Batch-Scale Preparation of Reverse Janus Emulsions

A strategy is proposed to produce novel (W1 + W2)/O reverse Janus emulsions in batch scale simply by one-step vortex mixing. Aqueous two-phase systems (ATPSs), i.e., two immiscible aqueous phases dominated by sodium carbonate and ethanol, respectively, are employed as inner phases and vegetable oil (VO) as continuous phase. The geometry of the Janus droplets, although formed as a result of a kinetic process, is tunable and controllable easily by adjusting the composition of ATPSs based on three-phase diagram. Reducing the relatively higher water/oil interfacial tensions to a comparable value of water/water interface, which is extremely low in order of 0.1 mN/m, is achieved by employing a fluorocarbon surfactant. Moreover, the weak acid-induced deprotonation of the fatty acid in the VO phase due to the presence of sodium carbonate also contributes to the lower water/oil interfacial tension. The total free-energy values calculated verify the overwhelmingly favored Janus geometry, which indicates that this topology is heavily preformed as local equilibrium state. The approach proposed provides vehicle for the synthesis of aqueous-based materials with various advanced morphologies.