Structure and phase transitions in a network-forming associating Lennard-Jones fluid in a slit-like pore: a density functional approach

A study is reported of adsorption of an associating Lennard-Jones fluid wit h four associative sites per molecule in a slit-like pore. The density dist ribution of particles in the pore and thermodynamics properties are evaluat ed by using a density functional method. It is found that at low temperatur es the fluid exhibits a set of layering transitions, followed by capillary condensation. Transitions are localized by analysing the grand canonical po tential. The density profiles of particles and the distribution of unbound and differently bonded particles demonstrate changes in the structure of th e fluid in the pore along the phase coexistence. The critical temperature i s lower for a confined fluid, compared with the bulk counterpart. However, an increase in the energy of association increases the critical temperature . The envelope of the capillary condensation is narrower than the bulk liqu id-vapour phase diagram. The dependence of the solvation force on the energ y of association and on the bulk density is discussed.