Vol 78, No 6 (2016)

The composition and structure of products formed on a cathode upon electrodeposition of copper from copper sulfate–poly(N-vinylpyrrolidone) mixed solutions have been studied. These products have been shown to be nanocomposites consisting of copper nanoparticles and the polymer. It has been suggested that the composite is formed by a pseudotemplate mechanism via noncovalent interaction between macromolecules and copper particles growing on the cathode. The interaction is accompanied by deceleration of subsequent growth of particles because of their screening by the polymer. This decreases the sizes of copper particles in the reaction product and the rate of metal reduction. The sonication of the reaction system yields a nanocomposite sol containing nanoparticles of copper(I) oxide. The oxide results from rapid oxidation of copper metal particles that have passed to the sol with copper(II) ions.

Kinetic regularities are studied for the air oxidation of surfactants that are widely used in the food industry, such as natural phosphatidylcholine (egg lecithin, PC) and synthetic nonionic surfactants Triton X-100 (ТХ-100), Tween 65, and Pluronic F68. Azobis(amidinopropane)-dichloride-initiated oxidation of these surfactants in an aqueous medium at 37°C develops via the chain free-radical mechanism. The chain length is equal to 5–10 units, depending on the initiator-to-surfactant concentration ratio. The rate of surfactant oxidation in an aqueous medium is proportional to the rate of radical initiation. At the same mass concentrations of the reagents, the rate of PC oxidation is several times higher than the oxidation rates of the other surfactants. The addition of TX-100 to PC liposomes decelerates the oxidation; i.e., TX-100 plays the role of an antioxidant for PC. The superposition of the oxidation rates of individual and mixed PC and TX-100 with the sizes of the microaggregates formed in their aqueous solutions shows that the antioxidation action of TX-100 is realized via the formation of a protective layer composed of its ethylene oxide groups, which shields PC liposomes from radicals, which are initiated in the bulk of an aqueous phase due to the decomposition of azobis(amidinopropane) dichloride.

Electrical conductivity of graphite dispersions in aqueous KCl solutions has been measured. The measurements have been performed in alternating- (1000 Hz) and direct-current electric fields. In an alternating-current electric field, at electrolyte concentrations of 0.0005–0.01 М, the conductivity increases as depending on the mass fraction of the dispersed phase. In 0.1 М solutions, a decrease in the conductivity of the suspension is followed by an increase at dispersed phase contents of higher than 15 wt %. In a direct-current electric field, the conductivity of graphite suspensions (0.001–0.01 М KCl) varies slightly and increases at dispersed phase contents of higher than 15 wt %. In 0.1 М solutions, the specific conductivity of the suspension initially decreases and, then, increases at dispersed phase concentrations above 15 wt %. The unusual electrical properties of the suspensions have been explained as being results of variations in the capacitive and active components of the conductivity of graphite dispersions in electrolytes within the framework of a topological model. Particle polarization and a relatively high capacitive component of the conductivity mainly contribute to an increase in the conductivity of the suspensions in 0.0005–0.01 М electrolytes in the alternating-current electric field. A decrease in the conductivity of suspensions in 0.1 М electrolytes is due to a negative difference between the capacitive and active components of the specific conductivity. It has been assumed that the aggregation of graphite particles yields conducting structures at dispersed phase concentrations above 15 wt %.

The known Schroeder paradox, i.e., a difference in the degree of swelling of ion-exchange polymers at equilibrium with liquid water and its vapor, has been discussed. It has been noted that there is no paradoxicality in this phenomenon. An example of different “swelling” based on trivial physical considerations has been presented. A simple mechanism has been proposed for increased swelling of an ion-exchange polymer immersed in liquid water, this mechanism being associated with the action of the Maxwell stresses at a polymer/electrolyte interface. The predicted values of the “excess” swelling have been shown to correspond to the data of real experiments.

Spin probe EPR spectroscopy has been employed to study the effect of a cationic monomer, trimethyl(methacryloxyethyl)ammonium methyl sulfate, on the formation, local structure, and dynamics of sodium octyl sulfate micelles in aqueous solutions. It has been established that the monomer does not affect significantly the parameters of probe rotation in micelles of this surfactant, thereby indicating a weak interaction between the studied monomer and surfactant micelles. The absence of a template effect upon monomer polymerization in micellar sodium octyl sulfate solutions, which has been confirmed by unchanged molecular-mass characteristics of obtained polymers, indicates that it is inefficient to use sodium octyl sulfate micelles as a template for radical polymerization of cationic monomers in aqueous media, in contrast to sodium dodecyl sulfate micelles studied previously.