We study how progressive changes in silane structure affect the synthesis and properties of organosilicas. Tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), methyltrimethoxysilane (MTMS), bis(trimethoxysilyl)ethane (BTMSE), bis(trimethoxysilyl)hexane (BTMSH), and bis(trimethoxysilylpropyl)amine (BTMSPA) are used as precursors in non-templated base and acid-catalyzed sol-gel processes, and in templated processes with cetyltrimethylammonium bromide (CTAB) and polyoxyethylene 10 lauryl ether (C12E10). The gel time of materials made without templates is mainly controlled by the structure of the silane rather than its reactivity. For instance, a dangling methyl group (MTMS) inhibits gelation, while a short bridging chain (BTMSE) promotes gelation. In basic conditions, mesoporous materials are obtained with TEOS and TMOS, while microporous materials are obtained with organically modified silanes without added amine. Dipropylamine, originally added as a catalyst, in fact templates mesopores in BTMSH-derived organosilica. In acidic conditions without pore templates, all products are microporous. In the presence of CTAB, mesopore templating occurs with TEOS, TMOS, BTMSE, and BTMSPA. With C12E10, mesopore templating occurs with TEOS, TMOS, and BTMSE. Surprisingly, the BTMSE-based material has the most uniform mesopores of all samples in the C12E10 series. Mesopore templating fails when a dangling organic limits the formation of stable pore walls (MTMS) or a large hydrophobic chain disrupts the formation surfactant micelles (BTMSH).
|Number of pages||10|
|Journal||Journal of Non-Crystalline Solids|
|State||Published - Dec 15 2006|
Bibliographical noteFunding Information:
This report is based on work partially supported by the National Science Foundation through CAREER grant number CTS-0348234. B.T. acknowledges partial support for this work through a Kentucky Research Challenge Trust Fund Fellowship.
- Organic-inorganic hybrids
- Sol-gels (xerogels)
- Solution chemistry
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry