Novel organic-inorganic hybrid nanobuilding blocks of methacrylate- and acrylate-functionalized polyhedral oligomeric silsesquioxanes were easily prepared via nucleophilic substitution on octakis(3-chloropropyl)octasilsesquioxane, using sodium methacrylate and sodium acrylate, respectively. From a practical standpoint, these cage-rearranged silsesquioxanes (T-8, T-10, and T-12) could be readily isolated in their pure form with conventional silica gel column chromatography. Octakis(3-propyl methacrylate)octasilsesquioxane (T-8) is a colorless, crystalline solid with a melting point of 66.7-67.2 degrees C, while other cage products are colorless viscous liquids at room temperature. Moreover, we report that the chemical structure/physical property relationship of silsesquioxane cages not only is dependent on the symmetry of the inorganic silsesquioxane core at a given temperature but also is dictated by the organic substituent mobility. Structures of the products were confirmed by H-1, C-13, and Si-29 NMR spectroscopy and high resolution electrospray ionization mass spectrometry analysis.