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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.

Amphiphilic block and "block-like" copolymers based on poly(isobornyl acrylate) and poly(acrylic acid) were used as stabilizers for hydrophilic (titanium dioxide) and hydrophobic (copper phthalocyanine) pigments. As reflected by the dispersion stabilities and electrokinetic sonic amplitude (ESA) measurements, the molecular architecture of the copolymer is of great importance for its interaction with the pigment surface. It was observed that irrespective of polymer composition, block-like copolymers exhibit lower stabilization ability and quite different adsorption behavior in comparison to block copolymers with sharp block boundaries. Models for the adsorption behavior of both block and block-like copolymers are proposed.

In the context of the wide use of disperse systems, it is important to develop new methods for improving their quality and controllably changing their properties, including the production of aqueous suspensions of highly stable finely dispersed pigments used as components of paints and varnishes, oil and fuel additives, etc. Among the problems involved are surface phenomena; polymer adsorption on surfaces of different nature, especially in mechanical activation; and interfacial

The process of surface modification of hydrophobic organic (copper phthalocyanine (CuPc)) as well as hydrophilic inorganic pigments (titanium dioxide) in aqueous dispersions by employing tailor-made thermo-responsive copolymers and the colloidal stability have been studied as a function of temperature. The pigment surface modification is achieved by conventional adsorption and by thermoprecipitation of amphiphilic methyl vinyl ether (MVE) containing block and graft copolymers, exhibiting a lower critical solution temperature (LCST), with poly(isobutyl vinyl ether) blocks and poly(ethylene oxide) side chains, respectively. 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 electrokinetic sonic amplitude (ESA) method. The temperature-controlled sorption of PMVE-g-PEO graft copolymers on both inorganic and organic pigment surfaces 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 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.

A new type of intelligent hydrogels has been developed in the form of organic/inorganic hybrid materials by making use of the sol-gel technology. Poly(N-vinylcaprolactam) (PVCL) has been incorporated in these materials for its thermo-responsive properties. The synthesis of the hybrid hydrogels was achieved by the in situ formation of an inorganic silica phase in the presence of an aqueous solution of high molecular weight PVCL. This methodology results in the preparation of micro-heterogeneous systems in which silica particles of nanometer dimensions act as physical cross-links for the PVCL molecules. Hydrogen bonds between the remaining non-condensed silanol groups and the PVCL carbonyl functions, together with physical entanglements, are responsible for the strong interactions between the organic and inorganic phases. Stress-strain tests on hoghly swollen materials demonstrated that the unique structure of these thermo-responsive hybrid hydrogels improves the mechanical strability to a great extent as compared to conventional hydrogels. Transmission measurements demonstrate that the presence of the inorganic phase does not influence the cloud point temperatures of PVCL significantly. On the other hand, the response of the reinforced hybrid hydrogels to temperature becomes less pronounced for increasing silica fractions. The reversibility of the swelling/deswelling process has been demonstrated by swelling experiments as a function of temperature.