“…A pressure gradient is applied across the film and the resulting flux through the film is measured. This type of rate measurement is, however, greatly affected by the presence of any small holes in the film; and indeed it was observed (Rose and Quinn, 1968;Gaines and Ward, 1977;Albrecht et al, 1984) that the measured permeability of LB films depended on the thickness, that is, number of layers. In contrast, the sorption method, which we use in this work, requires no pressure differential across the film, and thus has the advantage that measurements are relatively insensitive to the presence of pin holes (Crank and Park, 1968).…”