Efficient Preparation of Monodisperse Block Copolymer Microspheres via One-Pot RAFT Dispersion Polymerization

Monodisperse polymeric microspheres are a versatile class of materials due to their unique characteristics and have been extensively applied in a diverse set of scientific and industrial areas such as biomedical analysis, calibration standards, electronics, and separation. In principle, polymeric microspheres are unique aggregates of polymer chains with micrometer-scale dimensions. However, synthetic methods that can simultaneously control the structure of polymers and achieve high size uniformity of polymeric microspheres remain experimentally unattainable. Here, we report an efficient, one-pot, and controlled synthesis of monodisperse polymeric microspheres at the molecular level via a dispersion polymerization approach in which a macromolecular reversible addition–fragmentation chain transfer (macro-RAFT) agent is used as a stabilizer and a small-molecule RAFT agent is used to control the polymerization inside polymeric microspheres. Key to our approach is the structural balance between the macro-RAFT agent and the RAFT agent, which enables the synthesis of monodisperse polymeric microspheres within well-defined polymers. We also showcase the capability of our approach by synthesizing well-defined homopolymers with different molecular weights and highly ordered multiblock copolymers, while the high size uniformity of polymeric microspheres is maintained. We further demonstrate the potential of our approach through the synthesis of diblock, triblock, and tetrablock copolymers containing incompatible blocks, which yield monodisperse nanostructured polymeric microspheres with well-defined internal morphologies.