Temperature‐Responsive Janus Particles as Microsurfactants for On‐Demand Coalescence of Emulsions

A new strategy that utilizes temperature‐responsive wax‐based Janus particles as microsurfactants to simultaneously achieve enhanced emulsion stability, as well as, on‐demand coalescence of emulsion droplets is presented. The dumbbell structure with different surface wetting properties on each side of the Janus particle enables the particles to strongly adsorb at the liquid–liquid interface, leading to excellent stability against coalescence for both water‐in‐oil (W/O) and oil‐in‐water (O/W) emulsions. Moreover, these Janus microparticles are composed of a hydrophilic acrylate resin and a hydrophobic wax compartment which transitions from a frozen to an oil‐soluble molten state above the melting point. This allows the particle‐adsorbed droplets to coalesce above a designated temperature, depending on the type of wax material used. It is envisioned that the excellent emulsion stability and the tunable and rapid response to local temperature enabled by the wax‐based Janus particle offers new and exciting opportunities in the advancing technologies including micro‐reactors and drug delivery systems to name a few. Wax‐based Janus particles with dumbbell structures are prepared to simultaneously achieve enhanced emulsion stability and tunable thermal coalescence of these Janus particle‐stabilized emulsion droplets. The amphiphilic nature and the structural advantages of the Janus particles offer enhanced stability for both water‐in‐oil and oil‐in‐water emulsions while the thermo‐responsive nature of wax enables these particle‐stabilized droplets to coalesce above a designated temperature.