Effect Of Water And Ethanol On Interaction Of High Disperse Silica With Polyvinylpyrrolidone
effect of water and ethanol on interaction of high disperse silica with polyvinylpyrrolidone
N.V. Guzenko, E.F. Voronin, E.M. Pakhlov, A.A. Chuiko
Institute of Surface Chemistry, Ukrainian National Academy of Sciences,
General Naumov st. 17, 03164 Kiev, Ukraine,
e-mail: borysenko@naverex.kiev.ua
Adsorption of polymers on a surface of solid bodies as a rule is carried out from solutions, and the dried up samples are usually used for IR-spectral investigations. Therefore always a question arises about identity of adsorbed polymer layer in presence and in absence of a solvent [1]. Generally solvent can promote adsorption or interfere to it. The inhibition of adsorption of polymers from solutions frequently arises as a result of interaction of surface active centres preferably with molecules of a solvent [1-3].
Influence of solvents (water and ethanol) on interaction of water-soluble polymeric compounds with the surface of high disperse silica and on structure of the absorbed polymer layer was investigated by the IR spectroscopy method for the system polyvinylpyrrolidone (PVP, М=12000) – aerosil A-300 (SBET = 287 m2/g). For this purpose dry PVP and aerosil were mixed during 10 min with use of the vibrator "n.M.v. Ardenne" (GDR). PVP is adsorbed on the surface of silica from water solution due to formation of hydrogen bonds with free silanol groups, which are displayed in the IR-spectrum as absorption band at 3750 cm-1 [3, 4]. In case of mixing with dry PVP and further warming up this absorption band in the IR-spectrum of aerosil was unchanged. This testifies to absence of interaction between polymer and silica surface. After placing of this sample in saturated vapours of water, ethanol or water-ethanol mixture (1:1) at room temperature during 3-4 hours the band at 3750 cm-1 sharply decreases for the PVP contents 150 mg/g or completely disappears for CPVP =200mg/g. The content of 200 mg/g corresponds to formation of PVP monolayer on the surface of aerosil A-300. The solvent adsorption was from 25(water) to 30 %wt. (ethanol) that formally corresponds to formation of 10–15 layers. While this aerosil was dry and retained friability. Water and
ethanol on air at room temperature are completely evaporated from the sample during 1-2 hours, and at warming up to 60° C for 10-15 min., therefore they do not make any influence on IR-spectra.
It is important to note that the processes investigated proceed equally both for the sample previously pressed to a plate as well as for the not pressed powdery silica sample.
Thus, the received results prove that water or ethanol do not prevent the PVP adsorption on a surface of high disperse silica from solutions, and constitution of the adsorbed polymer layer is identical both in medium of a solvent, and in its absence.
References
1. Adsorption from Solution at the Solid/Liquid Interface /Ed. G.D.Parfit, C.H.Rochester - Academic Press London New York Paris, 1983.
2. Yu.S.Lipatov, L.M.Sergeeva. Adsorption of Polymers. – Naukova dumka, Kiev, 1972.
3. The Chemistry of Silica: / Ralph K. Iler. A Wiley-Interscience Publication New York, 1979.
4. A.V. Kiselev, V.I.Lygin. IR Spectra of Surface Compounds and Adsorbates. – Nauka, Moskow, 1972.
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