Ultrafast Monomer Emulsified Aqueous Ring-Opening Metathesis Polymerization for the Synthesis of Water-Soluble Polynorbornenes with Precise Structure.

Abstract

Ring-opening metathesis polymerization (ROMP) in an aqueous medium provides an important environmentally friendly platform for the preparation of water-soluble polymeric materials. However, it is challenging to keep high synthetic efficacy and good control over molecular weight and distribution due to the inevitable catalyst decomposition in an aqueous medium. To meet this challenge, we propose a facile monomer emulsified aqueous ROMP (ME-ROMP) by injecting a tiny amount of a CH2Cl2 solution of the Grubbs' third-generation catalyst (G3) into the aqueous solution of norbornene (NB) monomers without deoxygenation. Driven by the minimization of interfacial tension, the water-soluble monomers could serve as surfactants with hydrophobic NB moieties inserted into the CH2Cl2 droplets of G3, leading to the significantly suppressed catalyst decomposition and accelerated polymerization. The ME-ROMP is confirmed to be living with an ultrafast polymerization rate, near quantitative initiation and monomer conversion, for the highly efficient and ultrafast synthesis of well-defined water-soluble polynorbornenes with various compositions and architectures.