Small-angle scattering characterization of n-aliphatic alcohol films adsorbed on hydroxyled porous silicas

The thickness of a film deposited on a porous sample can be determined by comparing the tail behaviour of the relevant small-angle scattering intensity with that predicted on the basis of some theoretical models of the film structure. A critical comparison of the present models is reported. The model depicting the film as a third homogeneous phase of the coated sample is the most predictive one because it allows us to determine also the surface area per coating molecule. This conclusion is checked by analyzing the small-angle scattering intensities of a set of samples obtained by coating, via an evaporative technique, a hydroxyled silica gel with different amounts of octadecanol or dodecanol.