In Situ Synthesis of Branched Block Copolymer Assemblies via RAFT Dispersion Polymerization Using Branched Macro‐RAFT Agents†

Comprehensive Summary Here, we demonstrate the use of branched macromolecular reversible addition‐fragmentation chain transfer (macro‐RAFT) agents in RAFT dispersion polymerization, to access branched block copolymers as well as well‐defined branched block copolymer assemblies. Two types of branched macro‐RAFT agents were first synthesized by using either a monofunctional chain transfer monomer or a difunctional chain transfer monomer in RAFT polymerization, and subsequently utilized in RAFT dispersion polymerization. It was found that only branched macro‐RAFT agents synthesized from the difunctional chain transfer monomer could lead to colloidally stable assemblies with well‐defined morphologies. Reaction conditions including monomer concentration, degree of polymerization (DP) of the core‐forming block, and DP of the solvophilic segment on morphologies of branched block copolymer assemblies were investigated in detail. Size exclusion chromatography (SEC) analysis further confirmed the successful formation of branched block copolymers by using branched macro‐RAFT agents. This work on the synthesis of branched block copolymer assemblies by RAFT dispersion polymerization offers new opportunities for the rational design of polymer assemblies with well‐defined structures.