Kinetics of growth of chain aggregates in magnetic suspensions

Theoretical study of the kinetics of the growth of chain aggregates in suspensions of magnetizing non-Brownian particles is performed. An analytical model for calculating the time-dependent distribution function over the number of particles in the chains is developed and computer experiments on the kinetics of the aggregation of these particles are carried out. Results of calculations using an analytical model are in good agreement with the data of computer experiments when the volume concentration of particles is in the range of 1–2%, which corresponds to many modern magnetorheological suspensions. This allows us to recommend the developed mathematical model as a basis for describing kinetic phenomena in magnetorheological suspensions with low or moderate particle concentrations.     

Fischer–Tropsch synthesis over CNT-supported cobalt catalyst: effect of magnetic field

In the present work, the cobalt catalysts supported on carbon nanotubes (CNTs) were prepared by impregnation method in the presence and absence of magnetic field. The prepared catalysts were employed to yield higher hydrocarbons via Fischer–Tropsch synthesis. It is explored that using magnetized water can effectively change the catalyst geometry in impregnation catalyst preparation method. For the preparation of different sizes of cobalt particles on the CNTs support, the physical properties of solvent (water) in impregnation process were changed using the magnetizing process. The results showed that the average particle sizes of impregnated cobalt nanoparticles were decreased by using magnetized water in impregnation step. In addition, in the magnetized treated cobalt catalyst, the cobalt particles mostly dispersed outside the tubes because the capillary forces decreased by reducing water surface tension. Furthermore, the experimental results showed that the probability of chain growth (α) and selectivity to heavier hydrocarbons increased in magnetized water treatment catalysts.     

The effect of the t-butyl substituent on polymer properties in homopolymer systems

The effect of a bulky substituent on properties of different homopolymers has been examined. The substituent is the t-butyl moiety attached to a benzene ring found in the repeat units of the homopolymers of polyesters, polyarylates, polyamides, and polyaramides. These polymers have been prepared by melt, solution, or interfacial techniques. The source of the t-butyl group is mainly from 5-t-butylisophthalic acid (5TBIA) and comparisons are generally made with corresponding homopolymers based on isophthalic acid. The effect of the t-butyl group is shown by comparison of the properties of these homopolymers. Thermal and mechanical (tensile and impact) properties, density, water absorption, solubility, and processability are discussed. Differences in these properties are attributed to the t-butyl group and are based on intermolecular and intramolecular interactions that include increased free volume, chain stiffening, and conformational changes.     

The Calorimetric and Volumetric Properties of Selected α-Amino Acids and α,ω-Amino Acids in Water at T = (288.15, 298.15, 313.15, and 328.15) K and p = 0.1 MPa

Relative densities and relative massic heat capacities have been measured for the amino acids β-alanine, 4-aminobutanoic acid, d,l-norleucine and d,l-norvaline in dilute aqueous solution at p = 0.1 MPa and T = (288.15, 298.15, 313.15 and 328.15) K. Apparent molar volumes and apparent molar heat capacities have been calculated and the isothermal concentration dependences of these properties have been modeled to yield apparent molar properties at infinite dilution. Values for apparent molar properties at infinite dilution are compared to those previously reported in the literature. Trends in the temperature dependences of the infinite dilution properties are discussed in terms of methylene group contributions and the variations in these contributions caused by the presence of ionic end groups.     

Quaternary Ammonium Polyelectrolytes. V. Amination Studies of Chloromethylated Polystyrene with N,N-Dimethylalkylamines

The amination reactions of chloromethylated polystyrene with N,N-dimethyldodecylamine, N,N-dimethyltetradecylamine, and N,N-dimethylhexadecylamine were studied. The physical properties, particularly the solubility properties of the resulting polymers, are influenced by the hydrophobic properties of the long alkyl chain on the N⁺ atoms. The main factor that influences the kinetics of the reactions is the polymersolvent interaction parameter.     

Analysis of thermodynamic properties and phase equilibria in the Si-P system

A self-consistent analysis of the available data on thermodynamic properties and phase equilibria in the Si-P system is performed. Thermodynamic properties of solid and liquid solutions of phosphorus in silicon are approximated on the basis of the concepts of dilute and ideal associated solutions. The thermodynamic properties and phase boundaries in the range of compositions 0 ≤ x(P) ≤ 0.5 are adequately described.     

