Aqueous foams stabilized by hexylamine-modified Laponite particles

Stable foams have been generated in low concentration aqueous dispersions of hexylamine-modified Laponite particles. The particles are of primary size 30 nm, modified with hexylamine molecules to render them partially hydrophobic or moderate flocculants. Infrared adsorption spectra and zeta potential measurements confirm the adsorption of hexylamine molecules on the Laponite particles. The foamability, drainage behavior and microstructure of wet foams were studied in terms of their dependence on the content of Laponite particles and the concentration of hexylamine. Laser-induced confocal microscopy observations confirm that stable bubbles appear to be surrounded by a thin layer of hexylamine-modified Laponite particles, which is crucial to the stability of foams. The interfacial rheology of the same systems has been also investigated by measuring the dilational viscoelasticity as a function of hexylamine concentrations. The adsorption of particles at the air-water interface has the effect of increasing dilational surface elasticity, indicating that the gel-like layer at the interface inhibits foam drainage and bubble coalescence.