Effect of sulphonic acid on the aqueous solubility of disperse dyes

Summary The solubilities of the following compounds in water andp-toluenesulphonic acid aqueous solution were determined at 5, 25 and 40 C: azobenzenep-aminoazobenzene,p-hydroxyazobenzene,p-N, N-dimethylaminoazobenzene and 1-phenylazo-4-aminonaphthalene. Prom the results the thermodynamic parameters for the transfer of one mole of the compound from water top-toluenesulphonic acid aqueous solution were calculated. It was found that the process was nearly athermal: furthermore, it was invariably accompanied by a positive unitary entropy change. The solubilizing mechanism of aromatic sulphonic acids was explained in terms of an adduct-formation with the compound to be dissolved by means of hydrophobic and nonpolarvan der Waals interactions.

---

Zusammenfassung Die Löslichkeiten folgender Verbindungen in Wasser und wÄ\rigerp-ToluolsulphonsÄure-Lösung wurden bei 5, 25 und 40 C bestimmt: Azobenzol,p-Aminoazobenzol,p-Hydroxyazobenzol,p-N,N-dimethylammoazobenzol undL-Phenylazo-4-aminonaphthalin. Aus den Ergebnissen wurden die thermodynamischen Parameter für den übergang eines Mols der Verbindung von Wasser zup-ToluolsulphonsÄurewÄ\rigen Lösungen berechnet. Es wurde gefunden, da\ die Prozesse nahezu athermisch sind. Au\erdem sind sie sÄmtlich durch eine positive und gleichmÄ\ig gro\e EntropieÄnderung begleitet. Der Lösungsmechanismus aromatischer SulphonsÄuren wird in den Begriffen einer Adduktbildung mit der Komponente erklÄrt, die durch die hydrophoben unpolarenvan-der-Waals-Wechselwirkungen entsteht.

     

Simulation of structure-related mechanical characteristics of disperse systems under dynamic conditions

Results of simulating the structure-related rheological properties of disperse systems under dynamic conditions are reported. Computer-simulation data on the influence of some parameters on the viscosity and structure-related characteristics of dispersions agree with analytical dependences and experimental results. Problems concerning the dynamic equilibrium of dispersions subjected to shear deformation, as well as disturbance of equilibrium, are considered. Results of computer simulating the percolation characteristics of dispersion microstructure under dynamic conditions are reported.     

IR spectra of aqueous disperse systems adsorbed atmospheric gases: 1. Nitrogen

Spectral characteristics of (H₂O) _i , N₂(H₂O) _i , and (N₂)₂(H₂O) _i cluster systems, where 10≤i≤50, are studied in the 0 ≤ ε ≤ 3500 cm^?1 frequency range with the molecular dynamics method on the basis of a flexible molecule model. After nitrogen is captured by an aqueous disperse system, the absorption of the IR radiation by this system increases owing to the enhancement of intramolecular vibrations. In general, the reflection of the outer IR radiation by nitrated aqueous disperse systems is attenuated; however, when the nitrogen concentration increases twofold, there is a tendency toward an increase in the fraction of reflected radiation. As the nitrogen concentration in a system of water clusters rises, the power of radiation emitted by the system increases significantly and the number of electrons interacting with the outer IR radiation decreases.     

Development of teachings of P. A. Rehbinder on surface phenomena in disperse systems

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2424–2446, October, 1990.     

IR spectra of aqueous disperse systems adsorbing atmospheric gases: 2. Argon

The absorption, reflection, and scattering of IR radiation by aqueous ultradisperse systems that absorb argon are studied with the molecular dynamics method on the basis of a flexible molecule model. Both the real and imaginary parts of dielectric permittivity are substantially increased at frequencies corresponding to intramolecular vibrations of atoms when each cluster of aqueous system adsorbs one argon atom. This effect disappears for the real part and becomes weak for the imaginary part of dielectric permittivity when there are two argon atoms added per cluster. In the region of intramolecular frequencies, the absorption coefficient of aqueous disperse systems containing argon increases as well. The reflection coefficient of the systems of water clusters that absorbed argon decreases in the frequency region of vibrations of molecules and increases in a frequency range corresponding to intramolecular vibrations. The power of radiation generated by cluster systems at the expense of thermal energy increases considerably when there is one adsorbed argon atom per cluster and decreases with a twofold increase in the number of argon atoms in clusters.     

Water-vapor plasma-based surface activation for trichlorosilane modification of PMMA

Separation rates and resolutions within capillary electrophoretic (CE) systems can be enhanced when surface zeta potentials are uniform with minimum deviations from ideal pluglike flow. Microfluidic CE devices based on poly(methyl methacrylate) (PMMA) are being developed due to the optical clarity, availability, stability, and reproducible electroosmotic flow (EOF) rates displayed by this polymer. Control of EOF in polymer-based CE systems can be achieved by surface zeta potential alteration through chemical modification. Herein, a method will be presented for the surface functionalization of PMMA with chemistry analogous to formation of trichlorosilane self-assembled monolayers on SiO2. The current method involves two separate steps. First, surface activation with water-vapor plasma introduces surface hydroxylation. Second, treatment of the plasma-treated PMMA with a substituted trichlorosilane solution forms the functional surface layer. The modified surfaces were characterized using several analytical techniques, including water contact angle, X-ray photoelectron spectroscopy, Fourier transform infrared-attenuated total reflection, secondary ion mass spectroscopy, and measurement of EOF velocities within PMMA microchannels.     

