MOLECULAR NETWORKS IN THE SPREADING OF MICRODROPLETS

We report here an experimental investigation of the spreading of OH-terminated poly(dimethylsiloxane) droplets on bare and on modified silica. On bare silica, droplets take a remarkable shape, with a shoulder at a thickness corresponding to the gyration radius of the molecules. The effect disappears if the surface is made hydrophobic. We interpret these features as being due to the formation of a network of molecules anchored onto the solid. For weak anchoring sites, the spreading goes on through the network. If strong anchoring sites are available, the spreading of microscopic droplets eventually stops.