This technology relates to synthesizing nanoparticles with multiple polymer assemblies attached. In one example, a first anchoring compound is attached to a nanoparticle, and a first group of monomers are polymerized on the first anchoring compound to form a first polymeric chain covalently bonded to the nanoparticle via the first anchoring compound. In another example, a first polymeric chain can be attached to the nanoparticle, where the first polymeric chain has been polymerized prior to attachment to the nanoparticle. Thereafter, a second anchoring compound is attached to the nanoparticle, and a second group monomers are polymerized on the second anchoring compound to form a second polymeric chain covalently bonded to the nanoparticle via the second anchoring compound.