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(4-6) 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(8-12). interactions between such particles are also important in a range of phenomena including protein aggregation(13,14) and crystallization(15), re-entrant phase transitions(16-18), 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.