Superstabilization and Functionalization of Foams and Emulsions by Particles with Engineered Structure and Properties

We will discuss how particles with anisotropic shape and controlled properties can be synthesized and used in the formation of Pickering foams and emulsions with new functionality. We have designed processes for the large-scale formation of rod-like polymer particles. These rod-like particles act as "superstabilizers" of foams and emulsions by forming rigid adsorption shells around the bubbles or droplets. The superstabilization effect is made possible by rod entanglement, formation of hairy shells, and sustaining of thick water films. Similar long-term stabilization was achieved with irregular particles from hydrophobically modified cellulose (HMC), formed by a water-only pH-jump precipitation process. Such particles can also be used to enrich the Pickering foams and emulsions with additional features such as color, specific rheological response, stability against drying and controlled release of components. We will discuss how the addition of pH-sensitive dyes during the process of formation of HMC particles leads to co-precipitation and strong adsorption of the dyes on the cellulose particle surfaces. These strongly colored HMC particles act not only as strong stabilizers of the foams, but also allow their intense and selective coloration without any coloring of the solution medium. The results illustrate how particle stabilizers can be used to make dispersion systems of unusual properties.