Ordering of hydrophilic and hydrophobized silica particles
Prof. Dr. Regine von Klitzing (Technische Universität Darmstadt)

The presentation addresses ordering phenomena of Silica suspensions under confinement in a Colloidal Probe AFM (CP-AFM). The wavelength λ scales with the particle number density as λ=ρ-1/3. An extrapolation towards high volume fractions shows that the ρ-1/3 scaling law for λ ends up into a cubic lattice found for one-component systems like organic solvents, where λ=d (d: diameter of molecules, particles etc.). A deviation from the exponentially decaying cosine function was found and can be described by an additional repulsion term [2,3] which will be discussed. Furthermore, it will be shown how oscillatory forces can be switched on and off by external stimuli [4].
Partially hydrophobized Silica particles order laterally at the interfaces of a free-standing film. They can form percolation networks which seem to stabilize foam films and even foams, i.e. so called Pickering foams