Self-assembly of soft nanoparticles with tunable patchiness

Details of the forces between nanoparticles determine the ways in which the nanoparticles can self-assemble into larger structures. The use of directed interactions has led to new concepts in self-assembly such as asymmetric dendrons 1 , 2 , Janus particles 3 , patchy colloids 4 , 5 , 6 and colloidal molecules 7 . Recent models that include attractive regions or ‘patches’ on the surface of the nanoparticles predict a wealth of intricate modes of assembly 8 , 9 , 10 , 11 , 12 . Interactions between such particles are also important in a range of phenomena including protein aggregation 13 , 14 and crystallization 15 , re-entrant phase transitions 16 , 17 , 18 , assembly of nanoemulsions 19 and the organization of nanoparticles into nanowires 20 . Here, we report the synthesis of 6-nm nanoparticles with dynamic hydrophobic patches and show that they can form reversible self-assembled structures in aqueous solution that become topologically more connected upon dilution. The organization is based on guest–host supramolecular chemistry with the nanoparticles composed of a hydrophobic dendrimer host molecule and water-soluble hydrophilic guest molecules. The work demonstrates that subtle changes in hierarchal composition and/or concentration can dramatically change mesoscopic ordering. Nanoparticles with dynamic patches can form reversible self-assembled structures in aqueous solution that become topologically more connected on dilution.