271309 POSS-Templated Asymmetric Molecular Nanocages
Nanocages between 1-10 nm are interesting structures as their dimensions are similar to that of enzyme cavaties. The synthesis of the nanocage was accomplished using polyhedral oligomeric silsesquioxane (POSS) as templates. The template was constructed by derivatizing a commercially available POSS (octakis(dimethylsilyl)-POSS) to create an architecture dense in periphery functional vinyl groups. The forty eight periphery vinyl groups were linked to form a 3-D shell composed of carbosilane linkages. Dynamic light scattering measurements indicated that this shell cross linked structure had a diameter between 6.4 and 7.4 nm. NMR spectroscopy indicated that 86% of the vinyl groups were engaged in forming the shell and this number was consistent with the molecular weight measurements derived from GPC results. Since carbosilane linkages are stable in base we were able to preserve the integrity of the shell when we removed the template using tetraethyl ammonium hydroxide to generate a cavity containing 16 silanol groups. The walls of the nanocages obtained were asymmetric as the interior of the cages with the silanol functionalities were hydrophilic and the exterior surfaces with the carbosilane linkages were hydrophobic.