This paper summarizes recent experimental and theoretical research conducted in our laboratories on understanding the properties of colloidal suspensions confined to a film. The results of statistical mechanics modelling to explain some experiments on thinning liquid films formed from concentrated mono-and bidisperse colloidal suspensions are reported. The effect of colloidal particle size bidispersity on the local density distribution and film stability is discussed in detail.

Single-particle time correlation function F s (k, t) of pure fluids is studied within the generalized mode approach. Analytical expression for self-intermediate scattering function, which contains oscillating terms, is obtained for three-variable basis set of single-particle dynamic variables. The meaning of oscillating contributions is discussed, and it is shown, that in lowdensity fluids the oscillating contributions do not appear. Our approach, developed within the five-variable scheme, is used for the analysis of MDderived single-particle time correlation function of Lennard-Jones fluid at two densities. It is shown, that the proposed scheme allows us to reproduce perfectly the function F s (k, t) at the whole range of wavenumbers k studied. The generalized self-diffusion coefficient as a function of k is also calculated.

The equivalence of the asymptotic expression for the interaction energy between a pair of large hard spheres in a fluid of small hard spheres that has been obtained by Roth et al. [Phys. Rev. E, 2000, vol. 62, p. 5360] using Fourier transforms and an expression that we have obtained [J. Colloid Int. Sci., 1999, vol. 210, p. 320] using Laplace transforms is pointed out and commented upon.

Molecular dynamics (MD) simulations are reported for a Lennard-Jones fluid adsorbed into a model silica gel to study the dynamic properties of the adsorbed methane molecules. The mean-square displacement and velocity autocorrelation function of the adsorbed molecules are calculated for a set of supercritical temperatures at low (gas-like) and high (liquid-like) fluid densities and compared with the same data for a bulk fluid. The evaluated radial distribution functions illustrate the formation of a contact layer on the pore surface that is consistent with the decrease in the mobility of the adsorbed molecules in a porous environment. The calculated self-diffusion coefficient indicates a good quantitative agreement with the measured data for methane confined to the silica gel.

Monte Carlo simulation studies are performed for the Lennard-Jones-like two Yukawa (LJ2Y) potential to show how properties of this model fluid depend on the replacement of soft repulsion by hard-core repulsion. Different distances for the positioning of hard-core have been explored. We have found that for temperatures slightly lower and slightly higher than the critical point temperature for the Lennard-Jones fluid, the placement of the hard-core at distances shorter than zero-potential energy is well justified by thermodynamic properties that are practically the same as in the original LJ2Y model without hard-core. However, going to extreme conditions with the high temperature one should be careful since the presence of the hard-core provokes changes in the properties of the system. The later is extremely important when the mean-spherical approximation (MSA) theory is applied to the treatment of the Lennard-Jones-like fluid.