Shape-Controlled Bridged Silsesquioxanes: Hollow Tubes and Spheres

• Published in: Chemistry : a European journal Vol. 9; no. 7; pp. 1594 - 1599
• Main Authors: Moreau, Joël J. E., Vellutini, Luc, Wong Chi Man, Michel, Bied, Catherine
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 04.04.2003; WILEY‐VCH Verlag; Wiley; Wiley-VCH Verlag
• Subjects: bridged silsesquioxanes; Chemical Sciences; Chemistry; Chemistry, Multidisciplinary; hybrid silica; Material chemistry; nanostructures; Physical Sciences; Science & Technology; self-assembly; sol-gel; GELATORS; PERIODIC MESOPOROUS ORGANOSILICAS; ORGANIC GROUPS; bridged silsequioxanes; CRYSTAL; hybrid silica; NONLINEAR-OPTICAL MATERIALS; sol-gel; self-assembly; ORGANOGELS; nanstructures; HYBRID MATERIALS; HELICAL SILICA; CHANNEL WALLS; HANDED SILICA STRUCTURES; bridged silsesquioxanes • hybrid silica • nanostructures • self-assembly • sol-gel
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200390183

A new approach for the morphological control of bridged silsesquioxanes has been achieved by the hydrolysis of silylated organic molecules bearing urea groups. The urea groups are responsible for the auto‐association of the molecules through intermolecular hydrogen‐bonding interactions. The self‐assembly leads to supramolecular architectures that have the ability to direct the organization of hybrid silicas under controlled hydrolysis. The hydrolysis of the chiral diureido derivatives of trans‐(1,2)‐diaminocyclohexane 1 under basic conditions has been examined. The solid‐state NMR spectra (29Si and 13C) showed the hybrid nature of these materials with wholly preserved SiC covalent bonds throughout the silicate network. Hybrid silicas with hollow tubular morphologies were obtained by the hydrolysis of the enantiomerically pure compounds, (R,R)‐1 or (S,S)‐1, whereas the corresponding racemic mixture, rac‐1, led to a hybrid with ball‐like structures. The tubular shape is likely to result from a combination of two phenomena: the auto‐association abilities and a self‐templating structuration of the hybrid materials by the organic crystalline precursor. Electronic microscopy techniques (SEM and TEM) gave evidence for the self‐templating pathway. The formation of the ball‐like structures occurs through a usual nucleation growth phenomenon owing to a higher solubility of the corresponding crystals in the same medium. A new step has been overcome in the design of shape‐controlled nanostructured hybrid silicas. Tubular and spherical bridged silsesquioxanes were synthesized by the hydrolysis of silylated chiral diureido derivatives of trans‐(1,1)‐diaminocyclohexane. This result opens a novel approach to the development of new hybrid materials with tunable shapes and functionalities.