Synthesis of Janus nanoparticles via a combination of the reversible click reaction and "grafting to" strategies.

A critical challenge in nanoparticle functionalization has been the preparation of polymer-grafted asymmetric (Janus) nanoparticles (diameter < 100 nm). We describe a robust and cyclic method involving a reversible click reaction and "grafting to" strategies to synthesize such nanoparticles. Mechanochemistry was used in a protection-deprotection process to separate nanoparticles cleanly that were anchored to larger particles, and the recovered azide-functionalized larger particles could be recycled as face-blocking moieties. With this combination of strategies, we prepared 15 nm silica nanoparticles that were partially functionalized with poly(methyl methacrylate). Additionally, the unique self-assembly behaviors of the resultant Janus nanoparticles were investigated in different solvents at different concentrations.