Interfacial Structure of Pickering EmulsionsKjersta Larson-Smith and Prof. Danilo Pozzo

University of Washington Chemical Engineering, Seattle WA

• Particle stabilized emulsions (Pickering) form during the processing of organic fluids in the presence of water and solid micro and/or nanoparticles.

• Particles are enriched at the oil-water interface due to a favorable energy of adsorption.

• Stabilization may be electrostatic or can occur through the creation of an elastic shell that prevent drop coalescence.

• Emulsion stability is controlled primarily by the organization of solid particles at the interface.

• Project goals: – Develop an experimental toolbox to probe the interfacial organization of the particles in the emulsion. – Probe interfacial transitions that occur in Pickering emulsions that are subjected to destabilizing freeze-thaw cycles.

Oil

Model Emulsions: Hexadecane stabilized by functionalized gold and silica nanoparticles (4-100 nm)

Small Angle Neutron and X-ray Scattering Electrostatic Stabilization

++

+++

+++

+

++

+

+ ++

+++

++

+++ +

++

++ +

+ ++

++++

+

++

++

++

Electrostatic Stabilization

++

+++

+++

+

++

+

+ ++

+++

++

+++ +

++

++ +

+ ++

++++

+

++

++

++

Electrostatic Stabilization

++

+++

+++

+

++

+

+ ++

+++

++

+++ +

++

++ +

+ ++

++++

+

++

++

++

Steric StabilizationSteric Stabilization

10-2

10-1

100

101

102

103

104

105

106

I(q)

(cm

-1)

10-5

10-4

10-3

10-2

10-1

100

q (Å-1

)

SANS/USANS 16nm SiO2 Pickering Emulsion Model Fit

Water

50 m

Electrostatics dominate nanoparticle stabilized emulsions