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Chemical Functionalization of Silica Aerogels

Published online by Cambridge University Press:  10 February 2011

Nicola Hüsing ,
Ulrich Schubert ,
Bernhard Riegel  and
Wolfgang Kiefer
Nicola Hüsing
Affiliation:
Institut für Anorganische Chemie der Technischen Universität Wien, Getreidemarkt 9, A-1060 Wien, Austria, [email protected]
Ulrich Schubert
Affiliation:
Institut für Anorganische Chemie der Technischen Universität Wien, Getreidemarkt 9, A-1060 Wien, Austria, [email protected]
Bernhard Riegel
Affiliation:
Institut für Physikalische Chemie der Universität Wtirzburg, Marcusstraße 9–11, D-97070 Wtirzburg, Germany
Wolfgang Kiefer
Affiliation:
Institut für Physikalische Chemie der Universität Wtirzburg, Marcusstraße 9–11, D-97070 Wtirzburg, Germany
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Abstract

Organofunctional silica aerogels were prepared by base catalyzed hydrolysis and condensation of Si(OR')4 / RSi(OMe)3 mixtures, followed by supercritical drying. In the trialkoxysilanes, R is of the type (CH2)nA, the group A being an organic function. Amino, ethylenediamino, mercapto, cyano, vinyl, and methacrylate groups were thus incorporated in the aerogels. The sol-gel reaction of a 4:1 mixture of Si(OMe)4 and (vinyl)Si(OMe)3 was exemplarily monitored by Raman spectroscopy. The Raman spectra show that under basic conditions hydrolysis and condensation of Si(OMe)4 is much faster than that of (vinyl)Si(OMe)3. For the other RSi(OMe)3 precursors the reaction rates strongly depend on the electronic properties and the polarity of the functional organic group. Addition of the aminopropyl and cyanoethyl substituted precursors to Si(OR)4 results in shorter gel times relative to pure Si(OR')4, while the mercaptopropyl, methacryloxypropyl and vinyl substituted precursors retard gelation. Depending on the ratio and the kind of the precursors, 70 - 100 % of the functional organic groups were incorporated into the aerogel network. The hydrophobicity of the aerogels depends on the kind and amount of RSiO1.5 units.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 435: Symposium V – Better Ceramics Through Chemistry VII , 1996 , 339
Copyright
Copyright © Materials Research Society 1996

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