Yu. G. Bogdanova

Decomposition of cumene hydroperoxide in the systems of normal and reverse micelles formed by cationic surfactants

Decomposition of cumene hydroperoxide into free radicals in aqueous and organic media in the presence of cationic surfactants at 37°C is studied by the method of inhibitors using quercetin as an acceptor of radicals. It is found that cationic surfactants catalyze the decomposition of cumene hydroperoxide into radicals, the catalytic effect in an organic medium being higher than that in an aqueous solution. Catalytic action of surfactants greatly depends on the counterion nature. Cetyltrimethylammonium chloride has the highest catalytic activity. Characteristics of surface activity of some cationic surfactants and hydroperoxides are obtained.

Wetting of Solids by Aqueous Solutions of Surfactant Binary Mixtures: 1. Wetting of Low-Energy Surfaces

Wetting of glass by aqueous solutions of binary mixtures of cationic and nonionic surfactants was studied in the range of overall concentrations c0 = 10–8–10–2 M at the molar fraction of cationic surfactant α = 0.2, 0.5, and 0.8. It was established that the character of glass wetting is determined by the presence of cationic surfactant in the mixture: contact angle isotherms θ(c0) exhibit maximum, as in the case of individual cationic component solutions. Maximal θ values are virtually independent of the nature of cationic surfactant and its molar fraction in the mixture. It was shown that the synergistic effect in glass wetting is controlled by the chemical structure of surfactant cation.

Surface and bulk properties of aqueous binary mixtures of Pluronic F68 and low-molecular-weight cationic surfactants: 1. Surface tension and association in aqueous solutions

Surface tension of aqueous binary mixtures of Pluronic F68 and low-molecular-weight cationic surfactants is measured. The synergistic a decrease in surface tension is revealed. It is shown that this effect is controlled by the chemical structure of cationic surfactants and determined by an increased (compared to the bulk) content of Pluronic F68 in the surface layer, which is formed due to the adsorption of the individual molecules of mixture components.

Wetting effect of aqueous binary mixed solutions of cationic and nonionic surfactants

Wetting of low-energy solid surfaces (polymers, hydrophobized glass) with aqueous solutions of binary mixtures of cationic and nonionic surfactants was investigated at molar fractions of the cationic surfactant of 0.2, 0.5, and 0.8. In a narrow concentration range, the non-additive effect of wetting was observed: wetting of the solid surfaces with solutions of the mixtures is better than that would be expected from the additive behavior of the components. The magnitude of the effect depends on the surface energy of the solid substrate, total surfactant concentration in a mixture, and molar fraction of the cationic component. The wetting effect of surfactant mixtures with respect to low-energy solid surfaces can be predicted using the surface tension isotherms.

The effect of trimethylsilyl substituents in the monomer unit on the energy characteristics of surfaces of polynorbornenes obtained via metathesis polymerization

The surface properties of polynorbornenes obtained via metathesis polymerization are investigated via the wetting method. The incorporation of trimethylsilyl groups into the monomer unit causes decreases in the specific free surface energies of the investigated polymers. It is found that the dispersion terms of the specific free surface energies correlate with the free-volume and gas-permeability values of the polymers. As shown through the methods of differential scanning calorimetry and FTIR spectroscopy, during heating in air, the considered polynorbornenes undergo oxidative crosslinking, which increases their specific free surface energies. The interphase energies of crosslinked polynorbornenes are determined at their interfaces with liquids modeling polar and nonpolar phases, and the values of the work of adhesion of the crosslinked polynorbornenes to the model liquids are calculated. It is shown that the work of adhesion of the polymer to the polar phase decreases after introduction of trimethylsilyl groups, while the combination of polar and nonpolar phases give rise to an increase in the work of adhesion.

Influence of energy characteristics of the fiber-binder interface on polymer composite strength

A correlation between the energy characteristics of fiber-binder interfaces and tensile strength of polymer composite materials (PCMs) was demonstrated by the example of microplastics based on carbon fiber. A new approach for express prediction of the strength properties of PDMs based on determination of the adhesive characteristics of polymer binders in model systems by the wetting method was proposed and experimentally confirmed.

Micellar Free Radical Initiators

The effect of the nature of the surfactant, peroxide (ROOH), and medium on the rate of radical initiation in a surfactant-ROOH mixed micellar system has been studied. Cationic surfactants, as distinct from anionic and nonionic ones, have been found to catalyze ROOH decomposition to form radicals. Cationic surfactants in an organic medium exhibit higher catalytic effect than in an aqueous solution. The catalytic activity of the surfactants is strongly dependent on the counterion nature. The highest catalytic activity is shown by cetyltrimethylammonium chloride.

Simulation of the onset of flow through a PTMSP-based polymer membrane during nanofiltration of water-methanol mixture

The nanofiltration of the water-ethanol mixture of different compositions at three pressure drops through a nanoporous membrane based on poly(1-trimethylsilyl-1-propyne) has been experimentally and theoretically studied. A mathematical model of the onset of flow has been proposed, and the percolation threshold depending on the physicochemical and geometrical characteristics of the membrane system has been found. The model suggests gradual membrane pore opening with an increase in pressure and alcohol concentration in the mixture and can take account of the distribution of alcohol molecules over the cross section of the membrane pores. The theoretical results agree well with the experimental data.

Modification of polyacrylonitrile membranes by incoherent IR radiation

Polyacrylonitrile (PAN) membranes with the rejection coefficients of bovine serum albumin (Mw = 69000 Da) up to 97% have been developed. The effect of IR irradiation of PAN membranes at temperatures to 180°С has been studied for the first time. It has been found that the IR modification of the membranes at 120°С for 5 min makes PAN insoluble in a wide range of organic solvents. The test PAN membranes were obtained from PAN solutions in dimethyl sulfoxide (DMSO) with different polymer concentrations in casting solution. The morphology and filtration characteristics of the membranes are almost unaffected by the treatment. The permeability of the membranes to DMSO, dimethylformamide (DMF), dimethylacetamide (DMAA), and N-methyl-2-pyrrolidone (NMP) has been measured. It has been demonstrated that the IR-treated PAN membranes can be used for filtering the above solvents, although the initial polymer is soluble in these solvents. These membranes can also be used as supports of chemically resistant nanofiltration membranes for aprotic solvents.

Effect of lipophilicity of C60 fullerene derivatives on their ability to inhibit peroxide oxidation of lipids in aqueous medium

The aqueous solutions of C60 fullerene derivatives were studied by means of dynamic light scattering, their effect on the peroxide oxidation of lipids (POL) in aqueous solutions was investigated via chemiluminescence method. It was shown that the colloidal solubility in water, which defines the antioxidant activity of C60 fullerene derivatives during POL, is controlled by the chemical structure of the addend added to C60 fullerene. For the studied derivatives, the direct dependence of the efficiency of POL inhibition on the lipophilicity was established.