Adsorption and self-assembly of linear polymers on surfaces: a computer simulation study

The adsorption and self-assembly of linear polymers on smooth surfaces are studied using coarse-grained, bead-spring molecular models and Langevin dynamics computer simulations. The aim is to gain insight on atomic-force microscopy images of polymer films on mica surfaces, adsorbed from dilute solution following a good-solvent to bad-solvent quenching procedure. Under certain experimental conditions, a bimodal cluster distribution is observed. It is demonstrated that this type of distribution can be reproduced in the simulations, and rationalized on the basis of the polymer structures prior to the quench, i.e., while in good-solvent conditions. Other types of cluster distribution are described and explained. Measurements of the fraction of monomers bound to the surface, the film height, and the radius of gyration of an adsorbed polymer chain are also presented, and the trends in these properties are rationalized. In addition to providing insight into experimental observations, the simulation results support a number of predicted scaling laws such as the decay of the monomer density as a function of distance from the surface, and scaling of the film height with the strength of the polymer-surface interactions.