Emulsion Engineering: Polymer-mediated Hierarchical and Reversible Emulsion Droplet Assembly

摘要

Emulsions - the dispersion of one liquid throughout another,immiscible liquid - are important materials in both commercial products and processes and in academic research. Emulsion droplet stability is often achieved using small molecule surfactants; however these are rarely kinetically stable towards droplet coalescence over prolonged periods.1 In contrast,colloidal particles can produce very stable emulsions due to their strong,often irreversible,adhesion at the droplet surface.1 Responsive colloids - that is,colloids whose surface hydrophobicity can respond to external stimuli - have recently been employed as "advanced" surfactants.2 In many instances,emulsions stabilised with responsive colloids can be demulsified - that is,phase- separated - on-demand by simply changing solution pH. Herein we present a new class of responsive polymeric emulsifier which produces stable droplets with controllable surface functionality. From these 'building blocks' we are able to assemble a range of unique macroscopic,robust,liquid-like structures with a high degree of control and uniformity. We refer to these assembled droplets as engineered emulsions. Since the polymeric surfactants are responsive,the engineered emulsions can be disassembled back into free-flowing conventional droplet dispersions on changing the solution pH.