Conclusions:

• The developed batch process offers a scalable route to nonspherical particle-stabilized emulsions.
• Arrested coalescence, driven by in-situ particle formation and electrolyte-induced destabilization, is key to achieving anisotropic droplet shapes.
• System parameters like buffer concentration and shear rate allow for control over interfacial properties and droplet morphology.