Staged Surface Patterning and Self-Assembly of Nanoparticles Functionalized with End-Grafted Block Copolymer Ligands.

Using two orthogonal external stimuli, programmable staged surface patterning and self-assembly of inorganic nanoparticles (NPs) was achieved. For gold NPs capped with end-grafted poly(styrene-block-(4-vinylbenzoic acid)), P(St-block-4VBA), block copolymer ligands, surface-pinned micelles (patches) formed from NP-adjacent PSt blocks under reduced solvency conditions (Stimulus 1); solvated NP-remote P(4VBA) blocks stabilized the NPs against aggregation. Subsequent self-assembly of patchy NPs was triggered by crosslinking the P(4VBA) blocks with copper(II) ions (Stimulus 2). Block copolymer ligand design has a strong effect on NP self-assembly. Small, well-defined clusters assembled from NPs functionalized with ligands with a short P(4VBA) block, while NPs tethered with ligands with a long P(4VBA) block formed large irregularly shaped assemblies. This approach is promising for high-yield fabrication of colloidal molecules and their assemblies with structural and functional complexity.