Particle stabilized foams are an interesting type of dispersion with applications in various fields of technology from mineral processing to the food industry. Nevertheless, the detailed mechanisms of how (nano)particles stabilize foams are not fully resolved, yet.
It has been shown that combining nanoparticles and suitable surfactants can lead to increased foamability and foam stability compared to the surfactant-only system without nanoparticles.
As a model system, we use hydrophilic silica nanoparticles that do not attach to the water/air interface until they are modified with alkylamines which render them hydrophobic, so they become surface active. The particle hydrophobicity was adjusted by varying the amount of adsorbed amine and/or the carbon chain length.
The systems were characterized at various length scales from the nanometer to the centimeter scale. Results from surface pressure isotherms suggest the formation of a colloidal network around the air bubbles, whereby the network density correlates strongly with the foamability. We determine the contact angle of the nanoparticles at the air water interface via x-ray reflectivity. Diffusing wave spectroscopy was used to probe the particles inside the foam as well as the system’s temporal evolution.