Electronic Structures and Optical Properties of Ga Doped Single-Layer Indium Nitride

Electronic structures and optical properties of single-layer In_1-xGa_xN are studied by employing Heyd-Scuseria-Ernzerh (HSE) method based on the first-principles. The band structure and density of states (DOS) of single-layer In_1-xGa_xN are calculated, and the band gap ranges from 1.8 eV to 3.8 eV as the ratio x changes, illustrating the potential for the tunability of band gap values via Ga doped. We also have investigated optical properties of single-layer In_1-xGa_xN such as dielectric function, refractive index and absorption coefficient, the main peak of dielectric function spectrum and the absorption edge are found to have a remarkable blue-shift as the concentration of Ga increases. Furthermore, the optical properties of single-layer In_1-xGa_xN are analyzed based on the band structures and DOS analysis. Such unique optical properties have profound application in nanoelectronics and optical devices.     

Thermodynamics of carbyne

Published data on the thermodynamic properties of carbyne are analyzed and generalized. The thermodynamic properties of carbyne are compared with the properties of other allotropic modifications of carbon (fullerenes, diamonds, and graphite). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 971–980, June, 2000.     

Liquid Structure and Thermodynamics of Alkane Mixtures

Spectroscopic investigations and light scattering experiments with saturated, liquid hydrocarbons and their mixtures indicate a specific and distinct influence of the constitution, conformation, and flexibility of the molecule on the structure and macroscopic behavior of such liquids. Orientational order present in pure liquid n-alkanes, for example, characteristically affects the thermodynamic mixing properties, such as the enthalpy of mixing ΔH_M and the entropy of mixing ΔS_M , when these liquids are mixed with each other, or with other liquids. Nowadays it is possible to determine thermodynamic mixing properties experimentally with such precision that systematic investigations of these properties allow the behavior of liquids to be studied qualitatively and–with molecular theories of liquids–to some extent also quantitatively. The latest results in this respect, exemplified by mixtures of alkanes, are discussed. These results not only demonstrate the progress made in understanding the relations between molecular (microscopic) and macroscopic properties, but are also of importance for industrial applications (e.g. separation processes) in which mixtures of hydrocarbons are involved.     

Thermochemistry of electrolyte solutions

The results of calorimetric investigations of electrolyte solutions in the mixtures of water, methanol, N,N-dimethylformamide, and acetonitrile with numerous organic cosolvents are discussed with regard to the intermolecular interactions that occur in the solution. Particular attention is given to answer the questions how and to what extent the properties of the systems examined are modified by the cosolvent added and how much the properties of the cosolvent are revealed in the mixtures with the solvents mentioned above. To this goal, the analysis of the electrolyte dissolution enthalpies, single ionic transfer enthalpies, and enthalpic pair interaction coefficients as well as the preferential solvation (PS) model are applied. The analysis performed shows that in the case of the dissolution enthalpies of simple inorganic electrolytes in water–organic solvent mixtures, the shape of the dependence of the standard dissolution enthalpy on the mixed solvent composition reflects to a large extent the hydrophobic properties of the organic cosolvent. In the mixtures of methanol with organic cosolvents, the ions are preferentially solvated either by methanol molecules or by molecules of the cosolvent, depending on the properties of the mixed solvent components. The behavior of inorganic salts in the mixtures containing N,N-dimethylformamide is mostly influenced by the DMF which is a relatively strongly ion solvating solvent, whereas in acetonitrile mixtures, the thermochemical behavior of electrolyte solutions is influenced to a large extent by the properties of the cosolvent particularly due to the PS of cation by the cosolvent molecules.     

