Tunable core–shell nanoparticles: macro-RAFT mediated one pot emulsion polymerization

Abstract

Simple and robust one-pot synthesis of polystyrene (PS) nanoparticles composed of a poly(hydroxyethyl methacrylate) (PHEMA) based macro-RAFT (reversible addition fragmentation chain transfer) agent has been developed. Initially generated hydrophilic PHEMA macro-RAFT agents were chain-extended in situ with a hydrophobic monomer (styrene) to form nanoparticles with core–shell morphology in which the PS core is covered with the PHEMA shell. Nanoparticle sizes and the dimensions (thickness) of core and shell were readily tuned by varying hydrophilic monomer (HEMA) concentration and polymerization time for the formation of a PHEMA based macro-RAFT agent. Field emission scanning electron microscopy showed the influence of molecular weight of the hydrophilic macro-RAFT agent on polymer particle size and self-assembly. The results suggested that unreacted HEMA during the nucleation process has a significant influence on the polymer morphology. In summary, we demonstrated that the current strategies can be effectively used to generate core–shell particles along with dimension tuning in a one-pot process.