Colloid Journal最新文献

Acrylate polymer latex and vinyl acetate-tert-carbonatepolymer latex have been widely used as waterborne coating polymers for many industrial applications. A large number of open literatures have reported on the preparation and modification of acrylate latex or vinyl acetate-tert-vinyl carbonate latex, which are synthesized with semi-continuous seeded or soap-free emulsion polymerization or other advanced emulsion polymerization technology. However, the fluorine modified BA/MMA/VAc/VeoVa10 quaternary cross-linked polymer latex has not been reported in the open literatures. In this study, butyl acrylate (BA), methyl methacrylate (MMA), vinyl acetate (VAc), tertiary vinyl carbonate (VeoVa10) are the main monomers, and sulfosuccinateethoxyether alkyl monoester disodium salt (X-40) and alkylphenolpolyoxyethylene ether (LB-407) are used as the emulsifiers. Hydroxypropylmethacrylate (HPMA) and hexafluorobutyl methacrylate (HFMA) are used as the modified monomers. Potassium persulfate (KPS) is the initiator. The fluorine modified polymer latex is prepared via the semi-continuous seeded emulsion polymerization. The structure of the latex film is characterized by Fourier transform infrared spectroscopy (FTIR). Latex films are tested by the thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and contact angle (CA). The particle size of the latex is measured with the Zetatrac dynamic light scattering instrument. The conditions for preparing the resultant latex is optimized and obtained as follows: the amount of emulsifier is 7 wt %; the amount of initiator is 0.8 wt %; the amount of HFMA is 5 wt %. The appearance of the resultant latex is translucent and blue and the average particle size of the polymer latex and its distribution are small, which is 57.89 nm and 0.048, respectively. The water contact angle increased to 95.45°. Thermal decomposition temperature of the film of the fluorine modified polymer latex is 17.33°C higher than that of the film of conventional polymer latex.

The adsorption of Cu²⁺, Zn²⁺ and Fe³⁺ ions in a ternary system on waste zeolite 4A was examined under various experimental conditions (concentration, pH, solid/liquid ratio and temperature).The physicochemical and micro-structural characterization (X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller, Fourier transform infrared spectroscopy, X-ray fluorescence, ultraviolet-visible spectroscopy and thermogravimetry/differential thermal analysis) techniques were applied. Fourier transform infrared spectroscopy was highlighted the bands characteristic of functional groups Me-(H₂O), O–H (H₂O), C–O, Me–Si–OH, Me–O and Si–OH of 4A and adsorbed by Cu²⁺, Fe³⁺ and Zn²⁺ ions (CFZ4A). The nature and coordination environment of these species were demonstrated by Ultraviolet-Visible Spectroscopy. The results show that the experimental adsorption capacities of the studied ions in the ternary system were respectively 79.125, 47.207 and 95.185 mg/g for Cu²⁺, Zn²⁺ and Fe³⁺. Temkin, Dubinin-Radushkevich and Freundlich equilibrium models give the best fit for the Cu²⁺, Zn²⁺ and Fe³⁺ ions according to R² and the minimum values of Akaike information criteria. Elovich and Double exponential kinetics models are most appropriate to describe the adsorption data of Cu²⁺ and Zn²⁺ ions and Johnson-Mehl-Avrami model describes well the Fe³⁺ ions. The increase in temperature leads to a decrease in the free energy which indicates that the reaction is spontaneous and more favorable at high temperatures. The fixation of copper, zinc and iron ions in a ternary system on the waste of commercial zeolite 4A shows certain selectivity according to the following order: Fe³⁺> Cu²⁺>Zn²⁺.

In the present paper, we report data on the influence of choice of dispersion medium-precipitating agent pair on sol–gel process for lead zirconate-titanate ceramic precursor manufacturing. Acetic acid and 2-methoxyethanol were studied as dispersion media, whereas ethylene glycol and water as respective precipitating agents. Changes in optical, rheological properties and particle size distributions during the sol–gel transition were studied at different concentrations of precipitating agents. It was shown that the nature and relative concentration of dispersion medium and precipitating agent provide wide-range control of lead zirconate-titanate sol and gel properties as well as the rate of sol–gel process, mechanism of formation and structure of the gels.

Hydrosols containing tungsten(VI) oxide nanoparticles have been studied by the electrooptical and electrophoretic methods. The influence of multivalent ions (tetravalent thorium and trivalent lanthanum cations) on the zeta-potential and polarizability of tungsten(VI) oxide particles has been determined. The dispersion dependences of the polarizability of tungsten(VI) oxide particles have been studied. A strong dependence of the electrokinetic potential and a weak dependence of the polarizability of the particles on the concentrations of thorium and lanthanum cations in the sols have been found. The polarizability of the particles is low and weakly depends on the frequency of the field polarizing the particles. This is atypical for colloidal particles, for which the thickness of the dense part of the electrical double layer is comparable with the size of molecules, while the polarization of the electrical double layer is determined by its diffuse part. The obtained results have led to a conclusion that, for tungsten(VI) oxide particles in the studied concentration range, the majority of multivalent counterions are located in the dense part of the electrical double layer due to their high adsorption potential.

