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Origin of Porosity in Arylene-Bridged Polysilsesquioxanes

Published online by Cambridge University Press:  10 February 2011

Dale W. Schaefer ,
Greg B. Beaucage ,
Douglas A. Loy ,
Tamara A. Ulibarri ,
Eric Black ,
Kenneth J. Shea  and
Richard J. Buss
Dale W. Schaefer
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185–0340, dwschae@sandia.gov
Greg B. Beaucage
Affiliation:
Materials Science and Engineering, University of Cincinnati, Cincinnati, OH 45221–0012
Douglas A. Loy
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185–0340, dwschae@sandia.gov
Tamara A. Ulibarri
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185–0340, dwschae@sandia.gov
Eric Black
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185–0340, dwschae@sandia.gov
Kenneth J. Shea
Affiliation:
Department of Chemistry, University of California Irvine, Irvine, CA 92717
Richard J. Buss
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185–0340, dwschae@sandia.gov
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Abstract

We investigate the porosity of a series of xerogels prepared from arylene-bridged silsesquioxane xerogels as a function of organic bridging group, condensation catalyst and post-synthesis plasma treatment to remove the organic functionalities. We conclude that porosity is controlled by polymer-solvent phase separation in the solution with no evidence of organic-inorganic phase separation. As the polymer grows and crosslinks, it becomes increasingly incompatible with the solvent and eventually microphase separates. The domain structure is controlled by a balance of network elasticity and non-bonding polymer-solvent interactions. The bridging organic groups serve to ameliorate polymer-solvent incompatibility. As a result, when the polymer does eventually phase separate, the rather tightly crosslinked network limits domain size to tens of angstroms, substantially smaller than that observed in xerogels obtained from purely inorganic precursors where incompatibility drives phase separation earlier in the gelation sequence.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 435: Symposium V – Better Ceramics Through Chemistry VII , 1996 , 301
Copyright
Copyright © Materials Research Society 1996

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