Most classical studies of self-assembly at interfaces are concerned with equilibrium and dynamic processes are rarely studied. Therefore, studies focusing on equilibrium aspects of self-assembly at interfaces are no longer valid for non-equilibrium self-assembly systems with dynamic features. Here, we present a self-assembly system of surfactant/polar oils at immiscible liquid-liquid interfaces, where one phase is in the motion. The necessity of understanding the phase behavior and kinetics for explaining the dynamic or non-equilibrium processes have been identified. The experimental phase behavior of such system is established and the equilibrium phases are characterized using small-angle X-ray scattering. Interestingly, the characteristics of the interfacial layers in motion show a great agreement with the relevant equilibrium phases. Formation of self-assembly at the interface in our system is driven by solubilization of polar oil in the micelles due to the cosurfactancy effect leading to a spherical micelle-to-lamellar phase transition. The relevant theoretical kinetics studies have been established in both static and dynamic systems. In slow dynamical and static systems, the polar oil solubilization rate is dependent on how fast micelles diffuse away from oil/water interface, while in fast dynamical system, the rate-controlling step of solubilization is determined by direct adsorption of oil into the micelles. In dynamic systems, the oils solubilization rate has shown to be proportional to square root of Reynolds number and micelle number, the latter of which affect solubilization rate in static system as well.

Hydrodynamics, kinetics, and thermodynamics of a self-assembly system of surfactant/polar oils at immiscible liquid- liquid interfaces

ACS Fall 2020 Virtual Meeting

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