Self-assembly of thermo-sensitive poly (t-butyl acrylate)-b-poly(N-isopropylacrylamide) (PtBA-b-PNIPAM) micelles in aqueous medium and its applications in controlled release of hydrophobic drugs were described. PtBA-b-PNIPAM was synthesized by atom transfer radical polymerization and aggregated into thermo-sensitive core-shell micelles with regular spheres in water, which was confirmed by H-1-NMR, fluorescence spectroscopy, transmission electron microscopic (TEM), and UV-vis spectroscopic techniques. The critical micelle concentration of micelles decreased with the increase of the hydrophobic components. The anti-inflammation drug naproxen (NAP) was loaded as the model drug into polymeric micelles, which showed a dramatic thermo-sensitive fast/slow switching behavior around the lower critical solution temperature (LCST). When the temperature was enhanced above LCST, release of NAP from core-shell micelles was accelerated ascribed to the temperature-induced deformation of micelles. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 1364-1368, 2009