Please use this identifier to cite or link to this item: doi:10.22028/D291-24588
Title: On the existence and hydrolytic stability of titanosiloxane bonds in the system : glycidoxypropyltrimethoxysilane-water-titaniumtetraethoxide
Author(s): Hoebbel, Dagobert
Nacken, Manfred
Schmidt, Helmut K.
Language: English
Year of Publication: 1998
OPUS Source: Journal of sol gel science and technology. - 13. 1998, S. 37-43
SWD key words: Hydrolyse
DDC notations: 620 Engineering and machine engineering
Publikation type: Journal Article
Abstract: Heterometal materials based on glycidoxypropyltrialkoxysilane and titaniumalkoxide are used for optical applications and require a high homogeneity on the molecular level. The presence of heterometal titanosiloxanes, their distribution and hydrolytic stability should influence the homogeneity of these materials. 29Si and 17O NMR spectroscopy has been used to investigate sols with molar ratios Si : Ti = 1 and H2O : OR (H) = 0.5-2.0 and their gels after heat treatment at 130°C. The presence of Si - O - Ti bonds in sols with a low water content (H < 0.2) and in the corresponding gels was identified by the high-field shift of the 29Si NMR signals of T1 and T2 units of up to 2-3 ppm compared to corresponding signals of homo-condensed Si - O - Si bonds. The existence of Si - O - Ti bonds in the sols is supported by 17O NMR spectra which show a characteristic signal around 340 ppm. A cleavage of the Si - O - Ti bonds occurs with increasing water/OR ratio in the sols. The cleavage of the heterometal bonds and the building up of homo-condensed species leads to a separation into areas with predominantly Ti - O - Ti and Si - O - Si bonds resulting in a decreased molecular homogeneity of the materials.
Link to this record: urn:nbn:de:bsz:291-scidok-28964
Date of registration: 18-Jun-2010
Faculty: SE - Sonstige Einrichtungen
Department: SE - INM Leibniz-Institut für Neue Materialien
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