The controlled synthesis and characterization of a range of stimuli responsive cationic terpolymers containing varying amounts of N-isopropylacrylamide (NIPAM), 3-(methylacryloylamino)propyl trimethylammonium chloride (MAPTAC), and poly(ethylene glycol)monomethyl methacrylate (PEGMA) is presented. The terpolymers were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. Compositions of the terpolymers determined using H-1 NMR were in close agreement to the theoretical values determined from the monomer feed ratios. GPC-MALLS was used to analyze the molecular weight characteristics of the polymers, which were found to have low polydispersities (M-w/M-n 1.1-1.4). The phase transitions were studied as a function of PEGMA and NIPAM content using temperature controlled 1H NMR and turbidity measurements (UV-Vis). The relationship between thermal stability and the comonomer ratio of the polymers was measured using thermogravimetric analysis (TGA). Protein interaction studies were performed to determine the suitability of the polymers for biological applications. (c) 2008 Wiley Periodicals, Inc.