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Titel: On the existence and hydrolytic stability of titanosiloxane bonds in the system : glycidoxypropyltrimethoxysilane-water-titaniumtetraethoxide
Verfasser: Hoebbel, Dagobert
Nacken, Manfred
Schmidt, Helmut K.
Sprache: Englisch
Erscheinungsjahr: 1998
Quelle: Journal of sol gel science and technology. - 13. 1998, S. 37-43
SWD-Schlagwörter: Hydrolyse
Kondensation
Siloxane
DDC-Sachgruppe: 620 Ingenieurwissenschaften und Maschinenbau
Dokumentart : Journalartikel
Kurzfassung: 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 zu diesem Datensatz: urn:nbn:de:bsz:291-scidok-28964
hdl:20.500.11880/24644
http://dx.doi.org/10.22028/D291-24588
SciDok-Publikation: 18-Jun-2010
Fakultät: Sonstige Einrichtungen
Fachrichtung: SE - INM Leibniz-Institut für Neue Materialien
Fakultät / Institution:INM
SE - Sonstige Einrichtungen

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