Synthesis of High-Molecular-Weight Brush Polymers via RAFT Polymerization within the Micellar Nanoreactor of a PEG-Based Macromonomer

The RAFT polymerization of an amphipathic PEG-based macromonomer (mPEG-g-S) in water is performed. It is found that the polymerization proceeds via a micellar polymerization process. The polymerization kinetics, polymer chain extension, and polymer particle evolution of RAFT micellar polymerization are evaluated. It is demonstrated that the polymerization possesses a fast rate and high monomer conversion due to locally concentrating and orienting the hydrophobic polymerizing groups within the micellar nanoreactor. Moreover, the RAFT micellar polymerization is under good control since the polydispersity index (PDI) value of the synthesized brush copolymer is below 1.3 in most cases, even under polymerization conditions with the ratio of RAFT agent to macromonomer at 1:400. Polymerization leads to the formation of a completely grafted brush copolymer, and the as-synthesized brush copolymer will self-assemble into spherical particles during the polymerization process. This strategy is anticipated to be an efficient way for the controlled synthesis of completely grafted brush polymers with high molecular weights and their corresponding self-assembled particles.