Comparison of structural and mechanical properties between water-in-oil high internal phase Pickering emulsions stabilized with surface-modified spindle-shaped and amorphous TiO2 particles

Water-in-oil high internal phase Pickering emulsions (W/O HIPPEs) are known for their polyhedral droplet structures and viscoelastic properties, attributed to their high dispersed phase volume fraction. These emulsions are particularly useful for encapsulating water-soluble compounds while minimizing the use of the oil phase, making them highly desirable for applications in industries such as pharmaceuticals, cosmetics, and food. While most studies have focused on stabilizing oil-in-water (O/W) HIPPEs using amorphous TiO₂ particles, this study, for the first time, investigates the stabilization of W/O HIPPEs using TiO₂ particles modified with hydrophobic stearic acid to enhance stability. Additionally, we explore the critical role of particle shape—comparing spindle-shaped and amorphous particles—on the interfacial stability and mechanical properties of W/O HIPPEs. Through detailed analysis of droplet size, particle behavior at the interface, and the rheological properties of the emulsions, we demonstrate the versatility of these TiO₂ particles in stabilizing HIPPEs with tunable internal structures. This research provides a foundation for the customizable design of HIPPE formulations, paving the way for targeted applications across a wide range of industries.