29-O-02 Towards total hydrophobisation of MCM-41 type silica surface

Martin, Thierry; Galarneau, Anne; Brunel, Daniel; Izard, V.; Hulea, Vasile; Blanc, Alexandre; Abramson, Sébastien; Renzo, Francesco Di; Fajula, François

doi:10.1016/s0167-2991(01)81330-6

Cited by 45 publications

(55 citation statements)

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“…The three mesoporous silicas are silanized by grafting chlorodimethyloctylsilane as described in ref. 48. Before and after silanization, the MTS was characterized by nitrogen adsorption at 77 K (49).…”

Section: Methodsmentioning

confidence: 99%

Activated drying in hydrophobic nanopores and the line tension of water

Guillemot

Biben

Galarneau

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

125

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We study the slow dynamics of water evaporation out of hydrophobic cavities by using model porous silica materials grafted with octylsilanes. The cylindrical pores are monodisperse, with a radius in the range of 1-2 nm. Liquid water penetrates in the nanopores at high pressure and empties the pores when the pressure is lowered. The drying pressure exhibits a logarithmic growth as a function of the driving rate over more than three decades, showing the thermally activated nucleation of vapor bubbles. We find that the slow dynamics and the critical volume of the vapor nucleus are quantitatively described by the classical theory of capillarity without adjustable parameter. However, classical capillarity utterly overestimates the critical bubble energy. We discuss the possible influence of surface heterogeneities, long-range interactions, and high-curvature effects, and we show that a classical theory can describe vapor nucleation provided that a negative line tension is taken into account. The drying pressure then provides a determination of this line tension with much higher precision than currently available methods. We find consistent values of the order of −30 pN in a variety of hydrophobic materials. A remarkable property of water is its ability to form nanosize bubbles, or cavities, on hydrophobic bodies (1). Since their first direct observations through atomic force microscopy about a decade ago (2, 3), surface nanobubbles on hydrophobic surfaces have raised considerable interest, and they are believed to play a major role in surface-driven phenomena, such as boundary slippage of water flows, heat transfer at walls, vaporization and boiling, surface cleaning, etc. (4, 5). In a different context, the evaporation of water in the vicinity of hydrophobic bodies has been studied as a core mechanism for the hydrophobic interaction mediated by water (6-8), which plays a central role in biological matter. The formation of cavities able to bridge hydrophobic units provides a driving force for protein folding and supermolecular aggregation (9). Simulation examples of such drying-induced phenomena include the collapse of a polymer chain, multidomain proteins, and hydrophobic particles (9-13).Despite their direct observation, the easy formation and the high stability of nanobubbles on hydrophobic bodies still raise fundamental questions (5,14,15). Because of significant theoretical work, it is now established that, at the scale of the nanometer, macroscopic concepts apply: hydrophobicity is described by interfacial energies, and the drying transition in hydrophobic confinement is a first-order transition triggered by the nucleation of a critical vapor bubble (1). The energy barrier limiting the kinetics of this transition is a strong signature of nanobubbles properties. Evaporation kinetics has also been pointed out as the most direct measure of the importance of hydrophobic collapse in protein folding (9). However, rate effects in the drying transition have not received much attention. A few numerical studies have addr...

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Section: Methodsmentioning

confidence: 99%

Activated drying in hydrophobic nanopores and the line tension of water

Guillemot

Biben

Galarneau

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

125

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“…C BET is characteristic of adsorbate/material interactions and increases when interactions strength increases. For instance, nitrogen molecules interact strongly with hydrophilic surfaces corresponding to C BET~1 00, whereas for hydrophobic surfaces (as octyl-grafted silicas) [25,26] the interactions are weaker (C BET~2 0) and the projection of the surface area of a nitrogen molecule change from 0.135 to 0.162 nm 2 , respectively. For 20-30 < C BET < 90-100, corresponding to hydrophobic-hydrophilic surfaces, the surface of a nitrogen molecules will be 0.135 < σ N 2 < 0.162 nm 2 .…”

Section: Characterization Of the Mesoporosity In Hierarchical Silicamentioning

confidence: 99%

Synthesis and Textural Characterization of Mesoporous and Meso-/Macroporous Silica Monoliths Obtained by Spinodal Decomposition

et al. 2016

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Silica monoliths featuring either mesopores or flow-through macropores and mesopores in their skeleton are prepared by combining spinodal phase separation and sol-gel condensation. The macroporous network is first generated by phase separation in acidic medium in the presence of polyethyleneoxides while mesoporosity is engineered in a second step in alkaline medium, possibly in the presence of alkylammonium cations as surfactants. The mesoporous monoliths, also referred as aerogels, are obtained in the presence of alkylpolyethylene oxides in acidic medium without the use of supercritical drying. The impact of the experimental conditions on pore architecture of the monoliths regarding the shape, the ordering, the size and the connectivity of the mesopores is comprehensively discussed based on a critical appraisal of the different models used for textural analysis.

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“…The resulting material was simply denominated SBA-15. The aminopropyl grafting of SBA-15 was implemented by applying APTES as the silylation reagent [21]. 1.0 g of SBA-15 powder was mixed with 1 mL of APTES in dry toluene solution and then the mixed solution was kept with reflux for 12 h under Ar atmosphere.…”

Section: Synthesis Of Functionalized Mesoporous Silicamentioning

confidence: 99%