Theresa Eileen Gentle

Siloxane and hydrocarbon octopus molecules with silsesquioxane cores

Hydrogen silsesquioxane, (HSiO)8, T8, has been synthesized and isolated in synthetically useful quantities. The T8 cage-like structure allows eight pendant groups to be placed symmetrically about the surface of a sphere to form an ‘octopus’ molecule. Using T8 to hydrosilylate compounds with the formula CH2CH(X)nY, octopus molecules of the formula (SiO)8(CH2CH2(X)nY)8 have been synthesized, including octopus molecules with organic ‘arms’ as well as those with silicone ‘arms’ of various lengths. The regioselectivity of addition in the above two cases was found to differ. The synthesis of these novel octapus molecules and their characterisation by 29Si NMR, FTIR, and gel-permeation chromatography (GPC) is described.

Effect of catalyst on regioselectivity and vinyl/H exchange on silicon in the hydrosilylation of vinyl-siloxanes by T8 hydrogen silsesquioxane

We have recently reported the synthesis of octopus molecules of defined shape and size with molecular weights well into the thousands. These octopus molecules were made by placing eight pendant groups symmetrically about a central silsesquioxane core via the H2PtCl6 catalyzed hydrosilylation of 1-alkenes as well as vinyl- and allyl-siloxanes by T8 hydrogen silsesquioxane, (HSiO32)8. The chemistry of addition was studied and it was found that while the addition of the 1-alkenes to T8 was regioprecise with only α-addition being observed, both α- and β-addition occurred with vinyl-siloxane. In addition, H-vinyl exchange on silicon was observed to occur with addition of vinyl-siloxane to T8. In the current studies, the effect of the hydrosilylation catalyst. homogeneous and heterogeneous, on the regioselectivity of addition and on the extent of exchange on silicon was evaluated. It was found that the heterogeneous catalysts Pt−C, sulfided Pt−C, and Rh−C required higher temperature and longer times to get complete reaction than the homogeneous catalysts. H2PtCl6 and the tetramethyldivinyldisiloxane complex of Pt. Pd supported catalysts were not effective catalysts for this hydrosilylation. The extent of exchange on silicon and the degree of the second mode of addition occurring were higher with the heterogenous catalysts and may be a result of the higher reaction temperatures.

Oxidation of hydrogen silsesquioxane, (HSiO3/2)n9, by rapid thermal processing

ABSTRACT At Dow Corning Corporation, hydrogen silsesquioxane, (HSiO3/2)n, is beingcommercialized as a precursor to silica coatings for applications in the protection of electronic devices and as an interlayer dielectric layer in the fabrication of integrated circuits. Rapid Thermal Processing (RTP) has been used to convert hydrogen silsesquioxane to silica at temperatures as low as 400 °C with minimal to no adverse effects to temperature senSitive integrated circuits. The resulting silica films had lower mechanical stressand better chemical homogeneity than films processed in a conventionalfurnace using the same precursor and temperatures. Two different RTPunits, one employing an arc lamp and the other with tungsten-halogen lamps, gave comparable results. LINTRODUCTION Being developed at Dow Corning Corporation is a technology involving theapplication of thin (0. 1 to 0.3 .tm) inorganic coatings to integrated circuitsurfaces for environmental protection of electronic circuits1 (Figure 1).The first coating in direct contact with the circuit surface is a silica coatingthat is derived from the precursor, hydrogen silsesquioxane, (HSiO3/2)n,commonly called H-resin. The use of hydrogen silsesquioxane as aprecursor for thicker silica coatings (0.4 to 1 .0 rim) as an interlayer

Silica/Silicone Nanocomposite Films: A New Concept in Corrosion Protection

Thin films of silsesquioxane, (HSiO 3/2 ) n , were applied to aluminum panels and to CMOS microelectronic circuit surfaces by spin or dip coating organic solutions of the silsesquioxane. Nanoporous silica was obtained by oxidation of the silsesquioxane. These nanoporous silica films were then vacuum infiltrated with various viscosities of polydimethylsiloxanes (PDMS) to form hydrophobic nanocomposites. The nanocomposite films were shown to provide superior hermetic protection against salt fog exposure when compared to PDMS and silica films alone. The composite films were characterized by FTIR and optical microscopy. FTIR spectra showed that the silica served as a skeletal framework holding the hydrophobic PDMS in place and preventing loss of adhesion. This is in contrast to PDMS films alone in which blistering of the film from the substrate can occur, thus, allowing ions and moisture to reach the surface and corrosion to take place.