Wr. Birch et al., THE MOLECULAR-STRUCTURE OF AUTOPHOBED MONOLAYERS AND PRECURSING FILMSOF A CATIONIC SURFACTANT ON THE SILICON-OXIDE SILICON SURFACE, Colloids and surfaces. A, Physicochemical and engineering aspects, 89(2-3), 1994, pp. 145-155
We have used X-ray and neutron reflectivity to probe autophobed layers
and precursing films of a cationic surfactant on the SiO2/Si surface.
Formed on retraction from solution, the autophobed films are monolaye
rs. In the autophobed film, the polar head group of the surfactant is
coordinated with its counterion in a region near the oxide surface. Th
e layer thickness is about 11 angstrom and the area per molecule is ab
out 50 angstrom-2. The tails of the surfactants are disordered. When c
onnected to the meniscus of a bulk surfactant solution and equilibrate
d with saturated vapor, the autophobed monolayer becomes a precursing
film. The layer swells with water hydrating the polar SiO2 surface and
head groups.