Silsesquioxanes: POSS® Nanohybrids

Hybrid inorganic–organic composites are an emerging class of new materials that hold significant promise.1 Materials are being designed with the good physical properties of ceramics and the excellent choice of functional group chemical reactivity associated with organic chemistry. New silicon-containing organic polymers, in general, and polysilsesquioxanes, in particular, have generated a great deal of interest because of their potential replacement for, and compatibility with silicon-based inorganics in the electronics, photonics, and other materials technologies.2-4

Hydrolytic condensation of trifunctional silanes yields network polymers or polyhedral clusters having the generic formula (RSiO1.5)n.5,6 Hence, they are known by the "not quite on the tip of the tongue" name silsesquioxanes. Each silicon atom is bound to an average of one and a half (sesqui) oxygen atoms and to one hydrocarbon group (ane). Typical functional groups that may be hydrolyzed/condensed include alkoxy- or chlorosilanes, silanols, and silanolates.7

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(1) Hybrid Organic/Inorganic Materials, Proceedings of the Materials Research Society Spring 2000 Meeting; Laine, R. M., Sanchez, C., Giannelis, E., Brinker, C. J., Eds.; Vol. 628.
(2) Hybrid Inorganic-Organic Polymers. In Polymer Preprints; Stoney, R. F., Ed.; American Chemical Society: Washington D.C., 2000; Vol. 41, pp 502–625.
(3) Symposium on "3-D Silicon-Oxygen Cages: Materials for the 21st Century", American Chemical Society, 222nd National Meeting, Aug. 26-30, 2001; Primary sponsor: Materials Chemistry Secretariat.
(4) Provatas, A. et al. J. Organomet. Chem. 1998, 565, 159.
(5) Baney, R. H. et al. Chem. Rev. 1995, 95, 1409.
(6) Lichtenhan, J. D. Silsesquioxane-Based Polymers, The Polymeric Materials Encyclopedia: Synthesis, Properties and Applications; Salamone, J. C., Ed.; CRC Press: Boca Raton, Florida, 1996; p 7768.
(7) Brook, M.A .; Silicon in Organic, Organometallic, and Polymer Chemistry; Wiley: New York, 2000.