From a Water-Immiscible Monomer to Block Copolymer Nano-Objects via a One-Pot RAFT Aqueous Dispersion Polymerization Formulation

We describe the facile atom-efficient synthesis of diblock copolymer nano-objects via a one-pot RAFT aqueous dispersion polymerization protocol starting from a water-immiscible methacrylic monomer. More specifically, an aqueous emulsion of glycidyl methacrylate (GlyMA) is quantitatively converted into a 10% w/w aqueous solution of glycerol monomethacrylate (GMA) at 80 °C in air within 9 h in deionized water. 1 H NMR spectroscopy studies indicate no evidence for either methacrylic ester hydrolysis or polymerization during this ring-opening reaction. Kinetic analysis indicates that a significant rate acceleration occurs as the reaction mixture switches from a two-phase emulsion to a single aqueous phase. This observation is fully consistent with the GlyMA–GMA–water ternary phase diagram determined at 80 °C. The 10% w/w aqueous solution of GMA can be polymerized using RAFT chemistry to produce a near-monodisperse PGMA macromolecular chain-transfer agent (macro-CTA), which indicates that relatively little dimethacrylate impurity is produced during the conversion of GlyMA into GMA. This PGMA macro-CTA can be subsequently chain-extended using 2-hydroxypropyl methacrylate (HPMA) via a RAFT aqueous dispersion polymerization formulation. The resulting PGMA–PHPMA diblock copolymers can form well-defined spheres, worms, or vesicles depending on the relative block compositions, since this dictates the copolymer curvature and hence the self-assembly behavior. Bearing in mind that GMA is a relatively expensive specialty monomer and GlyMA is a commodity monomer, this appears to be a highly cost-effective, purely aqueous one-pot route to diblock copolymer nano-objects.