Well-defined organic/inorganic hybrid fluorinated star polymers were synthesized via atom transfer radical polymerization (ATRP) of 2,2,3,4,4,4-hexafluorobutyl methacrylate (HFBMA) using octa(aminophenyl)silsesquioxane (OAPS) nano-cage as initiator. For this purpose, OAPS was transformed into ATRP initiator by reacting with 2-bromoisobutyrylbromide. ATR polymerization of HFBMA was carried out in trifluorotoluene at 75 degrees C using CuCl/2,2-bipyridine or N,N,N',N",N"-pentamethyldi-ethylenetriamine as catalyst system. GPC and H-1 NMR data confirmed the synthesis of OAPS/PHFBMA hybrid star polymer. Kinetics of the ATR polymerization of HFBMA using OAPS nano-cage initiator was also investigated. The OAPS/PHFBMA hybrid stars were found to be molecularly dispersed in solution (THF); however, TEM micrographs revealed the formation of spherical particles of similar to 120-180 nm by the OAPS/PHFBMA hybrid star polymer after solvent evaporation. Thermal characterization of the nanocomposites by differential scanning calorimetry (DSC) revealed a slightly higher glass transition temperature (T-g) (when compared with the linear PRFBMA) of higher molecular weight OAPS/PHFBMA hybrid star polymers. In contrast, lower T-g than the linear PHFBMA was observed for OAPS/PHFBMA of relatively lower molecular weight (but higher than the linear PHFBMA). Thermal gravimetric analysis (TGA) showed a significant retardation (by similar to 60 degrees C) in thermal decomposition of nanocomposites when compared with the linear PHFBMA. Additionally, surface properties were evaluated by measuring the contact angles of water on polymer surfaces. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym, Chem 46: 7287-7298, 2008