Topologically reconfigurable nematic emulsions.

In emulsions of multicomponent fluids, the dispersed phase forms tiny droplets in the continuous phase. In situ control and manipulation to achieve diversity in emulsion droplets for emerging applications is challenging. In a liquid crystal-based emulsion, the surface anchoring of the molecules at the isotropic fluid-liquid crystal interface introduces elastic distortions that result in anisotropic interparticle interactions, similar to electrostatic interactions between multipoles, which also lends a naming analogy as elastic dipoles, quadrupoles, and higher. However, controlling the anchoring condition at the interface at will is rarely achieved. Here, we present an emulsion system in which silicone oil droplets in a nematic liquid crystal spontaneously induce conic surface anchoring, forming elastic hexadecapoles without any surfactant. The conic degenerate surface anchoring shows continuous reversible anchoring transition to tangential and homeotropic below and above the ambient temperature, respectively. We introduce a physical design principle and in situ control to achieve three-phase compound droplets with diverse morphologies and topologies by fusing elastic hexadecapoles of oil droplets with elastic dipoles of glycerol droplets. The surrounding director field and the resulting defect structure of the compound droplets are analyzed by numerical simulations. Our approach to forming compound droplets will allow the on-demand design of building blocks for engineered emulsions for reconfigurable composite materials.