A facile one-pot strategy for preparation of small polymer nanoparticles by self-crosslinking of amphiphilic block copolymers containing acyl azide groups in aqueous media

In this paper, novel amphiphilic block copolymers, poly(N-isopropylacrylamide-co-4-(acyl azido) phenyl methacrylate)-block-poly(ethylene oxide), abbreviated as PEO-b-P(NIPAM-co-AAPMA), have been designed and synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization at room temperature. Then self-assembly of the block copolymers has been studied and small cross-linked polymer nanoparticles have been successfully prepared. The units of acyl azido methacrylate act as hydrophobic moieties and crosslinking sites, PEO chains act as stabilizers for the formed particles, and PNIPAM chains make the particles sensitive to temperature. It was found that the size of the polymer particles was related to the unit ratio of NIPAM and AAPAM and by tuning the unit ratio we could easily prepare small cross-linked polymer nanoparticles in aqueous media without using any additional crosslinking agents. The size of polymer nanoparticles was characterized to be about 17 nm by atomic force microscopy (AFM) and transmission electron microscopy (TEM). And the distribution of the particles is very narrow from the Laser light scattering (LLS) characterization.