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Soft Matter and Biological Physics

Eur. Phys. J. E 6, 315-323 (2001)

Adsorption from pure and mixed vapours of n-hexane and n-perfluorohexane

M.M. Kohonen and H.K. Christenson

Department of Applied Mathematics, Research School of Physical Sciences and Engineering, Australian National University, Canberra A.C.T. 0200, Australia


(Received 30 July 2001)

We have used a modified surface force apparatus (SFA) to study adsorption onto mica surfaces from near-saturated vapours of n-hexane and n-perfluorohexane, and mixtures thereof. For relative vapour pressures in the range 0.9-0.998 the films adsorbed from vapours of the pure liquids range in thickness from 1 to 4 nm, in crude agreement with the predictions of non-retarded van der Waals-Lifshitz theory. The observed deviations from theory show a qualitative difference between the two liquids, which may reflect differences in the significance of structural contributions to the disjoining pressure. Under the same experimental conditions, adsorption from vapours of (one-phase) liquid mixtures gives rise to films which are significantly thicker, over a broad range of intermediate compositions, than those adsorbed from the pure vapours, with a broad maximum in thickness observed near the critical composition of the bulk liquid mixture.

68.08.Bc - Wetting.
68.15.+e - Liquid thin films.
64.75.+g - Solubility, segregation, and mixing; phase separation.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001