A role of free silanol groups of nanosilica surface in interaction with poly(vinyl pyrrolidone)

In this work, a role of the number of free silanol groups at a nanosilica surface (specific surface area SBET = 250 m2/g, initial amount of silanols αОН = 0.60-0.62 mmol/g) was analyzed in interaction with poly(vinyl pyrrolidone) (PVP) vs. the degree (QTMS) of silica hydrophobization by hexamethyldisilazane at 100 oC. The value of QTMS 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