Effects of alcohols on the aqueous solubility of disperse dyes

Summary The solubility of azobenzene in water and aqueous alcohol solutions was determined at 5 °C intervals from 0° to 40 °C. Prom the results the thermodynamic parameters for the transfer of one mole of azobenzene from water to aqueous alcohol solution were calculated. It was found that the process was endothermic: furthermore, it was invariably accompanied by a positive unitary entropy change. The solubilizing mechanism of alcohols was explained in terms of an adduct-formation with the compound to be dissolved by means of hydrophobic interaction.     

Effect of mechanical activation on structural-chemical properties of phosphorites

Effect of mechanochemical activation of mono-and mid-fraction of phosphorites from the Burenkhan deposit was studied by IR and ESR spectroscopies in vibration and planetary mills. Original Russian Text ? B.G. Sukhov, D. Enkhtuyaa, Zh. Amgalan, T.I. Vakul’skaya, L.N. Novikova, Zh.G. Bazarova, B.G. Bazarov, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 6, pp. 881–886.     

Simulation of structure formation in disperse systems

The main rules governing the redistribution of microparticles in disperse systems were revealed by computer simulation. These rules predetermine the character and properties of the structure being formed, which opens up the possibility to control the properties of disperse materials, including sorbents and catalysts based on high-dispersity solid phases.     

IR absorption,reflection, and emission spectra of aqueous disperse systems interacting with nitric oxide

IR absorption, reflection, and emission spectra of aqueous disperse systems that absorbed molecules of nitric oxide are calculated. In order to reveal the effect of the absorption of NO molecules on the dielectric properties of water clusters with different sizes, clusters are divided into two groups. The first group consists of clusters containing two to ten water molecules, while the second group contains from 11 to 20 H₂O molecules. Six systems of clusters are studied, e.g., (H₂O) _n , and (NO)₂(H₂O) _n with 2 ≤ n ≤ 10 and 11 ≤ n ≤ 20 ranges. An increase in the cluster size in each group leads to the amplification of absorption, reflection, and the power of emission of IR radiation. The doubling of the NO concentration in the disperse system results in weak changes in the absorption of IR radiation, reduces the reflection and decreases the number of electrons participating in the interaction with external IR radiation, as well as significantly lowers the power of thermal radiation emitted by the system.     

Dynamics simulation of disperse systems in the presence of a structure-related mechanical barrier resulting from surfactant adsorption

A computer model has been developed to refine the notions of the kinetics of structural transformations in surfactant-modified disperse systems, the mechanism of the influence of adsorption layers on viscosity, conditions of aggregation, and evolution of nonuniformities in microstructures. Classical concepts of the structure-related mechanical barrier providing disperse systems with stability to aggregation, as well as the criterion of adsorption-layer breakdown upon interparticle collisions under dynamic conditions, have been used. It has been shown that adsorption-layer breakdown under dynamic conditions may lead to the appearance of an extreme in the viscosity curve of a disperse system. The combined effect of additives of surfactants with different molecular masses successively added to the systems has been studied via taking into account the influence of surfactant adsorption layers on the dynamics of contact interactions. The simulation results make it possible to optimize the regulation of structure-related rheological properties of dispersions so as to decrease their apparent viscosity with a simultaneous increase in the uniformity of the structure.     

Effect of surface modification on the reactivity of MCF-supported IndaBOX

MCF-immobilized indaBOX-copper complexes, which show high enantioselectivities in asymmetric Diels-Alder and cyclopropanation reactions and have reactivities strongly affected by their environment, were prepared using various linker groups and silanol capping agents.     

Fine-tuning the surface functionality of aqueous luminescent nanocrystals through surfactant bilayer modification

We report a two-step phase transfer approach to locate surfactant bilayers on water-soluble luminescent nanocrystals (NCs), through which the surface functionality of the NCs is tunable. Since the species of both inner and outer surfactants of the bilayer are alterable in wide range, the current effort provides a facile approach to anchor various functional groups on aqueous NCs. The primary results indicate that these bilayer-modified NCs are able to be incorporated with various organic and inorganic materials.     

Adsorption of polymethacrylic acid from aqueous solutions on disperse titanium dioxide

The state of macromolecules of polymethacrylic acid adsorbed on the surface of disperse titanium dioxide was assessed using a combination of the differential concentration approach to the determination of adsorption and methods for determining the size of disperse adsorbents by dynamic light scattering and sedimentation analysis in the field of centrifugal forces. Three sections were found on the isotherm of adsorption: in the first, isolated islands of adsorbed macromolecules formed; in the second, layers of macromolecules with a different degree of deformation were observed; in the third, determining the adsorption of macromolecules is complicated by other accompanying processes, and assessing the state of macromolecules in the adsorption layer becomes difficult.