Mechanism and Kinetics of Hexamethyldisilazane Reaction with a Fumed Silica Surface

Gun'ko, V.М.; Vedamuthu, M.S.; Henderson, Giles; Blitz, Jonathan P.

doi:10.1006/jcis.2000.6934

Cited by 84 publications

(62 citation statements)

References 36 publications

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“…The preparation of modified silicas and their structural and adsorptive properties were described in details elsewhere [35][36][37][38][39]. Choice of modified fumed silica is caused by a weaker effect of confined space between primary particles in their aggregates and between these aggregates in agglomerates in comparison with porous adsorbents [30,31,[35][36][37][38][39].…”

Section: Methodsmentioning

confidence: 99%

Structured water in partially dehydrated yeast cells and at partially hydrophobized fumed silica surface

Туров

Gun'ko

Богатырев

et al. 2005

Journal of Colloid and Interface Science

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Section: Methodsmentioning

confidence: 99%

Structured water in partially dehydrated yeast cells and at partially hydrophobized fumed silica surface

Туров

Gun'ko

Богатырев

et al. 2005

Journal of Colloid and Interface Science

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“…Kinetic studies and quantum chemical calculations have revealed the electrophilic substitution mechanism and second-order reaction kinetics for the reaction of HMDS with surface hydroxyl groups [17,18]. Consequently, in a highly reproducible process, HMDS transforms the hydrophilic substrate surface into a hydrophobic one by removing adhered water and reacting with surface bound hydroxyl groups which affect the photoresist adhesion [19].…”

Section: Introductionmentioning

confidence: 99%

Correlation of surface roughness and surface energy of silicon-based materials with their priming reactivity

et al. 2012

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In this work, the effect of surface roughness and cleaning procedures on reactivity during priming with hexamethyldisilazane is described for four silicon substrates frequently used in semiconductor technology, namely thermally grown SiO 2 , argon implanted tetraorthosilicate SiO 2 , polysilicon, and amorphous silicon. Surface energy and roughness were determined by static contact angle measurements and atomic force microscopy. The surface roughness of the silicon substrates increased in the order: thermally grown SiO 2 , argon implanted tetraorthosilicate SiO 2 , polysilicon, and amorphous silicon. It was found not to be substantially affected by standard cleaning procedures. The surface energy of all silicon samples decreased with increasing hexamethyldisilazane vapor exposure at 90°C, and the extent of the decrease corresponded to the surface roughness. Furthermore, a promoting effect on the silylation reaction by an argon implantation process was determined. A correlation between the surface morphology of different silicon materials and reactivity in the silylation reaction with hexamethyldisilazane could be established.

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“…Such a shift seems rather important to us, since it leads to a decrease in the hydrogen bond energy by 5 kJ according to the E. D. Sokolov formula [11] Dn/n 0 = E·1.6·10 -2 (kcal), where n 0 = 3600 cm -1 , E is the energy. On the sample additionally modified by HMDS, the concentration of the most active adsorption sites decreases by a factor of 4 relative to the sample Silokhrom-80 + PEHS (4.8·10 -2 and 1.1·10 -2 OH/nm 2 respectively), which is connected with their blocking by -Si(CH 3 ) 3 radicals and partially by NH 3 molecules formed when the HMDS molecules decompose [12,13].…”

Section: Resultsmentioning

confidence: 96%

Two-step modification of silica to obtain energetically homogeneous chromatographic sorbents

2006

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We have carried out a two-step liquid-phase modification of amorphous silica Silokhrom-80 with polyethyl hydride siloxane and hexamethyldisilazane. Using the parameters of the Langmuir equation, we have determined the concentration of residual hydrophilic sites on the surface of the modified silica, and we have identified them. We have shown that two-step modification of silica by selected reagents makes it possible to completely deactivate the most active vicinal hydroxyl groups on the sorbent surface, and to deactivate its isolated hydroxyl groups to a significant extent.It is known [1] that despite the diversity of existing methods for chemical modification of the surface of silicas by different classes of organic compounds, in practice complete blocking of the surface hydroxyl groups has not been able to be achieved. With the goal of deactivating the residual silanol groups on the silica surface, two-step modification is practiced: in the second step, small organic molecules are used that react with the residual hydrophilic sites on the surface.The completeness of modification of silicas can be assessed by physicochemical methods, in particular from heats of adsorption of polar sorbates obtained by gas chromatography. This method, due to the specific experimental conditions (exceptionally low coverage of the surface and high temperatures) is more sensitive than wetting methods and structural sorption methods carried out at room temperature [2].In this work, we have carried out two-step modification of the disperse amorphous silica (aerosil gel) Silokhrom-80 by polyethyl hydride siloxane (PEHS) according to the procedure in [3] and by hexamethyldisilazane (HMDS). We used the oligomer PEHS because, in contrast to organic compounds reacting with surface OH groups according to a localized mechanism, along with chemical shielding it also provides physical shielding of the active surface sites [4]. However, the hydrophobic film formed on the silica surface has defects: breaks in continuity. So the second step of modification of the silica using HMDS is carried out to shield the active sites at such defects.Additional modification was carried out by treatment of the PEHS-modified silica with a 0.6% toluene solution of HMDS with solid : liquid ratio 1 : 3.5, heating the suspension obtained for 2 h at 110°C in a sand bath until the excess solvent was evaporated. The air-dried samples of Silokhrom-80 + PEHS and Silokhrom-80 + PEHS + HMDS were used for further studies.The specific surface areas of the considered samples were determined on an ASAP 2000M (Micromeritics, USA) from adsorption of nitrogen, and were calculated by the BET method [5]. For the original silica Silokhrom-80, S = 86 m 2 /g, while for the modified samples the specific surface area decreases down to 50-55 m 2 /g.

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Mechanism and Kinetics of Hexamethyldisilazane Reaction with a Fumed Silica Surface

Cited by 84 publications

References 36 publications

Structured water in partially dehydrated yeast cells and at partially hydrophobized fumed silica surface

Structured water in partially dehydrated yeast cells and at partially hydrophobized fumed silica surface

Correlation of surface roughness and surface energy of silicon-based materials with their priming reactivity

Two-step modification of silica to obtain energetically homogeneous chromatographic sorbents

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