A new terpyridine-functionalized dithioester was synthesized as a chain transfer agent in the reversible addition fragmentation chain transfer polymerization (RAFT) of N-isopropylacyamide (NIPAAm).The polymerization showed an first-order kinetics and the molecular weight increased linearly with conversion

indicating that the terpyridine-functionalized dithioester is an efficient chain transfer agent for the RAFT polymerization of NIPAAm.The terpyridine-functionalized poly(N-isopropylacyamide) (tpy-PNIPAAm) not only displays similar phase transition as PNIPAAm

but also have the coordination ability via terpyridine

which were further used to construct macromolecularmetal complex with ferrous ions as model metal ions.The appearance of a strong absorption at 555 nm in UV-Vis spectrum revealed the formation of macromolecular-metal complex

indicating the strong coordination ability of tpy-PNIPAAm to metal.Cloud point method and dynamic light scattering (DLS) were used to characterize the thermosensitivity of tpy-PNIPAAm and macromolecular-metal complex.The results showed that the macromolecularmetal complex could self-assemble into nanoparticles in aqueous solution due to the amphiphilic property The macromolecular-metal complex solution showed a similar phase transition as PNIPAAm.In addition

the nanoparticles of the macromolecular-metal complex in aqueous solution were stable even at temperature above the lower critical solution temperature(LCST) due to electrostatic repulsion.This work indicated the great potentials of tpyPNIPAAm as carriers for the delivery of therapeutic radioisotopes.