Abstract
Nanoscale emulsions are essential components in numerous products, ranging from processed foods to novel drug delivery systems. Existing emulsification methods rely either on the breakup of larger droplets or solvent exchange/inversion. Here we report a simple, scalable method of creating nanoscale water-in-oil emulsions by condensing water vapor onto a subcooled oil-surfactant solution. Our technique enables a bottom-up approach to forming small-scale emulsions. Nanoscale water droplets nucleate at the oil/air interface and spontaneously disperse within the oil, due to the spreading dynamics of oil on water. Oil-soluble surfactants stabilize the resulting emulsions. We find that the oil-surfactant concentration controls the spreading behavior of oil on water, as well as the peak size, polydispersity, and stability of the resulting emulsions. Using condensation, we form emulsions with peak radii around 100 nm and polydispersities around 10%. This emulsion formation technique may open different routes to creating emulsions, colloidal systems, and emulsion-based materials.
Highlights
Nanoscale emulsions are essential components in numerous products, ranging from processed foods to novel drug delivery systems
Emulsification techniques may be broadly classified into two categories: high-energy techniques and low-energy techniques
Nanoscale emulsions formed via condensation remain dispersed for months, though dynamic light scattering (DLS) measurements performed after several months reveal that the peak radius and polydispersity may shift slightly over time
Summary
Nanoscale emulsions are essential components in numerous products, ranging from processed foods to novel drug delivery systems. We report a simple, scalable method of creating nanoscale water-in-oil emulsions by condensing water vapor onto a subcooled oil-surfactant solution. We find that the oil-surfactant concentration controls the spreading behavior of oil on water, as well as the peak size, polydispersity, and stability of the resulting emulsions. We present a bottom-up assembly approach to creating nanoscale emulsions that spontaneously separates condensed nanometric water droplets with thin films of oil as they nucleate. To create this bottom-up assembly, we condense nanoscale water droplets onto surfactant-oil mixtures. Nanoscale emulsions formed via condensation remain dispersed for months, though dynamic light scattering (DLS) measurements performed after several months reveal that the peak radius and polydispersity may shift slightly over time
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