Cationic Polyelectrolyte-Stabilized Nanoparticles via RAFT Aqueous Dispersion Polymerization

Abstract

We report the synthesis of cationic sterically stabilized diblock copolymer nanoparticles via polymerization-induced self-assembly (PISA) using a RAFT aqueous dispersion polymerization formulation. The cationic steric stabilizer is a macromolecular chain-transfer agent (macro-CTA) based on quaternized poly(2-(dimethylamino)ethyl methacrylate) (PQDMA), and the hydrophobic core-forming block is based on poly(2-hydroxypropyl methacrylate) (PHPMA). The effect of varying synthesis parameters such as the salt concentration, solids content, relative block composition, and cationic charge density has been studied. In the absence of salt, self-assembly is problematic because of the strong repulsion between the highly cationic PQDMA stabilizer chains. However, in the presence of salt this problem can be overcome by reducing the charge density within the coronal stabilizer layer by either (i) statistically copolymerizing QDMA monomer with a nonionic comonomer (e.g., glycerol monomethacrylate, GMA) or (ii) using a binary mixture of a PQDMA macro-CTA and a poly(glycerol monomethacrylate) (PGMA) macro-CTA. These cationic diblock copolymer nanoparticles were analyzed by (1)H NMR spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), and aqueous electrophoresis. NMR studies suggest that the HPMA polymerization is complete within 2 h at 70 °C. Depending on the specific reaction conditions, either spherical, wormlike or vesicular nanoparticles can be prepared with tunable cationic surface charge.