Recent research progress in the synthesis,properties and applications of ferrocene‐based derivatives and polymers with azobenzene

Aromatic azobenzene derivatives are outstanding organic photochromic compounds that possess unique photochemical properties. These compounds are widely used in research and development for various applications, especially in information storage, owing to their ability to isomerize between cis (Z) and trans (E) forms under the influence of light of different wavelengths. On account of these advantages, many efforts have been made to generalize the use of azobenzene derivatives. Furthermore, ferrocene‐based polymers and derivatives are promising candidates for functional materials due to their unique redox properties. By interlinking ferrocene with azobenzene, novel functional materials can be obtained that will integrate the excellent properties of both and will provide new applications in various fields including information storage, ion recognition, molecular devices, etc. This article provides an overview of the synthesis, properties and applications of novel ferrocene‐based polymers and derivatives containing azobenzene units. Copyright © 2015 John Wiley & Sons, Ltd.     

Enthalpies of solution of <Emphasis Type="Italic">n</Emphasis>-alkanes in mixtures of MeCN with alkan-1-ols at 298.15 K. Relations between the thermodynamic properties of binary and ternary systems

The solution enthalpies of n-hexane, n-nonane, and n-undecane in mixtures of MeCN with EtOH, PrOH, and BuOH were determined by calorimetric method at 298.15 K. Relations between the thermodynamic properties of ternary systems and the properties of the binary solvents and the solute are discussed. To predict the enthalpies of solution of hydrocarbons in mixed solvents whose components have strongly different molar volumes (V ₂/V ₁ > 1.5), it is proposed to use the values that are additive in the volume fraction scale. The solution enthalpies of hydrocarbons in mixtures characterized by close molar volumes of the components strongly depend on the excess properties of the binary solvent.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1578–1582, August, 2004.     

Remarkable Size Effect on Photophysical and Nonlinear Optical Properties of All-Carboatomic Rings,Cyclo[18]carbon and Its Analogues

Inspired by recent experimental observation of molecular morphology and theoretical predictions of multiple properties of cyclo[18]carbon, we systematically studied the photophysical and nonlinear optical properties of cyclo[2N]carbons (N=3–15) allotropes through density functional theory. This work unveils the unusual optical properties of the sp-hybridized carbon rings with different sizes. The remarkable size dependence of the optical properties of these systems and their underlying nature are profoundly explored, and the relevance between aromaticity and optical properties are highlighted. The extrapolation curves fitted for energy level of frontier molecular orbitals, maximum absorption wavelength, and (hyper)polarizability of considered carbon rings are presented, which can be used to reliably predict corresponding properties for arbitrarily large carbon rings. The findings in this study will facilitate the exploration of potential application of cyclocarbons in the field of optical materials.     

Theoretical study of the effect of counterions on the structure of pyrrole oligomers

The influence of counterions on the calculated properties of positively charged pyrrole oligomers is studied using the semiempirical AM1 and PM3 methods. The geometry and properties of the charged pyrrole oligomers are significantly affected by counteranions both in anti and syn conformations. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem 88: 296–301, 2002     

Liquid crystalline behaviour of mixtures of structurally dissimilar mesogens in binary systems

We have studied four binary systems comprising four ester components, viz. 4-nitrophenyl-4′-n-alkoxybenzoates (wheren-alkoxy isn-butoxy, C₄,n-hexyloxy, C₆,n-octyloxy, C₈ andn-decyloxy, C₁₀) and one azo component, 4-n-decyloxy phenylazo-4′-isoamyloxy benzene. A variety of mesomorphic properties are observed in these mixtures. The properties of these systems are discussed on the basis of phase diagrams.     

The synthesis and solution properties of some rigid-chain,water-soluble polymers: Poly[N,N′-(sulfo-phenylene)phthalamide]s and poly[N,N′-(sulfo-p-phenylene)pyromellitimide]

Poly[N,N′-(sulfo-phenylene)phthalamid]es and poly[N,N′-(sulfo-p-phenylene)pyromellitimide] were prepared in water-soluble form and were found to have unique solution properties, similar in some respects to xanthan. The polymer most investigated, poly[N,N′-(sulfo-p-phenylene)terephthalamide] (PPT-S), is produced as the dimethylacetamide (DMAC) salt by the solution polymerization of 2,5-diaminobenzenesulfonic acid with terephthaloyl chloride in DMAC containing LiCl. The isolated polymer requires heating in water to dissolve; the resulting cooled solutions are viscous or gels at concentrations as low as 0.4%. They are highly birefringent, exhibit circular dichroism properties, and are viscosity-sensitive to salt. Solutions of this polymer mixed with those of guar or hydroxyethyl cellulose give significantly enhanced viscosity. The polymer is relatively low molecular weight, ca. 5000 estimated from viscosity data. Some meta and para isomeric analogs of PPT-S were prepared; these polymers have similar properties except they are more soluble in water, and higher concentrations are required to obtain significant viscosity. Poly[N,N′-(sulfo-p-phenylene) pyromellitimide] (PIM-S) was prepared similarly from 2,5-diaminobenzenesulfonic acid and pyromellitic dianhydride. Its aqueous solution properties are similar to those of PPT-S. It appears that these relatively low-molecular-weight rigid-chain polymers associate in water to form a network that results in viscous solutions at low concentrations.     

