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The course and the result of the surface modification of titanium dioxide and ferrous oxide pigments in aqueous dispersion by ethylhydroxyethylcellulose (EHEC) without and with mechanical treatment of the dispersion by ultrasonic power was studied by the electrokinetic sonic amplitude (ESA) method. The evaluation of the ESA data showed that the ultrasonic treatment causes a significant thickness increase of the EHEC layer on the pigment which is primarily attributed to the ultrasonically induced activation of the pigment surface. The thickness of the polymer adsorption layer derived from ESA measurements was confirmed by TEM investigations. The ultrasonic treatment leads to significant changes of the adsorption layers properties and is a promising method for the surface modification of pigments with regard to dispersion stability. За допомогою електрокінетичної звукової амплітуди (ЕЗА) досліджено процес модифікації поверхні пігментів діоксиду титану та оксиду заліза у водних дисперсних системах при введенні етилгідроксиетилцелюлози (ЕГЕЦ) у відсутності та в присутності механічного оброблення дисперсних систем ультразвуком. Інтерпретацією даних ЕЗА показано, що ультразвукове оброблення викликає суттєве збільшення товщини шару ЕГЕЦ на поверхні пігментів, що пояснюється ультразвуковою активацією поверхні. Дані про товщину шарів, oтримані методом ЕЗА, підтверджені дослідженнями з використанням просвічуючої електронної мікроскопії. Ультразвукове оброблення призводить до значних змін характеристик адсорбційних шарів і є перспективним методом для модифікування поверхні пігментів та підвищення стабільності дисперсних систем.

The process of surface modification of hyd- rophobic organic pigments (copper phthalocyanine (CuPc) and carbon black) as well as a hydrophilic inorganic pigment (titanium dioxide) in aqueous dispersions by employing tailor-made thermo-responsive copolymers, and the colloidal stability have been studied. The pigment surface modification is achieved by conventional adsor- ption and by (thermo)preci pitation of amphiphilic methyl vinyl ether (MVE) containing polyvinylether block and PMVE graft copolymers with poly(ethylene oxide) side chains exhibiting a lower critical solution temperature (LCST). The effect of mechanical treatment of the pigment dispersion by ultrasonic power alone or in combination with the LCST property was investigated. The course of the pigment surface coating process was followed by the Elec- trokinetic Sonic Amplitude (ESA) method. The tempera- ture-controlled sorption of PMVE-g-PEO graft copolymers on both inorganic and organic pigment surface was investigated. It was found that ultrasonic treatment together with LCST thermoprecipitation is a promising method for the surface modification of pigments with regard to dispersion stability.

The structure of adsorption layers of amphiphilic block and block-like copolymers of poly-(isobornyl acrylate) and poly(acrylic acid) on the surface of hydrophilic titanium dioxide and hydrophobic copper phthalocyanine (CuPc) pigments in an aqueous dispersion has been studied by the electrokinetic sonic amplitude (ESA) method. The electroacoustic behaviour of the polyelectrolyte block copolymer-coated particles could be described in the context of the polymer gel layer theory. The polymer layer around the particles was found to be much thinner for CuPc as compared to the TiO 2 substrate. This is attributed to differences in the adsorption mechanism and the composition of the adsorption layer normal to the substrate surface. Adsorption models were established that consider effects of the copolymer structure.

The effect of mechanical activation of the surfaces of TiO2 and Fe2O3 inorganic pigments on the stability of their aqueous dispersions in the presence of a nontoxic water-soluble polymer, ethylhydroxyethyl cellulose (EHEC), was investigated. The mechanical activation of dispersions was performed under the action of ultrasonic field and in a laboratory disintegrator. Intense mechanical action on aqueous dispersions of TiO2 and Fe2O3 in the absence of polymer leads to their fast coagulation. In the presence of EHEC, a weak stabilizing effect was observed which was enhanced significantly upon the mechanical treatment of the dispersions. It is shown that the ultrasonic treatment of aqueous dispersions of inorganic pigments results in a significant narrowing of particle size distributions for both pigments. It is found that the interaction of EHEC with the pigment surface proceeding through the adsorption mechanism is accompanied by conformational transformations and changes in the configuration of adsorbed macromolecules. Vigorous mechanical action results in the activation of the processes of polymer adsorption on freshly formed surfaces of the pigments and in the formation of solvated adsorption layers of EHEC which determine the sedimentation stability of the systems.