THIN LIQUID-FILM STRUCTURE AND STABILITY - THE ROLE OF DEPLETION AND SURFACE-INDUCED STRUCTURAL FORCES

Film stability and structure formation inside a liquid film containing colloidal particles are investigated by Monte Carlo (MC) numerical si mulations and by analytical methods. The effective pair interaction be tween particles is calculated from the Ornstein-Zernike theory with Pe rcus-Yevick closure. Consistent with the recent experimental observati ons and theoretical studies, these MC simulations reveal the phenomena of internal particle layering as well as inlayer structure formation. In particular, an ordered two-dimensional hexagonal structure is obse rved at a particle concentration of 37 vol% (instead of 43 vol% for th e hard-sphere potential) when the effective pair interaction between p articles is taken into account. Furthermore, the particles inside a la yer ''condense'' due to the attractive depletion force which leads to the formation of voids. The formation of such void structures results in the formation of ''dark spots'' which have been observed in film th inning experiments. The calculated film structural disjoining pressure , created by the particles inside the film, is found to be in agreemen t with the experimentally measured force-distance curves using the sur face force apparatus. (C) 1995 American Institute of Physics.