General Route toward Chemically Anisotropic Colloids

We report a versatile emulsion-based synthesis for the preparation of nanometer-sized dumbbell-shaped particles that contain two chemically different patches. One patch consists of solely polystyrene and is therefore chemically inert toward most chemical reactions. The other patch contains reactive surface chlorine groups. To achieve this, we prepared seed particles with a chlorinated surface that were transformed into dumbbell-shaped particles by introducing a liquid styrene protrusion on the surface, which was polymerized to form a solid, anisotropic colloidal particle. The chlorinated layer on the seed particles provides both sufficient hydrophilicity to set a finite contact angle between the liquid protrusion and the seed particle and a chemical handle for further site-specific modification of the reactive patch. The chlorine groups can be easily converted to other functionalities, making these particles an ideal platform for the preparation of colloids with complex (surface) properties. As an example, it was shown that this patch could participate in copper-catalyzed Huisgen 1,3-dipolar cycloaddition reactions after conversion of the chlorines to azides. This very robust form of click chemistry allows us to decorate the reactive patch with a wide variety of molecules.