X-ray reflectivity provides evidence of hydrophobic gap at buried water-polymer interface

A group at the Max Planck Institute led by Professor H. Dosch recently performed detailed studies on the gap between water and a water-repelling surface. Silicon wafers, functionalized by a self-assembled monolayer of octadecyl-trichlorosilane (OTS), provide strongly hydrophobic substrates. The main interest here is what happens when water comes onto the OTS layer. The experiment was not easy, because the liquid water-solid interface is deeply buried in this case. In this research, X-ray reflectivity measurements using an unusually high-energy beam (72.5 keV) were carried out. The results indicate the existence of a hydrophobic gap on a molecular scale at the solid-water interface. For more information, see the paper, "High-resolution in situ X-ray study of the hydrophobic gap at the water-octadecyl-trichlorosilane interface", M. Mezger et al., Proc. Natl. Acad. Sci. USA, published online before print November 20, 2006