Uniform, convex structuring of polymeric colloids via site-selected swelling

Non-spherical, polymeric colloids serve as building blocks for advanced functional materials. We propose a novel method to produce morphologically controlled, non-spherical particles by generating site-selected, convex structures on polystyrene (PS) particles. It consists of two simple procedures: a monolayer of PS particles is illuminated with UV light and is subsequently immersed in a fluorinated solvent (HFIP). UV irradiation generates site-selected, oxidized domains on PS particles with a different solvent affinity than unoxidized PS, and HFIP immersion preferentially swells the oxidized domains. Such swelling gives rise to site-selected, convex structures on PS particles. By adjusting UV irradiation conditions, including incident and azimuth angles, the oxidized sites, i.e., the swelled portions, can be accurately situated, allowing us to produce various convex shapes, including chiral shapes at desired positions on PS particles.