Adsorption isotherms of associating chain molecules from Monte Carlo simulations

The inhomogeneous behaviour of associating chain fluids is studied by molecular simulation. The fluid molecules are modelled as a chain of four tangentially bonded Lennard-Jones spheres with an associating square-well site placed at an end sphere. Adsorption isotherms between a bulk phase and a system confined between two parallel structureless walls are obtained using the Gibbs ensemble Monte Carlo technique. Walls and molecules with and without associating sites, different pore widths and different solid-fluid interactions are considered. For surfaces without associating sites, the adsorption is seen to be governed by the solid-fluid interactions of the molecules rather than by the molecules ability or inability to self-associate. The number density of associating sites placed on the walls strongly influences the adsorption characteristics of these molecules.