A. A. Dyshin

Dispersion of single-walled carbon nanotubes in alcohol-cholic acid mixtures

A procedure for dispersing single-walled carbon nanotubes (SWNTs) for the preparation of suspensions with high concentrations of individual nanotubes in various solvents was described. The most stable suspensions were obtained from a mixture of ethanol with cholic acid at an acid concentration of 0.018 mol/kg.

Dissolution of single-walled carbon nanotubes in alkanol-cholic acid mixtures

A procedure for dispersing the single-walled carbon nanotubes (SWCNTs) for preparing stable suspensions with high concentrations of individual nanotubes in various alcohols was described. The obtained suspensions were studied by Raman spectroscopy. The solubility of the single-walled carbon nanotubes in alcohols was found to depend on the concentration of cholic acid. The ethanol-surfactant mixture was shown to be the best solvent for all alkanol-cholic acid mixtures (0.018 mol/kg) under study used for preparing time-stable suspensions of single-walled carbon nanotubes. The dissolving ability of aliphatic alcohols was found to decrease in the series: ethanol-isopropanol-tert-butanol-butanol-propanol.

The volume characteristics and molecular dynamics simulation of nonaqueous solutions of aliphatic alcohols

The kinematic and thermodynamic characteristics of the methanol-heptane system were calculated by the molecular dynamics method at 300 K and heptane concentrations up to 0.095 mole fractions. An increase in the concentration of heptane was shown to stabilize the structure of methanol. The densities of aliphatic alcohol-alkane-electrolyte (nonelectrolyte) systems were measured experimentally at 298.15 K. The results were used to calculate apparent and partial molar volumes with errors of 0.01 cm3/mol. The dependences of volume properties on composition contained extrema in agreement with theoretical calculations.

Density and viscosity of methanol-heptane (octane) mixtures at low alkane concentrations over the temperature range 288.15–328.15 K

An Anton Paar 4500 densimeter was used to measure the density of methanol-heptane and methanol-octane solutions in the region of low alkane concentrations over the temperature range 288.15–328.15 K. The experimental data were used to calculate the apparent, partial, and excess molar volumes of alkanes. Viscosity was measured with an Ubbelohde viscometer at 298.15 K. The NMR spectra were recorded on a Bruker Avance III BioSpin spectrometer. The physicochemical characteristics of methanol-heptane and methanol-octane mixtures were considered in combination with molecular dynamics simulation results. The conclusion was drawn that methanol was structured in mixtures with heptane at concentrations of 0.04–0.06 alkane mole fractions. This peculiarity was not observed in mixtures with other alkanes.

Topology of hydrogen-bonded clusters in sub- and supercritical n-buthanol. Molecular dynamics simulation

We present the study of hydrogen-bonded clusters in sub- and supercritical n-buthanol by molecular dynamics. A number of characteristics of hydrogen bonds were calculated on the basis of a geometrical criterion. It was determined that the effect of the partial reduction of the structure of condensed medium near critical point is manifested in an increase in the average number of hydrogen bonds and the first peak of the hydrogen-oxygen radial distribution function. By investigating the topology of hydrogen-bonded clusters, it was shown that this reduction is determined by an increase of the fraction of molecules bound by two hydrogen bonds, and a reduction in the fraction of unbonded ones.

A volumetric investigation of solvophobic effects in halide-n-alkanol-n-alkane ternary systems

The density of solutions in the methanol-heptane-sodium chloride and ethanol-octane-lithium chloride systems was measured at 298.15 K using a vibratory densimeter. From the experimental data, apparent and partial molar volumes were calculated accurate to 0.01 cm3/mol. It was shown that volume properties versus composition dependences behave extremely. This behavior was attributed to restructuring of the solutions, namely, to a closer packing of molecules of the alkanol-alkane mixed solvent at an alcohol mole fraction of 0.95. It was shown that, for larger hydrocarbon residues in both components of the mixed solvent, the extremum in the volume properties does not disappear and holds its position.

Dependence of Bulk and Viscosity Characteristics of Naphthalene Solutions in Methanol-Heptane Mixtures at 298.15 K

The solubility of naphthalene in methanol-heptane mixtures is studied according to isothermal saturation. Data on the density of solutions and partial and apparent molar volumes of naphthalene are obtained. Viscosity is determined using an Ubbelohde viscometer with a suspended level equipped with photoelectric circuit for flow time measurement. All measurements are performed at 298.15 K. Our results are discussed on the basis of interactions that occur in solution.

The volume characteristics of solution of naphthalene in heptane-ethanol mixtures at 298.15 K

The solubility of naphthalene was studied by the isothermal saturation method, and the density of naphthalene-heptane-ethanol solutions at 298.15 K was measured using an oscillating tube densimeter. The results were used to calculate the volume characteristics of naphthalene in the systems specified. The solubility of naphthalene in heptane was substantially higher than in ethanol. The composition dependences of apparent partial molar volumes contained extrema. The reason for such nonlinear dependences can be a sharp change in the contribution to the entropy of mixing related to the packing of molecules of different diameters (naphthalene and heptane). Another possible mechanism of these anomalies can be related to the stabilization of the structure of alkanols in the solvation sheath of alkanes noticed earlier.

Dispersion of single-walled carbon nanotubes in dimethylacetamide and a dimethylacetamide–cholic acid mixture

A way of dispersing single-walled carbon nanotubes in preparing stable suspensions with high concentrations of individual nanotubes in amide solvents is described. The obtained suspensions are studied via Raman spectroscopy. The dependence of the degree of single-walled carbon nanotube (SWNT) dispersion in individual and mixed amide solvents on the type of solvent, the mass of nanotubes, and the concentration of cholic acid is established. A technique for processing spectral data to estimate the diameters and chiralities of individual nanotubes in suspension is described in detail.

Dependence of the volume characteristics and viscosity of solutions of methanol-octane-naphthalene on composition at 25°C

The limiting solubility of naphthalene in a mixture of methanol-octane at 25°C is determined via isothermal saturation. The kinematic viscosity of a mixture of methanol-octane-naphthalene is measured at 25°C. Data on the density of triple mixtures of methanol-octane-naphthalene, used to calculate the partial and apparent molar volumes of naphthalene, are obtained with a high degree of accuracy. The obtained results are discussed in terms of the interactions that occur in solution.