Polymerization-like Multilevel Hierarchical Self-Assembly of Polymer Vesicles into Macroscopic Superstructures with Controlled Complexity

We demonstrate a high-leveled hierarchical self-assembly process into fractal structures. Two hyperbranched multiarm copolymers are first coassembled into binary isotropic vesicles in the primary self-assembly. Then, these primary vesicles are in situ endowed with anisotropic hydrophobic “binding sites” through a pH-induced lateral microphase separation, undergoing an isotropic−anisotropic transition. Subsequently, the anisotropic vesicles further assemble together through the specific self-recognition between the binding sites into linear, branched, cyclization, and network-like vesicle chains. Furthermore, the obtained vesicle chains can transform into linear, branched, ring-like, and network tubes through successive vesicle fusion. Such a hierarchical process is pH-triggered and well-controlled by adjusting the vesicle compositions and is coined as “polymerization-like” self-assembly due to the striking analogy between the vesicle association model and polymerization process.