Electrostatic Heteroaggregation: Fundamentals and Applications in Interfacial Engineering.

The aggregation of oppositely charged soft materials (particles, surfactants, polyelectrolytes, etc.) that differ in one or more physical or chemical attributes, broadly referred to as electrostatic heteroaggregation, has been an active area of research for several decades now. While electrostatic heteroaggregation (EHA) is relevant to diverse fields such as environmental engineering, food technology, and pharmaceutical formulations, more recently there has been a resurgence to explore various aspects of this phenomenon in the context of interface stabilization and the development of functional materials.

Macroporous Ceramic Monolith from Nanoparticle-Polyelectrolyte-Stabilized Pickering Emulsions.

In this work, we present a simple and scalable approach for fabricating porous ceramic from emulsions stabilized by a binary mixture of oppositely charged nanoparticles and a polyelectrolyte. The electrostatic heteroaggregation is exploited to form weakly charged particle-polyelectrolyte complexes (PPCs) that readily stabilize oil-in-water emulsions. The concentration of surface-active PPCs is varied to obtain Pickering emulsion gels that can be processed and converted into the macroporous ceramic structure.

Semi-batch and continuous production of Pickering emulsion direct contact steam condensation.

We propose a versatile strategy for the production of highly stable water in oil Pickering emulsion by direct contact condensation of steam. In contrast to conventional methods that use mechanical energy for creating drops, the condensation of steam brought in contact with a non-aqueous colloidal dispersion is exploited to produce Pickering emulsions in two modes of operation, namely, semi-batch and continuous. As steam that comes in contact with oil condenses into water drops, the particles adsorb to the interface and thus arrest drop-drop coalescence.

Porous Ceramics via Processable Pickering Emulsion Stabilized by Oppositely Charged Colloids.

We report a method to produce processable Pickering emulsions in which electrostatic heteroaggregation of oppositely charged fumed silica and alumina particles is exploited. The ability of weakly charged heteroaggregates to adsorb to the oil-water interface favors the formation of highly stable emulsions. A control over the microstructure and rheology of the Pickering emulsion is demonstrated by tuning parameters such as composition, pH, and total concentration of particles.