Dynamics of Polymer Adsorption onto Solid Surfaces in Good Solvent

Sammanfattning: Adsorption dynamics of various types of uncharged homopolymers onto solid surfaces in good solvent have been studied by using a coarse grained bead-spring model. Brownian dynamics simulation has been used to examine the adsorption process for polymers released near an adsorbing surface, and Monte Carlo simulations have been employed to explore equilibrium properties of adsorbed polymers. Two different types of approaches have been pursued: adsorption of single polymers and adsorption from polymer solutions. For single polymers of varying type, the entire adsorption process was examined and characteristic time dependent properties were extracted. Structural rearrangements of the polymers comprising time regimes of several orders of magnitude were identified. Regarding polymer solutions, polymers of varying length, flexibility, and surface attraction were examined for solutions of similar and dissimilar polymer types at different densities. Solutions containing flexible polymers revealed an extension perpendicular to the surface at long times as the surface pressure increases, reducing the adsorbed polymer segment fraction. Systems of rod-like polymers display an additional relaxation mode, prolonging the final stage of the adsorption process due to the formation of nematic structures of polymers on the surface. Finally, the competitive adsorption of mixed polymer systems is characterized by an initial adsorption of both polymer types, followed by a slow exchange at the surface as the preferentially adsorbing polymer type replaces the other one.