Surface Nanopatterning Using the Self-Assembly of Linear Polymers on Surfaces after Solvent Evaporation

The morphology of linear polybutadiene physisorbed on freshly cleaved mica from a dilute polymer solution is investigated through atomic force microscopy. A fine-structure study shows that the monolayer morphology in air (after rapid solvent evaporation) depends strongly on the molecular weight ( M w ) of the linear polymer, the adsorbed amount, and the conformation adopted by the adsorbed polymer chains under good solvent conditions. The dependence of the observed polymer structure on M w is most significant for samples with high surface density, where the intermolecular interactions among the adsorbed polymers are important. For high surface density, the adsorbed polymers tend to aggregate and minimize unfavorable contacts with air for all of the different M w samples, leading to an isotropic structural pattern. These structural phenomena with increasing surface density are explained on the basis of the intermolecular interactions of the adsorbed polymers under good solvent conditions, and after the abrupt solvent evaporation corresponding to poor solvent conditions. The experimental observations are further discussed using the results obtained from molecular dynamics simulations of a simple coarse-grained model.