Highly Persistent and Robust Emulsion Stabilized by Hierarchical Cellulose Microgel through Stereo-hindrance under Extreme Conditions

Emulsion stabilization oil-in-water under harsh conditions (e.g., hypersaline, acid and alkali, and high temperature) is a great challenge for conventional emulsion stabilizers, including surfactants or particles. Herein, a persistent and robust emulsion under harsh conditions is achieved via a sustainable solution based on a hierarchical cellulose microgel (h-CMG). h-CMG in aqueous suspension establishes stable 3D networks by its nanotentacles and microbody, which can spatially hinder the approach and coalescence of droplets to each other and stabilize the emulsion. Unlike the emulsion stabilized by minimizing the interfacial energy and protecting the water/oil interface, the emulsion spatially stabilized by h-CMG exhibits extensive tolerance to extreme conditions and the feature of stable high internal phase emulsion (80%, v/v). The related droplet size and emulsion volume are almost unchanged in the pH range of 1 to 14, in NaCl aqueous solution of 2 mol/L, or even at 80 °C for 12 h. This genuine biobased emulsifier is highly favorable to the food, cosmetics, and pharmaceutical industries without the risk of nanotoxicity, and it also can provide a reliable emulsifier for the chemical and drilling industries involving harsh operation circumstances.