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Evolution of Porosity and Morphology in Alkylene-Bridged Polysilsesquioxane Xerogels as a Function of Gel Aging Time

Published online by Cambridge University Press:  01 February 2011

Douglas A. Loy ,
James H. Small ,
Kimberly A. DeFriend ,
Kennard V. Wilson Jr ,
McKenzie Minke ,
Brigitta M. Baugher ,
Colleen R. Baugher ,
Duane A. Schneider  and
Kenneth J. Shea
Douglas A. Loy
Affiliation:
Polymers and Coatings Department, Los Alamos National Laboratories, PO Box 1662, MS E549, Los Alamos, NM 87545, U.S.A.
James H. Small
Affiliation:
Polymers and Coatings Department, Los Alamos National Laboratories, PO Box 1662, MS E549, Los Alamos, NM 87545, U.S.A.
Kimberly A. DeFriend
Affiliation:
Polymers and Coatings Department, Los Alamos National Laboratories, PO Box 1662, MS E549, Los Alamos, NM 87545, U.S.A.
Kennard V. Wilson Jr
Affiliation:
Polymers and Coatings Department, Los Alamos National Laboratories, PO Box 1662, MS E549, Los Alamos, NM 87545, U.S.A.
McKenzie Minke
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185, U.S.A.
Brigitta M. Baugher
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185, U.S.A.
Colleen R. Baugher
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185, U.S.A.
Duane A. Schneider
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185, U.S.A.
Kenneth J. Shea
Affiliation:
Department of Chemistry, University of California Irvine, U.S.A.
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Abstract

Aging of silica gels before drying is known to result in significant changes in xerogel morphology, porosity and properties. In this study, the influence of aging gels on the porosity and morphology of alkylene-bridged polysilsesquioxane xerogels was examined. Gels of hexylene-, heptylene, octylene, nonylene, and decylene-bridged polysilsesquioxanes were prepared by the sol-gel polymerization of the respective bis(trimethoxysilyl)alkane monomers under acidic or basic conditions in methanol and in tetrahydrofuran. The gels were aged 3, 7, 14, 28, 35, 42, 49, and 56 days before drying to afford xerogels. The xerogels were characterized by nitrogen sorption porosimetry. Xerogels prepared in THF were non-porous. Those prepared and aged under basic conditions in methanol or tetrahydrofuran exhibited coarsening of porosity with aging time. With the exception of the hexylene-bridged gels, those prepared and aged in acidic methanol showed little change with aging. The surface area of the hexylene-bridged xerogels nearly tripled with aging times of up to several weeks, then decreased, for the gels aged for more than two weeks, to around 100 meters squared per gram.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 847: Symposium EE – Organic/Inorganic Hybrid Materials , 2004 , EE10.3
Copyright
Copyright © Materials Research Society 2005

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References

REFERENCES

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