(590b) 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.