Abstract
In this work, a role of the number of free silanol groups at a nanosilica surface (specific surface area S<sub>BET</sub> = 250 m<sup>2</sup>/g, initial amount of silanols α<sub>ОН</sub> = 0.60-0.62 mmol/g) was analyzed in interaction with poly(vinyl pyrrolidone) (PVP) vs. the degree (Q<sub>TMS</sub>) of silica hydrophobization by hexamethyldisilazane at 100 <sup>o</sup>C. The value of Q<sub>TMS</sub> was 0.07, 0.42, 0.67, 0.81, 0.82, and 1.0. Adsorption of PVP onto a nanosilica surface was carried out from a water and water-ethanol (1:1) solutions of the polymer. It was shown that free silanol groups play a crucial role in the adsorption of poly(vinyl pyrrolidone). The value of the maximal adsorption (monolayer capacity) on completely hydrophobic nanosilica surface is approximately by 6.5 times lower than that for unmodified nanosilica
Highlights
Fumed high-disperse nano-scaled silica has been found a quite appropriate for creating a variety of materials with specified properties due to its characteristically large specific surface area, small size of initial nanoparticles (~10 nm), and chemical structure of a silica surface [1]
Nanosilica is widely used in various industries as a filler of polymer compositions in the manufacture of varnishes and paints, certain types of rubber, thickener of oils, etc. [1], as well as a sorbent in medicine [2]
Medicinal preparations for sorption detoxication based on nanosilica have proved to be an effective tool in the complex treatment of surgical, infectious, oncological and some other diseases [3]
Summary
Fumed high-disperse nano-scaled silica has been found a quite appropriate for creating a variety of materials with specified properties due to its characteristically large specific surface area, small size of initial nanoparticles (~10 nm), and chemical structure of a silica surface [1]. Immobilization of bio-active compounds (BAC) on a surface of nanosilica makes it possible to obtain complex medicines with new properties with respect to the nature and range of action. Some of these properties, such as pharmacokinetics, are largely determined by the structure of the surface adsorbed layer of BAC, which can be uniform or to consist of individual clusters of the molecules or ions [4]. There are different views on the nature of active surface sites with silanol groups (e.g., free or hydrogen-bound, alone or twin or vicinal) determining the sorption and chemisorption properties of silica [5]
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