N. I. Ivanova

Synthesis of Barium Sulfate Nanoparticles in Water-in-Oil Microemulsion Systems

Micellar solutions of poly(ethylene glycol) octylphenyl ether and n-hexyl alcohol in cyclohexane were used to study the formation of water-in-oil microemulsion system and to synthesize barium sulfate nanoparticles. Barium sulfate particles (the average diameter is 10 nm) were obtained by mixing two microemulsion systems containing Ba2+and SO2–4ions. It was shown that the sizes of BaSO4particles measured by the dynamic light scattering and electron microscopy are in good agreement with each other.

Adsorption of nonionic and cationic surfactants from aqueous binary mixtures onto the solid/liquid interface

Abstract The effect of the cationic surfactant cetyltrimethylammonium bromide (CTAB) on the adsorption of the nonionic surfactant iso-nonilphenol ethoxylate with an average polyethylene oxide chain length of about 25 at the limestone/solution interface was studied. The adsorption and effect of individual and mixed solutions of surfactants on the wetting behaviour of limestone surface was also studied. The results indicated that only CTAB was adsorbed onto the limestone surface from solutions of mixture surfactants. The results also showed that hydrophobization of the solid surface occurred at a very low concentration and then, as the concentration of surfactants increased it became hydrophilic.

Adsorption of Brij 35-dodecylpyridinium bromide mixtures at air-aqueous solution and Teflon-aqueous solution interfaces

Tensiometry, spectrophotometry, the radioactive-tracer technique, and contact angle measurements are employed to study the adsorption of mixtures of a nonionic surfactant Brij 35 and a cationic surfactant dodecylpyridinium bromide (DDPB) at interfaces between their solutions and air or Teflon. It is established that adsorption layers at both of the interfaces are enriched with Brij 35. Brij 35 adsorption on Teflon is nearly independent of the presence of DDPB. On the contrary, DDPB adsorption is enhanced in the presence of Brij 35. Negative deviations from the ideal behavior are revealed for mixtures with small fractions of Brij 35 with respect to a decrease in the interfacial tension in air-solution and Teflon-solution systems.

Quantitative determination of cationic and nonionic surfactants in aqueous solutions of their mixtures by capillary zone electrophoresis

A method based on capillary zone electrophoresis is developed for a quantitative determination of cationic (dodecylpyridinium bromide) and nonionic (Triton X-100) surfactants absorbing in the UV region. The effect of the pH and ionic strength of the solution on the output time and shape of the resultant peaks is studied, and the optimal conditions of the analysis are determined. For both surfactants, the analytical signal (the area of the peak on the electrophoregram) is found to linearly depend on the concentration. It is established that the presence of a second surface-active component does not affect the signal of the surfactant analyzed; thus, surfactants may be quantitatively determined in both individual and mixed solutions. The method of capillary zone electrophoresis is shown to be applicable for determining the CMCs of surfactants.

Intermolecular interactions in the binary systems of cationic and nonionic surfactants

The micellization of the mixtures of cationic (cetyltrimethylammonium bromide, cetylpyridinium bromide) and nonionic (Triton X-100) surfactants at various content of components in aqueous solutions, as well as the adsorption of surfactants at the air/solution interface were studied. The effect of negative deviation from the ideality was discovered during the formation of mixed micelles and adsorption layers. Various theoretical approaches to the quantitative description of mixed systems were compared within the framework of the model of pseudophase separation. The parameters of intermolecular interaction in mixed micelles and adsorption layers, excess free energies of micellization and adsorption, compositions of micelles and adsorption layers were calculated. It was shown that the use of various theoretical approaches for the analysis of interactions in surfactant mixtures leads to close numerical results. It was shown that the composition of mixed micelles and adsorption layers, as well as the parameters of intermolecular interaction and the excess free energy depend on the relative content and molecular structure of surfactants (mixture components).

