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Star Gels. New Hybrid Network Materials from Polyfunctional Single Component Precursors

Published online by Cambridge University Press:  10 February 2011

Kenneth G. Sharp and
Michael J. Michalczyk
Kenneth G. Sharp
Affiliation:
Central Research, DuPont Co., Wilmington, DE, 19880-0323 U.S.A.
Michael J. Michalczyk
Affiliation:
Central Research, DuPont Co., Wilmington, DE, 19880-0323 U.S.A.
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Abstract

A new family of hybrid inorganic/organic network materials – the star gels – has been synthesized from single component molecular precursors. The starting materials comprise an organic core with multiple flexible arms which terminate in network-forming trialkoxysilane groups. The core can be a single silicon atom, linear disiloxane segment or ring system. With at least 12 alkoxysilane groups per molecule, gelation rates in aqueous or formic acid media can be extremely high, but can be attenuated several orders of magnitude by choice of solvent system. The degree of intramolecular condensation of these molecules has been assessed via mass spectrometric techniques. Transparent glasses which show brittle fracture but high levels of toughness have been generated from this family of precursors. The materials do not show plastic deformation even under compressive stress of 350 MPa. No evidence for open porosity in the glasses has been obtained. The organic content of the networks can be increased by lengthening the arms; the inorganic content can be increased via co-hydrolysis with simple tetraalkoxysilanes such as TEOS. Species with longer arms lead to glasses with higher coefficients of thermal expansion.

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Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 435: Symposium V – Better Ceramics Through Chemistry VII , 1996, 105
Copyright
Copyright © Materials Research Society 1996

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