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Interaction of Nanooxides with Poly(vinyl alcohol)

Gun'ko V., Zarko V., Andriyko L., Leboda R., Skubiszewska-Zięba J., Janusz W.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 3

411-424

EN

Interaction of silica, alumina/silica and titania/silica nanooxideswith poly(vinyl alcohol) was investigated in gaseous and aqueous media using infrared spectroscopy, adsorption, AFM and photon correlation spectroscopy methods. Formation of PVA monolayer on oxide nanoparticles leads to relatively small changes in morphological and textural characteristics of the materials. The characteristics of interfacial water/PVA layer, particle size distribution and Cd(II) adsorption depend on surface content of alumina or titania affecting amounts of Brönsted and Lewis acid sites. Arelativelyweak influence of various pretreatments on the structural characteristics of the materials depicts the stability of PVA/nanooxide composites as dry powders and aqueous dispersions.

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Nanosilica Partially Modifiedby Hexamethyldisilazane in Air

Gun'ko V., Voronina O., Voronin E., Zarko V., Pakhlov E., Leboda, Skubiszewska-Zięba J., Janusz W., Chibowski S.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 11

1787-1804

EN

Unmodified and modified nanosilicas containing different content of trimethylsilyl (TMS) groups grafted by interaction with various amounts of hexamethyldisilazane (HMDS) in a reactor contacting with air were studied using infrared spectroscopy, adsorption and potentiometric titration methods. Contribution of narrow gaps between spherical primary silica particles forming aggre gates decreases with in creasing TMS loading (tetaTMS), because of blocking of these gaps by grafted functionalities. Contribution of broader gaps corresponding to mesopores de ends slightly on tetaTMS, and changes in contribution of macropores are rather random. IR spectra of modified samples depict changes in bands of the O-H stretch ingvibrations at 3750 and 3300 cm-1 (reduced with qTMS) and 3680 and 3500 cm-1 (changed nonlinearly with qTMS), since HMDS can interact with silanols and ad sorbed water and af fect the ad sorbed amounts of water. Enhance ment of the hydrophobic properties of the surface reduces the amounts of adsorbed water, and the IR band in tensity at 3300 cm-1 di minishes. The adsorption of poly(vinyl pyrrolidone) on silicas decreases with tetaTMS in consequence of changes in the surface structure and the reduction of adsorption potential. The silylation diminishes the su face charge density and the electrostatic surface poten tial, and the point of zero charge shifts to ward larger pH values with in creasing tetaTMS value.

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Pathways for Decomposition of Phenylethanol Bound to Silica Surface

Gun'ko V., Leboda R., Pokrovsky V.

Polish Journal of Chemistry

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1999

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Vol. 73, nr 8

1345-1356

EN

Thermal desorption and decomposition of 2-phenylethanol bound to the silica gel surface were studied after its partial carbonization at 400 C and washing off pitch compounds not bound chemically to the surface. Various possible unimolecular and bimolecular reactions were discussed, based on investigations by temperature-programmed desorption (TPD) mass spectrometry and theoretical methods.