Chapter 71. Preparation of Highly Porous Silicates by Fast Gelation of H-Silsesquioxane

  1. Prof. Dr. Norbert Auner2 and
  2. Prof. Dr. Johann Weis3
  1. Duan Li Ou and
  2. Pierre M. Chevalier

Published Online: 5 MAY 2008

DOI: 10.1002/9783527619924.ch71

Organosilicon Chemistry V: From Molecules to Materials

Organosilicon Chemistry V: From Molecules to Materials

How to Cite

Ou, D. L. and Chevalier, P. M. (2003) Preparation of Highly Porous Silicates by Fast Gelation of H-Silsesquioxane, in Organosilicon Chemistry V: From Molecules to Materials (eds N. Auner and J. Weis), Wiley-VCH Verlag GmbH, Weinheim, Germany. doi: 10.1002/9783527619924.ch71

Editor Information

  1. 2

    Department of Inorganic Chemistry, University of Frankfurt, Marie-Curie-Straße 11, 60439 Frankfurt am Main, Germany

  2. 3

    Consortium of Electrochemical Industry GmbH, Zielstattstraße 20, 81379 Munich, Germany

Author Information

  1. New Venture R&D, Dow Corning Ltd., Barry CF63 2YL, UK Tel: +44 1446 723 504 — Fax: +44 1446 730 495

Publication History

  1. Published Online: 5 MAY 2008
  2. Published Print: 26 SEP 2003

ISBN Information

Print ISBN: 9783527306701

Online ISBN: 9783527619924

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Keywords:

  • fast gelation;
  • hydrogensilsesquioxanes;
  • aerogel;
  • ambient pressure drying;
  • highly porous hybrid

Summary

Aerogels exhibiting over 75% porosity have been prepared traditionally by supercritical drying of hydrolyzed alkoxysilanes. Recent work demonstrated the possibility of preparing, under ambient pressure, aerogel-type highly porous materials. However, a multiple-step process was required to reduce the capillary pressure (Pc), which caused shrinkage during the drying step and led to pore collapse. Surface modification of pore walls was also described, to increase the wetting angles between remaining solvent and the pore surface in order to reduce the capillary pressure. We report a fast, single-step route for the preparation of ultrahighly porous materials starting from hydrogensilsesquioxane and thus without any further surface modification. This novel approach relies on increasing the pore radius (rp) to reduce the capillary pressure upon drying. The increment of rp was achieved by the evolution of hydrogen gas during the gelation step, catalyzed by the use of activating agents. Variations of experimental conditions enable production, by a fast gelation process, of ultrahighly mesoporous monolithic materials (30 to 50 Å) with a very narrow pore size distribution.