Abstract
A new and general route to synthesize shape-controlled bridged silsesquioxanes has been developed by the hydrolysis-condensation of molecularly designed precursors bearing urea groups. The auto-association of the bridging organic units, owing to the hydrogen bonds developing between the urea groups, has been exploited to create new multifunctional organo-bridged silicas with peculiar shapes from the nano- to the micro-scale. Helical fibers with controlled handedness, hollow tubes and spheres, and lamellar plates have been produced according to the main organic substructure and also depending on the reaction conditions (catalyst, solvent and temperature). Spectroscopic techniques (solid state 13C and 29Si NMR, FTIR and X-ray diffraction) and electronic microscopic measurements (SEM and TEM) allowed the characterisation of these hybrid materials.