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Title: UV-Raman and Si-29 NMR Spectroscopy Investigation of the Nature of Silicate Oligomers Formed by Acid Catalyzed Hydrolysis and Polycondensation of Tetramethylorthosilicate
Authors: Depla, Anouschka ×
Verheyen, Elke
Veyfeyken, An
Van Houteghem, Marc
Houthoofd, Kristof
Van Speybroeck, Veronique
Waroquier, Michel
Kirschhock, Christine
Martens, Johan #
Issue Date: Jun-2011
Publisher: American Chemical Society
Series Title: Journal of Physical Chemistry C vol:115 issue:22 pages:11077-11088
Abstract: Tetramethylorthosilicate (TMOS) was hydrolyzed and polymerized under strongly acidic conditions in the presence of substoichiometric quantities of water. The polymerization reaction was monitored during 64 h using Si-29 NMR and UV-Raman spectroscopy. The nature of the oligomers and the condensation reaction pathways were unraveled using this combination of experimental techniques together with molecular modeling. Si-29 NMR and UV-Raman signals which previously were not documented in literature could be assigned. TMOS rapidly was converted into short straight methoxylated silicate chains. Subsequently the growth of oligomers proceeded by condensations between a hydrolyzed middle group of a chain with an end-group of another chain. Larger oligomers were attached to each other via condensations between middle groups generating multiply branched structures. Rings were formed late in the reaction scheme through internal condensations of sizable silicate molecules. Oligomers that were characteristic of the different stages of the polymerization process were proposed. Oligomerization pathways starting from tetramethylorthosilicate and tetraethylorthosilicate (TEOS) are significantly different. While with TMOS rings are formed only late in the oligomerization scheme, with TEOS rings are formed at early stages through cyclo-dimerization. This insight into the different nature of the oligomers obtained from TMOS and TEOS will assist the design of new silica sol gel materials.
ISSN: 1932-7447
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Centre for Surface Chemistry and Catalysis
× corresponding author
# (joint) last author

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