Density functional finite cluster method for polarizability of large BeN three‐dimensional systems

The structures and the properties of small clusters are known to be quite different from those of the bulk material. Consequently, the focus of most studies is towards understanding the changes in electronic properties with increasing cluster size. Linear static electronic dipole polarizabilities of the Be_N (N→∞) solid are obtained at the DFT(PWB91) level by extrapolation of ab initio calculations on Be_N (N=1,…,132) clusters. For the mean polarizability, a [5s3p] basis set is shown to give accurate values if the tri‐periodic clusters are big enough. No calculation has yet been carried out on Be_N (N→∞), but it is clear that these linear properties converge relatively slowly with cluster size. For Be_N, cluster size up to N=90 atoms are sufficient to give limiting infinite solid polarizabilities with relatively small uncertainties. For N=132, the mean polarizability result is probably very accurate. These results suggest that DFT is a good method for the determination of these properties. © 2000 John Wiley & Sons, Inc. J Comput Chem 22: 230–240, 2001     

Thermophysical properties of the ternary mixture ethanol + n-hexane + n-octane in function of the temperature

This article presents the analysis of the following physical properties such as refractive indices, excess molar volumes, sound velocity and the temperature dependence of the ternary system ethanol?+?n-hexane?+?n-octane in the temperature range 288.15–323.15?K at atmospheric pressure. The derived properties are calculated from data obtained experimentally and fitted to Cibulka equation.     

Basis set quality. II. Information theoretic appraisal of various s- orbitals

The expectation values 〈r^k〉 (?2 ? k ? 4, k = 10), values of the charge density ρ(r) at selected points, and coefficients in the MacLaurin expansion of ρ(r) are used to test the quality of 71 orbital basis sets used for the atomic helium Hartree–Fock problem. These tests in position space are complementary to the momentum space tests previously carried out [Int. J. Quantum Chem. 21 , 419 (1982)]. Information theoretic measures with respect to either or both position and momentum space properties are subsequently defined and the orbitals are ranked accordingly. These measures indicate that, for a given orbital, momentum space properties are more poorly predicted than position space ones. Moreover an improvement in the virial ratio does not necessarily lead to a more balanced orbital with respect to position and momentum space properties. Basis sets containing Slater-type orbitals are again found to be rather accurate. The exponentially damped rational function is confirmed to be the outstanding two-parameter unconventional orbital.     

Optoelectronic Properties of Carbon-Bound Boron Difluoride Hydrazone Dimers

The creation of dimeric boron difluoride complexes of chelating N-donor ligands is a proven strategy for the enhancement of the optoelectronic properties of fluorescent dyes. We report dimers based on the boron difluoride hydrazone (BODIHY) framework, which offer unique and sometimes unexpected substituent-dependent absorption, emission, and electrochemical properties. BODIHY dimers have low-energy absorption bands (λ_max=421 to 479 nm, ϵ=17 200 to 39 900 m ⁻¹ cm⁻¹) that are red-shifted relative to monomeric analogues. THF solutions of these dimers exhibit aggregation-induced emission upon addition of water, with emission enhancement factors ranging from 5 to 18. Thin films of BODIHY dimers are weakly emissive as a result of the inner-filter effect, attributed to intermolecular π-type interactions. BODIHY dimers are redox-active and display two one-electron oxidation and two one-electron reduction waves that strongly depend on the N-aryl substituents. These properties are rationalized using density-functional theory calculations and X-ray crystallography experiments.