Kolloidnyj žurnal

The Doctor Blade method was employed to obtain homogeneous, rough films comprising concentrated organosols of silver nanoparticles stabilised with bis-(2-ethylhexyl)sodium sulphosuccinate. The films exhibited a precious metal content of up to 73 at. %. The study provides a comprehensive account of the alterations in the film wetting capacity in response to the thermal treatment conditions, spanning a range of temperatures from 50 to 500°C. The evolution of the film wettability is not a linear process due to the nanoparticle sintering and thermal decomposition of stabiliser molecules. Experimental evidence indicated that the transition from non-conductive to conductive coatings (from 500 to 105 mOhm/□) was accompanied by a notable increase in the contact angle (from 25 to 78°).

Sorption of the cationic neutral red dye by Polysorb MP from a microemulsion of 0.25 mol/l AOT in n-decane was carried out at different contents of the aqueous pseudophase. The maximum sorption capacity of the sorbent in the microemulsion exceeded the corresponding one in the aqueous phase by an order of magnitude and amounted to 55 mg/g. A sharp drop in the degree of extraction with an increase in the water content of the microemulsion from 1 to 8 volume percent and the reversibility of sorption processes were demonstrated. Anionic dyes were not extracted by Polysorb MP in the same systems. With increasing water content, the zeta potential of SiO₂ particles decreased from 18 to 1 mV. Based on the obtained dependencies, a cation exchange mechanism of microemulsion sorption was proposed, including the exchange of sodium and neutral red cations between micelles adsorbed on the surface of particles and micelles in the bulk of the microemulsion.

Present paper contains the results of an experimental study of the colloidal structures and rheology of aqueous dispersions of Na⁺-montmorillonite, which were obtained by capillary and rotational viscometry methods. Aqueous dispersions of clay colloids undergo significant structural changes, accompanied by great change in the type of the flow. All these changes are managed by alteration in indifferent electrolyte concentration within a narrow concentration range. Certain critical concentration was found to appear near about 3 mM NaCl concentration for the series of dispersions with 0.25–3.0 wt% solid content. This concentration point is significantly lower than the coagulation thresholds known from the experimental and theoretical works in this field. Existence of such a critical region may reflects both processes of formation/disruption of aggregates and change in the mechanism of either aggregation or structure formation. The obtained rheological data were compared with theoretical calculations and the results of dispersion analysis (by DLS method) of aqueous dispersions which might make a bit development in the field of colloid structure investigation of smectite dispersions.

Morphological characteristics of the nanolayers of amphiphilic tert-butylthiacalix[4]crown-4-ether in cone stereoisomeric form 1 and bolaamphiphilic nitrothiacalix[4]biscrown-5-ether in 1,3-alternate form 2 deposited onto quartz substrate at varying solvent, temperature, and concentration of compounds is analyzed. Quantum-chemical calculations of the considered calix[4]arenes reveal a favorable micellar aggregation (the packing factor p < 0.3). During AFM visualization of calixarene nanolayers prepared through evaporation of solvent on substrate, spherical associates that are 200–800 nm in size are detected for compound 1, which enlarge with a decrease in the concentration of compound and an increase in solvent polarity and environmental temperature. At the same time, the dispersity of the sizes of associates increases with a decrease in temperature, but has a mixed dependence on solvent and concentration. The most uniform size distribution of spherical particles is achieved upon Langmuir monolayer formation at the air–water interface upon deposition of the solution of compound 1 in 10^–5 M solution in chloroform onto water subphase and upon vertical transfer onto substrate. In the case of bolaamphiphile 2, spherical associates are formed at t = 23°C in 10^–5 М solution in toluene and at 4°С in 10^–4 М solution in chloroform, while under other combinations of conditions, the nanofilm is represented by thread-like structures (at 23°С) and tactoid aggregates (at 4°С). Dynamic light scattering study of the solutions of amphiphile 1 in chloroform allows to detect spherical aggregates (particle size is 202 ± 92 nm), which indicates the decisive role of solvent in the formation of spherical aggregates in nanolayers, while in other cases the supramolecular organization of calixarenes is presumably affected by the interaction with substrate.