Directional Supracolloidal Self-Assembly Via Dynamic Covalent Bonds And Metal Coordination

Self-assembly of colloid particles into sophisticated directional nanostructures has attracted considerable attention over the last ten years. This can offer mechanical, electronic and magnetic properties that are essential in a range of important applications, e.g., energy storage, therapy and electronics. An emerging strategy towards the sophistication of supramolecular nanomaterials is the use of supracolloidal self-assembly, in which the micelles or colloids are used as building blocks. Binding directionality can produce nanostructures with attractive properties. Majority of the recent supracolloidal self-assembly that were exploited by Müller and other groups was achieved by virtue of the selective solvophobic interactions. Obviously, exploring of a strategy to high binding directionality is indispensable to achieve the sophistication in supracolloidal nanostructures.Herein, we report a general and versatile strategy toward a directional supracolloidal self-assembly via dynamic covalent bonds and coordination with abundant transition metal ions in water. To this end, poly(2-aminoethylmethacryl amide hydrochloride)-block-poly(2-hydroxypropylmethacrylamide)(PAEMA-b-PHPMA) was obtained via reversible addition-fragmentation chain transfer(RAFT) polymerisation under visible light irradiation at 25 oC. The hydrophobic terdendate ligand motifs can be achieved by the reaction of their NH2 groups with pyridine-2,6-dicarboxaldehyde(PDCA) via an imine conversion. These ligand motifs have high coordination constants with the abundant first-row transition metal ions, such as copper ions and zinc ions. Reversible reaction facilitates the permeation of metal ions into the core-shell interfaces. Conversely, metal-coordination promotes reaction over the interfaces. Cu(II)-coordination occurs overwhelmingly inside each isolated micelle. However, Zn(II)-coordination induced a directional self-assembly whose nanostructures evolve stepwise from nanorods, nanowires, necklaces, and finally to supracolloidal networks scaling-up to several tens of micrometres. Post reactions of simultaneous dynamic covalent bond conversion and Zn(II)-coordination over the core-shell interfaces endow these supracolloidal networks with huge specific surface area for hydrophobic dative metal centres accessible to substrates in water.What’s more, water-soluble shells play important roles in directional supracolloidal assembly and in the stabilization of nanostructures. Thus the directional self-assembly provides a versatile platform to produce metallo-hybridized nanomaterials for enzyme-inspired aqueous catalysts.