Water dispersible magnetite nanocluster coated with thermo‐responsive thiolactone‐containing copolymer

This work focused on surface modification of magnetite nanoparticle (MNP) with poly(poly(ethylene glycol) monomethyl ether methacylate)‐b‐(poly(N‐isopropylacrylamide)‐st‐poly(thiolactone acrylamide)), PPEGMA‐b‐(PNIPAAm‐st‐PTlaAm), diblock copolymer, synthesized via reversible addition‐fragmentation chain transfer (RAFT) polymerization to obtain the particles having good water dispersible PPEGMA brushes, thermo‐responsive PNIPAAm, and reactive thiolactone groups of PTlaAm. The thiolactone moiety in the copolymer can readily react with amino groups grafted on MNP surface and essentially induced the formation of MNP nanocluster. According to transmission electron microscopy (TEM), the size of the nanocluster ranged between 200 and 500 nm per cluster with 8 to 10 nm in diameter for each particle. Hydrodynamic diameter of the nanocluster significantly decreased as the dispersion temperature increased from 25°C to 45°C due to the shrinkage of thermo‐responsive PNIPAAm when crossing its lower critical solution temperature (LCST). This stable nanocluster might be potentially used as a magnetic carrier for control release of entrapped entities with a thermally triggering mechanism.