Adsorption of oligomers with various functional groups from solu-tions in xylene on titanium dioxide samples used in the domestic coatings industry

The adsorption of special additives containing different functional groups: acidic, alkaline and quaternary ammonium — from solutions in xylene was studied on samples of titanium dioxide used in the domestic coatings industry. The areas occupied by additive molecules in a dense monolayer on the TiO₂ surface are calculated. It is shown that the maximum values of adsorption are observed in the case of an additive having a basic character, and the minimum values in the case of a quaternary amine. The largest value of the main additive is explained by the presence of modifiers in TiO₂ samples — oxides of amphoteric metals (Al₂O₃, SiO₂, ZrO₂) capable of showing acid-base properties. In this case, simultaneously with the physical adsorption of the solute, chemoadsorption takes place due to strong Lewis acid centers. The smaller value of the acidic additive indicates both weak chemisorption due to weaker main centers, and a weakening of physical adsorption due to the displacement of the additive from the surface of TiO₂ by solvent molecules. In the case of quaternary amine, chemisorption is absent and only physical adsorption is observed, weakened by competing solvent adsorption, the value of which is almost the same for all TiO₂ samples. The largest amount of adsorption of basic and acidic additives is observed in the case of TiO2 samples obtained by the chloride method. In relation to the main additive, TiO2 samples of the following brands show the greatest activity: R-706, R-966, R-280, R-902, BLR-699.

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