Controlled magnetite nanoclustering in the presence of glycidyl-functionalized thermo-responsive poly(N-isopropylacrylamide)

Glycidyl-functionalized poly(N-isopropylacrylamide) (PNIPAAm), synthesized via a reversible addition-fragmentation transfer polymerization (RAFT), was used for controlling degree of nanoclustering of magnetite nanoparticle (MNP). The polymer was grafted onto MNP via the ring-opening reaction between glycidyl groups at the PNIPAAm chain terminal and amino groups on the MNP surface to obtain thermo-responsive MNP nanocluster. Hydrodynamic size (Dh) and colloidal stability of the nanocluster, corresponding to the degree of nanoclustering reaction, can be regulated either by adjusting the ratio of MNP to the polymer in the reaction or by introducing glycidyl groups to the polymers. The size of the nanocluster ranged between 20 and 150 nm in diameter with about 10-120 particles/cluster. Thermogravimetric analysis (TGA) and vibrating sample magnetometry (VSM) were used to confirm the presence of the polymer in the nanocluster. A study showing indomethacin controlled release of these MNP nanoclusters was also performed. This stable nanocluster with magnetically guidable properties might be potentially used for entrapment of other bio-entities or therapeutic drugs with temperature-responsive properties for controlled release applications. (C) 2016 Elsevier Ltd. All rights reserved.