Magnetic response Janus emulsions stabilized by Mangeto-surfactant

Abstract

Magnetic response emulsions, with regulated motion of droplets by magnetic fields, provide opportunities in system design. Research in Janus emulsion is blooming attributed to excellent multiple chambers, diverse interfaces, and advanced structures. Responsive Janus emulsions are prepared, using two immiscible oils of dimethyl phthalate (DMP)/vegetable oil (VO) and small molecules of magneto-surfactants ([H-G-C16]FeCl4) as stabilizer, in batch-scale by traditional vortex mixing. The composition of emulsion, the concentration of surfactant, and the emulsification energy are applied to control the topology of the structured fluid, and more importantly achieve the quantitative regulation of magnetic response. Janus droplets with clear inner interfaces are successfully constructed solely by magneto-surfactant, and the strategy is universal and even extended to Cerberus emulsions composed of three separated compartments. The magnetic response is visualized by directed moving against gravity and saturated magnetization. The responsivity is enhanced about 44.5%-54.5% accompany with VO lobe transformation from “waxing crescent” to “full moon with a hole”. The magnetic response is increased as high as 80.0% by decreasing the droplet size. Delicate calculations reveal that the ordered arrangement of [H-G-C16]FeCl4 at the interfaces, mainly contributes to the magnetic response compared with aggregates in the continuous phase. The adsorption on the VO/aq interface dominates the overall response due to the higher affinity of the surfactant to the VO phase. The findings open an avenue in the production of magneto-responsive multiple emulsions, which would push forward future application in smart microreactors, intelligent fluids, and responsive delivery systems.