STUDY OF THE ADSORPTION FROM AQUEOUS-SOLUTION OF HEXAETHYLENE GLYCOL MONODODECYL ETHER ON SILICA SUBSTRATES USING THE TECHNIQUE OF NEUTRON REFLECTION

The adsorbed amount and the structure of layers of hexaethylene glycol monododecyl ether (C12E6) adsorbed on three different silica substrates have been determined by neutron reflectivity. The substrates studied were amorphous silica, crystal quartz, and the oxide layer on a silicon crystal. The characteristics of the substrates, in particular surface roughness, were determined prior to adsorption. The adsorbed surfactant was found to form a bilayer of overall thickness 49 +/- 4 angstrom, with each bilayer unit occupying an area of 44 +/- 4 angstrom 2, at and above the critical micelle concentration of C12E6 (8.7 x 10(-5) M). The identical model was applied to all substrates, although the coverage varied between 40% and 60% and may be correlated with the surface roughness of the solid substrates.