Surfactant Partitioning in Nanoemulsions

Area of Science:

• Colloid and Surface Science
• Materials Science
• Chemical Engineering

Background:

• Nanoemulsions (NEMs) possess high surface area-to-volume ratios, influencing interfacial phenomena.
• Understanding surfactant behavior is crucial for controlling nanoemulsion properties and stability.
• Fractionated NEMs offer a unique system for studying interfacial adsorption.

Purpose of the Study:

• To investigate surfactant partitioning between bulk and interfacial phases in silicone oil nanoemulsions.
• To develop an accurate adsorption isotherm for sodium dodecyl sulfate (SDS) on nanodroplet interfaces.
• To model surfactant concentration changes after high-flow-rate emulsification (HFRE).

Main Methods:

• Utilized gravimetric and electrical conductivity methods to measure bulk and surface surfactant concentrations.
• Employed the du Noüy ring method to determine macroscopic interfacial tension (IFT).
• Developed a model to predict final bulk surfactant concentration post-HFRE.

Main Results:

• Obtained a raw adsorption isotherm for SDS, which was adjusted using IFT measurements.
• The adjusted isotherm was successfully described by a Langmuir equation.
• Demonstrated significant surfactant partitioning to interfaces after HFRE, validating the predictive model.

Conclusions:

• The Langmuir equation effectively models SDS adsorption on silicone oil nanodroplet interfaces.
• Surfactant partitioning is a critical factor in nanoemulsion formation via HFRE.
• The developed model accurately predicts surfactant concentration trends in polydisperse nanoemulsions post-HFRE.