Bipyridine-centered poly(N-isopropylacrylamide) polymers with controlled molecular weight and low polydispersity were synthesized by RAFT polymerization using a novel bipyridine-functionalized dithioester as a RAFT agent, and were further complexed with ruthenium ion to produce ruthenium-centered thermosensitive polymers with well-defined structure. Results from UV-vis, fluorescence and DSC characterizations of the thermosensitive polymeric ruthenium complexes indicated that tris(2,2 -bipyridine)ruthenium(II) ion was successfully grafted onto the center of polymer chains. (c) 2005 Elsevier Ltd. All rights reserved.