The various monovinly-functional polyhedral oligomeric silsesquioxane (POSS) monomers had been copolymerized with ethylene (E) using rac-Et(Ind)(2) ZrCl2 and a modified methylaluminoxane (MMAO) cocatalyst. The unreacted POSS monomer could be removed completely by washing the copolymerization product with n-hexane. And the copolymers were characterized with H-1 NMR, TEM, DSC, TGA, and GPC to know the composition, thermal properties, molecular weight and its distribution, respectively. According to H-1 NMR data, the monomer reactivity ratios of various POSS monomers were calculated by the Fineman-Ross and Kelen-Tudos methods. Thermogravimetric analysis of E/POSS copolymers exhibited an improved thermal stability with a higher degradation temperature and char yields, demonstating that the inclusion of inorganic POSS nanoparticles made the organic polymer matrix more thermally robust. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 2697-2702, 2009