Glass bead-bead collisions abrade adsorbed soft-shell polymeric nanoparticles leaving footprints

Demonstrated is a new method for stamping nanoscale polymeric patches (footprints) onto surfaces. Cationic core-shell nanoparticles with hard polystyrene (PS) cores and soft poly(n-butyl methacrylate) (PB) shells spontaneously adsorbed on glass beads suspended in water. With mixing, the bead-bead collisions removed the adsorbed polymer particles, leaving PB footprints. The footprint density on the bead surfaces mirrored the initial density of adsorbed nanoparticles. The footprint thicknesses, measured by AFM, were 10–20nm. Our motivation for this research was developing nanoparticles that promoted glass bead flotation (i.e. nanoparticle flotation collectors). Whereas the adsorbed nanoparticles did promote flotation, glass beads coated only with footprints gave poor flotation recoveries in spite of the hydrophobic nature of PB. We propose that footprint-coated spherical bead surfaces are too smooth for efficient bead attachment to air bubbles. Janus particles with one hard PS lobe and a soft PB lobe were more strongly adhering and more effective at promoting bead flotation, presumably because of high bead/nanoparticle adhesion. Beyond the flotation application, footprint formation could be a simple approach to modifying dispersed particle surfaces in a wide range of applications.