Structure of concentrated nanoemulsions

Area of Science:

• Colloid and Surface Science
• Soft Matter Physics
• Materials Science

Background:

• Nanoemulsions are critical in various applications, requiring precise control over droplet size and interactions.
• Understanding the structural properties of concentrated nanoemulsions is key to predicting their bulk behavior.
• Dispersions of deformable droplets present unique challenges compared to rigid particle systems.

Purpose of the Study:

• To synthesize and characterize well-defined nanoemulsions with uniform, deformable droplets.
• To investigate the structure factor S(q) of concentrated nanoemulsions across a range of volume fractions (0 to 0.6).
• To elucidate the influence of droplet deformability on the emergent glassy structures in these systems.

Main Methods:

• Extreme shear mixing to create silicone oil-in-water nanoemulsions stabilized by sodium dodecyl sulfate.
• Centrifugal size fractionation to obtain nanoemulsions with a narrow size distribution (average radius a=75 nm).
• Small angle neutron scattering (SANS) to measure the structure factor S(q) of concentrated dispersions.

Main Results:

• Nanoemulsions with controlled average droplet size were successfully prepared.
• The structure factor S(q) of concentrated nanoemulsions was determined, showing glassy behavior.
• A deviation from hard sphere predictions was observed: the primary peak height in S(q) exhibited a maximum with increasing volume fraction.
• This deviation was attributed to droplet deformability within the glassy structure, not just polydispersity.

Conclusions:

• Deformable nanoemulsion droplets form glassy structures that differ from hard sphere models.
• Droplet deformability plays a significant role in the structural organization of concentrated nanoemulsions.
• The findings provide insights into the physics of soft matter glasses and emulsion stability.