Construction of Nano-Janus emulsion by phase inversion composition.

[Display omitted] • The construction of the complex droplets with precisely internal structures is simply by titration water at room temperature and gentle stirring. • The noteworthy achievement is reached by the success formation of a four-component lamellar liquid crystal with two immiscible oils, in addition to water and surfactant. • The precise modulation of the advanced structure of the nano Janus emulsion. • The composition diversity of the liquid crystal provides additional freedom for structural regulation, i.e. from "crescent", "half-moon", to "moon with a hole". Nano-Janus emulsion possesses excellent solubilization capabilities of both aqueous and organic materials, various liquid–liquid interfaces, and precisely controllable morphology. Successful construction of nano Janus droplets at mild conditions of room temperature and low-energy input will expand the industrial application. Two immiscible liquids of silicone oil (SO) and oleic acid (OA) are used as internal phases, and water is added dropwise at mild temperature. The topology of the nano-sized complex droplets is characterized by cryo-TEM, SAXS, and FF-TEM. Micro structure of lamellar liquid crystal (Lα), which is the critical transition phase, is investigated to reveal the formation mechanism. Topology adjustment including size range, volume ratio, and interface curvature is investigated. Complex nano droplets with snowman shape are successfully constructed in batch-scale at mild temperature of 30 °C and water-dripping rate of 1.0 mL/h. Formation of a four-component Lα phase is the critical point to the successful construction of the nano-Janus emulsion, which also creates additional freedom for structural regulation. The size of the complex droplets is freely alternated in the range of 50–500 nm and the morphology of one lobe is controlled from "crescent" to "half-moon", and "moon with a hole". [ABSTRACT FROM AUTHOR]