Hollow Nanoparticles Prepared From pH-Responsive Template Polymer Micelles

Water-soluble crosslinked hollow nanoparticles were prepared using pH-responsive anionic polymer micelles as templates. The template micelles were formed from pH-responsive diblock copolymers (PAMPS-PAaH) composed of the poly(sodium 2-(acrylamido)-2-methylpropanesulfonate) and poly(6-(acrylamido)hexanoic acid) blocks in an aqueous acidic solution. The PAMPS and PAaH blocks form a hydrophilic anionic shell and hydrophobic core of the core-shell polymer micelle, respectively. A cationic diblock copolymer (PEG-P(APTAC/CEA)) with the poly(ethylene glycol) block and random copolymer block composed of poly((3-acrylamidopropyl)trimethylammonium chloride) containing a small amount of the 2-(cinnamoyl)ethylacrylate photo-crosslinkable unit can be adsorbed to the anionic shell of the template micelle due to electrostatic interaction, which form a core-shell-corona three-layered micelle. The shell of the core-shell-corona micelle is formed from a polyion complex with anionic PAMPS and cationic P(APTAC/CEA) chains. The P(APTAC/CEA) chains in the shell of the core-shell-corona micelle can be photo-crosslinked with UV irradiation. The template micelle can be dissociated using NaOH, because the PAaH blocks are ionized. Furthermore, electrostatic interactions between PAMPS and PAPTAC in the shell are screened by adding excess NaCl in water. The template micelles can be completely removed by dialysis against water containing NaOH and NaCl to prepare the crosslinked hollow nanoparticles. Transmission electron microscopy observations confirmed the hollow structure. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 2596-2603, 2012