Publications

Disilaoxacyclopentanes have proven to be excellent precursors to sol-gel type materials. These materials have shown promise as precursors for encapsulation and microelectronics applications. The polymers are highly crosslinked and are structurally similar to traditional sol-gels, but unlike typical sol-gels they are prepared without the use of solvents and water, they have low VOC's and show little shrinkage during processing.

A novel alkylene-bridged disilaoxacyclopentanes were synthesized through the same methodology utilized in the synthesis of phenylene-bridged disilaoxacyclopentane. Disilaoxacyclopentanes were successfully polymerized using photo-acid generators. Furthermore, it was also been able to apply thin films of these materials to different substrates. Successful ring open polymerization (ROP) of these materials using photo-acid generators should allow to use these materials for applications such as conformal coatings and microlithography.

Oligomethylhydridosiloxane and tis copolymer with dimethylsiloxane undergo redistribution chemistry with catalytic tetrabutylammonium hydroxide (TBAH) to produce methylsilane and polymethylsilsesquioxanes. The rate and extent of redistribution reaction can be controlled by the amount of TBAH added, as well as use of solvent. The extent reaction can be followed by both infrared radiation (IR) and solid state NMR spectroscopy, following the disappearance of the SiH in the starting oligosiloxane.

Polysilsesquioxane foams and gels of the formula (RSiO1.5)n were produced via the catalytic an stoichiometric redistribution of organohydridosiloxanes. The extent of reaction was followed by both infrared (IR) and solid state NMR spectroscopy, following the disappearance of the SiH in the starting oligosiloxane.

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.