Probing Interparticle Interaction and Ordering in Silica-Pluronic-Based Solutions and Emulsions by Small-Angle...

Area of Science:

• Colloid and Surface Science
• Materials Science
• Nanotechnology

Background:

• Non-DLVO forces, introduced by nonionic surfactants, significantly alter silica nanosuspension phase behavior.
• Understanding these interactions is crucial for designing advanced nanocomposite materials.

Purpose of the Study:

• To investigate the impact of nonionic surfactants (Pluronics) on the phase behavior of silica nanosuspensions (Ludox® LS).
• To explore the formation of Pickering emulsions and thermoresponsive phase separations.
• To compare findings with larger silica nanoparticles (Ludox® TM).

Main Methods:

• Utilized small-angle X-ray scattering (SAXS) to study nanoparticle ordering at interfaces.
• Employed small-angle neutron scattering (SANS) to detect intermicellar attraction.
• Analyzed the influence of surfactant properties and nanoparticle size.

Main Results:

• Stable oil-in-water Pickering emulsions formed with both Pluronic-coated and bare Ludox® LS nanoparticles.
• Thermoresponsive liquid-liquid phase separations observed due to non-DLVO steric and hydrophobic interactions.
• Higher Pluronic concentration required for interparticle attraction in smaller LS nanoparticles compared to TM counterparts.

Conclusions:

• Silica nanoparticle size and surfactant hydrophilic-lipophilic balance critically determine silica-surfactant nanocomposite phase behavior.
• Non-DLVO forces play a key role in the observed phenomena, offering new avenues for material design.
• Findings provide insights into the self-assembly of charged nanosuspensions.