| Abstract
| - Fumed silicas unmodified (SBET = 378 m2/g) and modified (379−285 m2/g) by hexamethyldisilazanereacting with silanols (concentration of grafted trimethylsilyl groups CTMS = 0.09−0.79 mmol/g) werestudied by means of the NMR, IR, differential thermogravimetry, atomic force microscopy, microcalorimetry,adsorption, and theoretical methods. Variation in the surface composition and changes in the structuralcharacteristics of primary and secondary particles lead to the nonlinear dependence of the Gibbs freeenergy of interfacial water, the heat of immersion of silicas in water, and the chemical shift δH(T) of wateradsorbed from air on CTMS, despite a nearly linear decrease in water adsorption (at p/p0 ≈ 0.8 for 24−72h) with CTMS. An increase in CTMS causes alterations in the structure of the hydrogen bond network in theinterfacial water and other properties of water strongly (700−300 mg/g silica) and weakly (1400−500 mg/g)bound to the silica surfaces.
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