pH-Responsive Nanogels Generated by Polymerization-Induced Self-Assembly of a Succinate-Functional Monomer

Colloidal nanogels formed from a pH-responsive poly(succinate)-functional core and a poly(sulfonate)-functional corona were prepared via a previously unreported reversible addition-fragmentation chain-transfer (RAFT)-mediated aqueous emulsion polymerization-induced self-assembly (PISA) route. Specifically, a poly(potassium 3-sulfopropyl methacrylate) (PKSPMA₅₀) macromolecular chain-transfer agent (macro-CTA) was synthesized via RAFT solution polymerization followed by chain-extension with a hydrophobic, carboxylic acid-functional, 2-(methacryloyloxy) ethyl succinate (MES) monomer at pH 2. Colloidal nanoparticles with tunable diameters between 66 to 150 nm, depending on the core composition, and narrow particle size distributions were obtained at 20% w/w solids. Well-defined pH-responsive nanogels that swell on increasing the pH could be prepared even without the addition of a cross-linking comonomer, and introducing an additional cross-linker to the core led to smaller nanogels with lower swelling ratios. These nanogels could reversibly change in size on cycling the pH between acidic and basic conditions and remain colloidally stable over a wide pH range and at 70 °C.