Adsorption of End-Functionalized Polystyrene on Model Textured Surfaces

Adsorption of iminium ion end-functionalized polystyrene on model rough surfaces has been investigated. The model surfaces were prepared by spin coating a solution of colloidal silica beads on aluminumcoated silicon surfaces. Atomic force microscopy and scanning electron microscopy of the surfaces revealed a nearly hexagonal packing of beads. Static secondary ion mass spectroscopy and X-ray photoelectron spectroscopy have been used to measure relative changes in the adsorbed amounts on the model surfaces compared to a flat surface. We observe a significant enhancement of adsorption when the bead to polymer radius (ρ/R_g) is of order unity. For ρ/R_g ≫1, the adsorbed amounts approach that on the smooth surfaces, whereas for ρ/R_g< 1, the adsorption is substantially reduced. The enhancement in adsorption is interpreted as a favorable reduction in crowding or stretching energy on adsorption, whereas the reduction is understood in terms of topologically induced steric hindrance to adsorption.