Scalable Preparation of Well-Defined Hierarchical Colloidal Materials by Heterogeneous Orthogonal RAFT Polymerization in Water

Hierarchical assembly of nanosized building blocks has emerged as an effective strategy for the bottom-up fabrication of functional materials with a wide range of potential applications, but large-scale production of well-defined hierarchical colloidal materials still remains challenging. In this study, cross-linked block copolymer micelles with reversible addition-fragmentation chain transfer (RAFT) groups at the interface were prepared by orthogonal RAFT-mediated polymerization-induced self-assembly (PISA) of hydroxypropyl methacrylate (HPMA) in water. These micelles were then used as building blocks for the polymerization-induced hierarchical self-assembly (PIHSA) of N-isopropylacrylamide (NIPAM) in water. We demonstrated that the presence of RAFT groups at the interface of micelles could promote the PIHSA process that enables the preparation of hierarchical colloidal materials with higher-order structures (e.g., vesicles). Careful monitoring the PIHSA process revealed some intermediate structures that provide mechanistic insights into the formation of hierarchical colloidal materials. This study provides a scalable and environmentally benign approach to prepare hierarchical colloidal materials with a diverse set of complex structures.