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Sol-Gel Chemistry by Ring-Opening Polymerization

  • Kamyar Rahimian (a1) and Douglas A. Loy (a1)

Abstract

Sol-gel processing of materials is plagued by shrinkage during polymerization of the alkoxide monomers and processing (aging and drying) of the resulting gels. We have developed a new class of hybrid organic-inorganic materials based on the solventless ring-opening polymerization (ROP) of monomers bearing the 2,2,5,5-tetramethyl-2,5-disilaoxacyclopentyl group, which permits us to drastically reduce shrinkage in sol-gel processed materials. Because the monomers are polymerized through a chain growth mechanism catalyzed by base rather than the step growth mechanism normally used in sol-gel systems, hydrolysis and condensation products are entirely eliminated. Furthermore, since water is not required for hydrolysis, an alcohol solvent is not necessary. Monomers with two disilaoxacyclopentyl groups, separated by a rigid phenylene group or a more flexible alkylene group, were prepared through disilylation of the corresponding diacetylenes, followed by ring closure and hydrogenation. Anionic polymerization of these materials, either neat or with 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane as a copolymer, affords thermally stable transparent gels with no visible shrinkage. These materials provide an easy route to the introduction of sol-gel type materials in encapsulation of microelectronics, which we have successfully demonstrated.

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[1] Brinker, C. J., Scherer, G. W., Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing, Academic Press, Inc.: San Diego, 1996.
[2] Loy, D. A., Shea, K. J., Chem. Rev. 1995, 95, 1431.10.1021/cr00037a013
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Sol-Gel Chemistry by Ring-Opening Polymerization

  • Kamyar Rahimian (a1) and Douglas A. Loy (a1)

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