Ionic liquid forms nanoscale emulsions with no added surfactant

Sydney-led researchers show an amphiphilic ionic liquid can structure microemulsions on its own, pointing to fewer surfactant residues in products.

An international team led by the University of Sydney has shown a way to make microemulsions without conventional surfactants. The work was published in 2026 in the Journal of the American Chemical Society, with Dr. Haihui Joy Jiang as first author.

The team used an ionic liquid, propylammonium nitrate (PAN), which is amphiphilic, meaning it has both water-loving and oil-loving character. They compared it with ethanolammonium nitrate, a related ionic liquid that is polar but not amphiphilic. Using high-resolution X-ray scattering and neutron scattering, including isotopic labeling, they probed the structure. Some neutron work ran on the Quokka instrument at ANSTO. In a mixture of water, PAN and octanol, they found three distinct environments: a polar region rich in water and PAN, a nonpolar region of octanol hydrocarbon chains, and an interface of PAN and the polar ends of octanol. In mixtures that split into two phases, polar and nonpolar components were very unevenly distributed, which may matter for liquid-liquid separation.

Microemulsions have structures a few billionths of a meter across. They are used in pharmaceuticals, food, chemical processing and nanomaterial manufacture. Conventional surfactants add cost, raise environmental concerns, carry potential toxicity and are hard to remove from finished products. If amphiphilicity in the liquid itself can do the structuring, one ingredient class that is costly and hard to strip out could be reduced.

The caveats are real. This is fundamental structural work on specific mixtures, mainly PAN with water and octanol. Uses in drugs, food and separation are suggested, not demonstrated, and nothing here shows a product or process ready for use. Watch for tests with other liquid pairs and for any trial in real formulations.

Source: Phys.org