(141g) Associating Colloids and Active Surfaces; A Density Functional Theory Approach with Multi-Body Correlations

Predicting the thermodynamic properties and self-assembly of patchy colloids and of hydrogen bonding molecules (e.g., hydrogen fluoride and water) continues to be a challenge of statistical mechanics based theories. The most commonly applied approach is Wertheimâ??s perturbation theory and its extensions for associating particles. The first order limit of this theory treats associating sites independently and assumes each site can form only one bond. This approach allows for the development of a very general equation of state for associating molecules in homogeneous (SAFT) and inhomogeneous systems (iSAFT) with any number of association sites. However, in case of large associating sites, the assumption of only bond per site is not accurate anymore. Therefore, a higher order theory is needed to take such effect into account. Here we apply Wertheimâ??s thermodynamic perturbation theory beyond first order for a patchy colloidal fluid near a hard wall with active sites on its surface using a density functional theory approach where the sites on colloids or wall can be large enough to form two bonds, simultaneously. The effect of steric hindrance between two associating species bonded to a third site is included, and the equation of state derived for this system is dependent on the angular size of the sites. To verify the theory predictions, new Monte Carlo simulations have been performed. The theory predictions for distribution of associated species near the hard wall as a function of the size of the sites are in a good agreement with MC simulation.