Rapid and Efficient Synthesis of Star Polymers via Arm-First Monomer Emulsified Aqueous Ring-Opening Metathesis Polymerization (ME-ROMP)

The combination of ring-opening metathesis polymerization (ROMP) and the arm-first strategy is a widely employed "one-pot two-batch" approach for synthesizing star polymers. However, the intramolecular cross-linking during the core formation in a homogeneous system significantly restricts the production of high-molar-mass star polymers with complete conversion of arms. In this study, we present a successful synthesis of star polymers with diverse chemical compositions and high molar mass using a monomer emulsified ROMP (ME-ROMP) approach based on the arm-first strategy. The arm-first ME-ROMP method involves sequentially injecting CH2Cl2 solution containing a G3 catalyst and hydrophobic cross-linker into aqueous solution of norbornene monomers under stirring. Benefiting from the confinement effect provided by ME-ROMP, the intermolecular cross-linking during core formation was greatly enhanced, resulting in well-defined star polymers with varied chemical compositions and up to 95% conversion of arms within minutes. Furthermore, the star polymers containing cationic copolymer arms exhibited low toxicity and demonstrated potential applications in inflammation inhibition.