Monomer Emulsified Aqueous Ring-Opening Metathesis Polymerization (ME-ROMP) for the Synthesis of Water-Soluble Molecular Bottlebrushes with a Precise Structure

Water-soluble molecular bottlebrushes(MBBs) with various functionsand tunable morphologies have found promising application prospectsin the biorelevant field. However, the facile synthesis of water-solubleMBBs with well-defined architectures is challenging by different chemistry.Herein, we explore the versatility of monomer emulsified aqueous ring-openingmetathesis polymerization (ME-ROMP) for the facile synthesis of water-solubleMBBs via a grafting-through strategy. The grafting-through ME-ROMPwas carried out by injecting a tiny amount of Grubbs' third-generationcatalyst (G3) solution of CH2Cl2 into the aqueoussolution of norbornene macromonomers (NB MMs) without deoxygenation,forming NB MMs-stabilized CH2Cl2/H2O emulsions. In this ME-ROMP, the NB moieties and G3 are concentratedin CH2Cl2 droplets so that catalyst decompositioncould be significantly suppressed and the steric hindrance of MMsreduced, leading to an accelerated polymerization. The results demonstratethat the ME-ROMP of NB MMs is living with ultrafast polymerizationrates and near quantitative initiation and monomer conversion, producingwell-defined water-soluble MBBs with diverse compositions and tunablecontour lengths.