Adsorption and Micellization in Solutions of Dodecylpyridinium Bromide–Nonionic Surfactant Mixtures

Dependences of the surface tension of aqueous solutions of cationic (dodecylpyridinium bromide) and nonionic (Tween 80, Triton X-100) surfactants and their mixtures on total surfactant concentration and solution composition were studied. The values of critical micellization concentration (CMC) and excess free energy of adsorption were determined from tensiometric measurements. Based on Rubingh–Rosen model (approximation of the theory of regular solutions), the compositions of micelles and adsorption layers at the solution–air interface as well as parameters of interaction between the molecules of cationic and nonionic surfactants were calculated for the systems indicated above. It was established that, in the case of surfactant mixtures with considerable difference in the CMCs, the micelles of individual surfactant with lower CMC value are formed. The effect of negative deviation from the ideality during the adsorption of surfactants from mixed solutions at the solution–air interface was disclosed. It was shown that the interaction energy depends significantly on the composition of mixed systems.

Joint Solubilization of Lipophilic Drug Amlodipine and Glyceryl Monolaurate in Aqueous Micellar Solutions of Tween 80

The solubilization of lipophilic amlodipine (Am is a antihypertensive drug) and nonionic surfactant glyceryl monolaurate (GML is a skin permeation enhancer), as well as their joint solubilization (co-solubilization) have been measured by UV spectroscopy and refractometry in aqueous micellar solutions of Tween 80 (Tw). The properties of mixed micelles (Tw + GML, Tw + Am, Tw + GML + Am) have been studied, including the aggregation number of components, the localization of solubilizates, diffusion coefficients, the size and the degree of hydration. As a result of co-solubilization, (Tw + GML + Am) three-component micelles contain 4.2 times more molecules of the drug than (Tw + Am) two-component micelles. The experimental data on the kinetics of mass transfer of Am by micelles based on Tw are in good agreement with the calculations under diffusion theory; furthermore, three-component micelles carry Am more effectively than two-component micelles.

Tween 80-based mixed micelles as felodipine carriers in aqueous medium

UV spectroscopy, precise turbidimetry, and refractometry are employed to measure the solubilization of the lipophilic compounds felodipine (F) (drug) and nonionic surfactants glyceryl monooleate (GMO) and glyceryl monolaurate (GML) (efficient promoters of skin permeability (enhancers)) in aqueous solutions of Tween 80 (Tw). An increase in the concentration of Tw makes it possible to enhance the solubility of the drug by a factor of 102–103 and above as compared to F solubility in water. The effect becomes stronger in the presence of an enhancer. The following properties of Tw + F, Tw + GMO, Tw + GML, Tw + GMO + F, and Tw + GML + F micelles are studied: the aggregation numbers of the components, localization of solubilizates, diffusion coefficients, sizes, and degrees of hydration. Experimental data on the kinetics of drug mass transfer by micelles are in good agreement with the calculations performed within the framework of diffusion theory. Tw-based mixed micelles are found to be efficient carriers of F and enhancers in aqueous media, which is of importance for the creation of systems for delivery of lipophilic drugs in a bioavailable form.

Micellization and surface properties of aqueous solutions of binary mixtures of tween-80 and bromide cetyltrimethylammonium

The physicochemical properties of solutions of mixtures of cationic (cetiltrimethylammonum bromide) and nonionic (polyoxyethylene (20) sorbitan monooleate) surfactant, i.e., Tween-80, have been studied. The critical concentration of micellization, adsorption at the interface of a mixture of surfactants solution/air, and the minimum area occupied by a surfactant molecule have been determined. It was shown that, in the whole region of ratios between surfactants, sinergic effects are observed for both micellization and for the process of adsorption at the interface of a mixture of surfactants solution/air. The results obtained have been analyzed according to the regular solution theory (RST).

Contact Interactions between Individual Fibers of Cellulose and Its Derivatives: Mechanism of Cationic Surfactant Action

The effect of cationic surfactants (cetyltrimethylammonium bromide and tetrabutylammonium iodide) and cationic polyelectrolyte polyethylenimine on the coefficient of friction μ and adhesion force p(during shear and tensile testing, respectively) at the point contacts between the individual fibers of cellulose, viscose, and cellulose acetate was studied. The comparison of these data with the results of ζ-potential and adsorption measurements enabled us to relate the nonmonotonic dependence of parameters μ and pon the surfactant concentration to the changes in electrosurface properties and the hydrophilicity or hydrophobicity of the fibers. The specific free energy of interaction U[mJ/m2] was estimated for cellulose acetate fibers.