Lattice Monte Carlo simulation of polymer adsorption at an interface, 2 - Polydisperse polymer

Competitive adsorption of polydisperse polymers at a solid-liquid interface is studied by Monte Carlo simulation (MC). The dynamic process of adsorption prior to equilibrium is traced. Changing fractionation is observed during the process of adsorption. Shorter chains are preferentially adsorbed due to the quick diffusion onto the interface at the beginning stage. However, the preadsorbed shorter chains are gradually displaced by the longer chains to enhance the stabilization of the system. At equilibrium, the distributions total segment density and different adsorption configurations including trains, loops and tails are calculated. Segment fractions of polymers, both adsorbed and in solution, are also estimated. Comparisons with those predicted from Scheutjens-Fleer theory are further investigated. In contrast to monodisperse polymer adsorption, relatively large discrepancies are found between theoretical predictions and MC results in this mixed-polymer adsorption case.