Ionic liquid-in-water emulsions stabilized by molecular and polymeric surfactants


Ionic liquids have drawn notable attention for their unique solvent properties and use in applications like batteries and chemical separations. While many ionic liquids are water soluble, there are numerous examples of ionic liquids that are sufficiently hydrophobic to remain phase separated from water. However, relatively little is known about the stability and properties of ionic liquid-in-water emulsions. Here, we survey a series of ionic liquid-in-water emulsions stabilized by a range of ionic and nonionic molecular surfactants and polymers. To assess droplet stability and dynamics, we characterize the ionic liquid-surfactant interfacial tension, describe qualitative coarsening rates, and quantify droplet solubilization rate. In some instances, we observe unexpected spontaneous formation of complex double and triple emulsions. Our observations highlight approaches for ionic liquid emulsion formulation and provide insight into how to address challenges surrounding stabilization of ionic liquid-in-water droplets with molecular surfactants.


Supplementary material

Video S1
Video S1: Formation of IL/W/IL/W triple emulsion droplet from double emulsion. The IL is [P6,6,6,14][(iC8)2PO2] while the surfactant solution is 5 wt% SDS (sodium dodecyl sulfate). The process involves the sudden emergence of many droplets in the droplet-internal aqueous phase, which then coalesce into a single inner IL droplet. Speed, 1x. Scale, 50 μm.
Methods, supporting figures, supporting table