Capillary condensation due to van der Waals attraction in wet slits.

Abstract

Wetting films (of thickness $t\ensuremath{\le}14$ nm) of $t$-butanol in slits of mica have been studied as a function of the slit width $H$. A capillary condensation transition occurs when $H\ensuremath{\approx}3t \mathrm{for} t>5$ nm. This is consistent with a mechanism of film thickening and coalescence due to van der Waals forces across the slit. van der Waals thickening cannot account for the transition with thinner $t<5$ nm) adsorbed films, as found previously with nonwetting liquids.