CAPILLARY CONDENSATION DUE TO VAN-DER-WAALS ATTRACTION IN WET SLITS

Wetting films (of thickness t less than or equal to 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 approximate to 3t 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.