The reversible addition–fragmentation
chain transfer (RAFT)
aqueous dispersion polymerization of 4-hydroxybutyl acrylate (HBA)
is conducted using a water-soluble RAFT agent bearing a carboxylic
acid group. This confers charge stabilization when such syntheses
are conducted at pH 8, which leads to the formation of polydisperse
anionic PHBA latex particles of approximately 200 nm diameter. The
weakly hydrophobic nature of the PHBA chains confers stimulus-responsive
behavior on such latexes, which are characterized by transmission
electron microscopy, dynamic light scattering, aqueous electrophoresis,
and1H NMR spectroscopy. Addition of a suitable water-miscible
hydrophilic monomer such as 2-(N-(acryloyloxy)ethyl
pyrrolidone) (NAEP) leads to in situ molecular dissolution of the
PHBA latex, with subsequent RAFT polymerization leading to the formation
of sterically stabilized PHBA–PNAEP diblock copolymer nanoparticles
of approximately 57 nm diameter. Such formulations constitute a new
approach to reverse sequence polymerization-induced self-assembly,
whereby the hydrophobic block is prepared first in aqueous media.