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Controlling Porosity in Bridged Polysilsesquioxanes through Elimination Reactions

Published online by Cambridge University Press:  10 February 2011

Mark D. McClaint ,
Douglas A. Loy  and
Sheshasayana Prabakart
Mark D. McClaint
Affiliation:
Org. 1812, Sandia National Laboratories, Albuquerque, NM 87185-1407
Douglas A. Loy
Affiliation:
Org. 1812, Sandia National Laboratories, Albuquerque, NM 87185-1407
Sheshasayana Prabakart
Affiliation:
Advanced Materials Laboratory, University of New Mexico, Albuquerque, NM 87106
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Abstract

The retro Diels-Alder reaction was used to modify porosity in hydrocarbon-bridged polysilsesquioxane gels. Microporous polysilsesquioxanes incorporating a thermally labile Diels-Alder adduct as the hydrocarbon bridging group were prepared by sol-gel polymerization of trans-2, 3-bis(triethoxysilyl)norbornene. Upon heating the 2, 3-norbornenylene-bridged polymers at temperatures above 250°C, the norbornenylene-bridging group underwent a retro Diels-Alder reaction losing cyclopentadiene and leaving behind a ethenylene-bridged polysilsesquioxane. Less than theoretical quantities of cyclopentadiene were volatilized indicating that some of the diene was either reacting with the silanol and olefinic rich material or undergoing oligomerization. Both scanning electron microscopy and nitrogen sorption porosimetry revealed net coarsening of pores (and reduction of surface area) in the materials with thermolysis.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 435: Symposium V – Better Ceramics Through Chemistry VII , 1996 , 277
Copyright
Copyright © Materials Research Society 1996

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