Nonspherical\nParticle Stabilized Emulsions Formed\nthrough Destabilization and Arrested Coalescence

To form nonspherical emulsion droplets, the interfacial\ntension\ndriving droplet sphericity must be overcome. This can be achieved\nthrough interfacial particle jamming; however, careful control of\nparticle coverage is required. In this work, we present a scalable\nnovel batch process to form nonspherical particle-stabilized emulsions.\nThis is achieved by concurrently forming interfacially active particles\nand drastically accelerating emulsion destabilization through addition\nof electrolyte. To achieve this, surfactant-stabilized oil-in-water\nemulsions in the presence of dopamine were first produced. These emulsions\nwere then treated with tris(hydroxymethyl)aminomethane hydrochloride\nbuffer to both simultaneously initiate polymerization of dopamine\nin the emulsion continuous phase and reduce the Debye length of the\nsystem, thus accelerating droplet coalescence while forming surface-active\nparticles. The concentration of buffer and imposed shear was then\nsystematically varied, and the behavior at the interface was studied\nusing pendent drop tensiometry and interfacial shear rheology. It\nwas found that polydopamine nanoparticles formed in the emulsion continuous\nphase adsorbed to the reducing interface during coalescence, resulting\nin anisotropic droplets formed via arrested coalescence. Greater shear\nrates resulted in accelerated coalescence and formation of secondary\ndroplets, whereas lower shear rates resulted in thicker interfacial\nfilms. The efficacy of this method was further demonstrated with a\nsecond system consisting of sodium dodecyl sulfate as the surfactant\nand polypyrrole particles, which also resulted in nonspherical droplets\nfor optimized conditions.