ADHESION AND SOLVATION FORCES BETWEEN SURFACES IN LIQUIDS STUDIED BY VAPOR-PHASE EXPERIMENTS

We show how solvation forces in liquids can be measured hy studying th e interaction of surfaces in vapor. This is a convenient method of obt aining information on the inner part of the solvation force, where the surfaces are separated by only a few molecular layers. In particular, the pull-off force between mica surfaces in contact in liquids may be determined easily and accurately this way. Results presented for octa methylcyclotetrasiloxane (OMCTS), cyclohexane, and n-pentane are large ly in agreement with published data obtained by measurements in the li quid phase. Contrary to earlier results, the pull-off force (contact a dhesion) is much larger than expected from extrapolation down to conta ct of the minima of the solvation force. The large values (up to 100 m J m-2) of the adhesion in nonpolar liquids illustrate how misleading i t can be to use the Lifshitz theory to predict the contact adhesion of a polar solid.