The influence of small additives of Fe³⁺ ions on tetraethoxysilane hydrolysis and subsequent polycondensation of products has been studied by the viscometry and dynamic light scattering methods. Experiments have been carried out at 50°C. Hydrolysis has been carried out at pH 1.5, 2.5, 5.0, or 7.0. The amount of the dopant cations has been varied from 1.5 to 3.8 at %. In the absence of the dopant cations, the gelation time grows with increasing pH from 1.5 to 5.0, while polycondensation occurs without gelation at pH 7.0. If the dopant is added at pH 1.5, the gelation time increases, but, at pH 2.5 and 5.0, it decreases. The gelation time increases with the dopant content at all three pH values. The size of the particles formed during the polycondensation process depends on the pH and the amount of the dopant. The smallest particles with a median diameter of about 10 nm are formed at pH 2.5. It is assumed that the cause of all observed effects is the incorporation of iron cations into the siloxane matrix. The degree of the incorporation depends on the degree of iron cation hydrolysis. This assumption is confirmed by the values of the electrokinetic potential of the studied systems and the dynamics of variations in the zeta-potential with varying pH and dopant content.

A culture of human bone marrow mesenchymal stromal cells (MSCs) has been investigated. The cell culture has been grown as a monolayer in a nutrient medium containing a stabilized aqueous suspension of magnetic maghemite (γ-Fe₂O₃) nanoparticles (MNPs). The MNPs have been synthesized by the electrophysical method of laser target evaporation. A method has been proposed for stabilizing the suspension in the nutrient medium with a high ionic strength. The possibility of MNP internalization (either by fixing on the cell membrane or by incorporating into the cell space) with human MSCs has been evaluated using optical microscopy, scanning (SEM) and transmission (TEM) electron microscopy, and SQUID magnetometry. Comparative analysis of the structure and magnetic properties has been performed, and assumptions have been put forward about the features of MNP internalization with the cells in this system. It has been revealed that the limiting amount of MNPs that can be reliably analyzed in a biological sample of the studied type is about 0.005 mg. It has been found that, in the considered range of initial concentrations of magnetic nanoparticles in biological samples based on human MSCs, the level of accumulation of magnetic nanoparticles in cell cultures depends on their concentration.

The deposition of submicron aerosol particles in model filters consisting of micron-sized fibers containing radial nanowhiskers (needles) on their surfaces is considered. Numerical simulation has been performed for the transverse 3D Stokes flow field in a model filter—an isolated row of whisker-coated parallel fibers taking into account the gas slip effect on their surface. The fiber drag force and the fiber collection efficiency have been calculated as functions of the length and packing density of the whiskers and the distance between the fibers. The dependence of the fiber collection efficiency on the particle radius has been determined.

An iterative approach has been proposed for analyzing the relation between the processes of intensive evaporation and bulk condensation near an evaporation surface. This approach employs the results of the numerical solution of the Boltzmann kinetic equation for intensive evaporation from an interfacial surface to calculate the kinetics of the bulk condensation near the evaporation surface. It has been shown that, during the lifetime of the supersaturated state of the vapor predicted on the basis of the solution without condensation, the condensation aerosol has sufficient time to be formed. The results obtained indicate that the formation of droplets near the evaporation surface and the thermal effect of the condensation on the vapor parameters must be taken into account when analyzing the intensive evaporation from an interfacial surface.

The article is devoted to theoretical studying the dynamic response of ensembles of nanosized ferromagnetic particles immobilized in a nonmagnetic medium to an external field. The main attention of the work is paid to analyzing the effect of interparticle magnetic interactions on the complex magnetic susceptibility of a composite and the intensity of heat generation in it under the action of the alternating magnetic field. The analysis has shown that the dependence of the magnitude of the thermal effect on the parameter of the interparticle magnetodipole interaction is nonmonotonic and passes through a maximum. We hope that this result will help to understand the physical reason for the qualitative contradictions between the conclusions inferred in different studies devoted to the influence of the interparticle interactions on the components of the complex magnetic susceptibility of magnetic composites and the intensity of the heat generation under the action of alternating fields.

It has been shown that associates of cationic glycerolipid (CGL), rac-N-{4-[(2-ethoxy-3-octadecyloxyprop-1-yl)oxycarbonyl]butyl}-N'-methylimidazolium iodide, which has a pronounced antitumor effect, can be used for the solubilization of two hydrophobic biologically active compounds (curcumin and capsaicin) and as templates in the sol–gel synthesis of silica mesoporous container particles (MCPs). The thermodynamic characteristics of solubilization are determined, and it is shown that this process contributes to a significant increase in the solubility of both hydrophobic drugs in water. The hydrolytic condensation of tetraethoxysilane in the presence of CGL associates containing curcumin or capsaicin leads to the formation of MCPs characterized by a narrow size distribution and a high content of encapsulated drugs. This combination of the stages of the synthesis and loading of MCPs is of undoubted interest in relation to the nanoencapsulation of cationic glycerolipids (including in combination with other drugs).