Peroxide-initiated crosslinking of maleic anhydride-modified low-molecular-weight polybutadiene. II. Crosslinking degree and thermal degradation of cured polymers

The crosslinking density and thermal properties of peroxide-crosslinked low-molecular-weight polybutadiene and its modification products with maleic anhydride were studied. It was shown that the Flory-Rehner equation may be used for describing the equilibrium swelling of the studied systems. The molecular weight between crosslinks calculated from this equation has values from 117 to 216. It was found thermogravimetrically that the thermal stability of modified polybutadiene is lower than the unmodified material. The thermal destruction of the polymers studied is a step-by-step reaction, the first being of zero order, with activation energy of 76.6–112.6 kJ/mole, the second, a first-order reaction with an E_a of 286.8–363.4 kJ/mole.     

Kinetics and mechanism of quaternization of tertiary phosphines with unsaturated carboxylic acids. Kinetic studies of the reactions in aprotic solvents

Data obtained while studying the kinetics of quaternization of tertiary phosphines with the unsaturated carboxylic acids in the series of aprotic solvents indicate the participation of a second molecule of acid playing the part of the external proton donor in this process. Quantitative analysis of the effect of solvent within the frames of the Koppel-Palm equation showed that the main contribution in the reaction rate belongs to the nucleophilicity of medium while the effects of polarity and electrophilicity are smaller. The results obtained suggest the step-by-step mechanism of interaction including the formation of the zwitterionic intermediate on the reaction pathway common for the solvents with different proton activity.     

近红外光谱法分析格列齐特片

应用化学计量法处理光谱数据,用偏最小二乘法建立格列齐特片的近红外分析模型。通过光谱预处理和模型的逐步优化最终确定定量分析模型的相关系数为0.991,交叉验证均方差(RMSECV)为0.641,预测均方根误差(RMSEP)为0.980,主因子数为4。选取15个验证样品对模型进行检验,检测结果相对误差在-2.04%～3.52%之间。     

Transcorrelated calculations of homogeneous electron gases

We have constructed the complete transcorrelated equation for homogeneous electron gases and investigated this equation on two- and three-dimensional systems. Correct asymptotic behaviours of the correlation factors can be easily obtained from the transcorrelated equation, both the long-range RPA type decay and the short-range spin dependent cusp conditions. The complete transcorrelated equation is solved numerically and the outcome correlation energies agree very well with variational quantum Monte Carlo results. Possible simplifications of the transcorrelated calculations are discussed, where we find that the RPA equation for the correlation factor can be considerably improved by adding one more term in the equation.     

The modified Hartree–Fock self-consistent field equation

A one-electron correlation operator is introduced into the Hartree–Fock self-consistent field equation. The correlation operator is derived from the second-order perturbation theory. Energies of atomic and molecular systems calculated from this modified Hartree–Fock equation are equal to that from second-order perturbation of Hartree–Fock equation. The modified equation can also be solved self-consistently by the LCAO approximation. We also presented the modified expressions for other operators.     

A new equation for correlation of vapour-liquid equilibrium data of strongly non-ideal mixtures

A new equation for correlation of the thermodynamic excess functions of mixing, based on considerations of geometrical shape is proposed. Use of this equation for the correlation of heat of mixing data and vapour-liquid equilibrium data is proposed. The possibility of predicting multicomponent vapour-liquid equilibrium from binary data by using the proposed equation is shown. The equation is especially useful for correlating the excess functions of strongly non-ideal systems and for checking thermodynamic consistency of vapour-liquid equilibrium data.     

Structure-Property Correlation Equation: IV. Estimation of the Logarithm of the Distribution Factor of Flexible Hydrocarbon Molecules in the Octanol-Water System

A simple structure-property correlation equation was suggested for estimating the distribution factors of compounds in the octanol-water system. The ways of taking into account the conformational features of molecules are discussed. The parameters of the correlation equation are determined from a limited set of test examples.     

Surface tension and density of binary mixtures of monoalcohols,water and acetonitrile: equation of correlation of the surface tension

Measurements of the surface tension (σ) and density (ρ) of binary mixtures of monoalcohols, water and acetonitrile at 298.15 K and at atmospheric pressure, as a function of mole fraction (x) have been made. The experimental values of the deviation of surface tension and the excess of molar volume (Δσ, V ^E) have been correlated by the Redlich–Kister equation. An empirical correlation equation is presented for the study of the surface tension of these mixtures, and comparisons are made of the experimental values of surface tension versus those obtained with the correlation equation and with other models of correlation. Finally, with the purpose of corroborating the validity of the correlation equation, the latter is applied to other reference binary mixtures.     

Compensation effect and isokinetic temperature in thermal dissociation reactions of the type Asolid ⇌ Bsolid + Cgas

It is shown that the Zawadzki — Bretsznajder rule, compensation effect, and isokinetic temperature are simple consequences of interpretation of the Arrhenius equation as a projection correlation. It is established that such an interpretation of the Arrhenius equation allows the discrimination of the deviation factors which impart a definite (although not always simple and recognized) physical sense, to the known empirical correlation. A possibility of deriving new correlation relationships by this method of reasoning is presented.     

Application of the perturbed Lennard–Jones chain equation of state to solute solubility in supercritical carbon dioxide

The perturbed Lennard–Jones chain (PLJC) equation of state is a thermodynamic model based on the perturbation theory of liquid state. This equation has been shown in the past to be a successful model for phase equilibria calculations of binary and ternary fluid mixtures and polymer solutions. In this work, we employed for the first time the PLJC equation to model the solubility of 39 solids in supercritical carbon dioxide. It was shown that the model achieves good correlation with three temperature independent parameters. A comparison of the PLJC with the commonly used Peng–Robinson equation reveals the PLJC equation gives better correlation to the solubility data than the Peng–Robinson model that utilizes temperature dependent parameters.     

An interaction site model integral equation study of molecular fluids explicitly considering the molecular orientation

We implemented an interaction site model integral equation for rigid molecules based on a density-functional theory where the molecular orientation is explicitly considered. In this implementation of the integral equation, multiple integral of the degree of freedom of the molecular orientation is performed using efficient quadrature methods, so that the site-site pair correlation functions are evaluated exactly in the limit of low density. We apply this method to Cl(2), HCl, and H(2)O molecular fluids that have been investigated by several integral equation studies using various models. The site-site pair correlation functions obtained from the integral equation are in good agreement with the one from a simulation of these molecules. Rotational invariant coefficients, which characterize the microscopic structure of molecular fluids, are determined from the integral equation and the simulation in order to investigate the accuracy of the integral equation.     

An Equation for the Correlation of Viscosities of Binary Mixtures

Knowledge of the viscosity of binary mixtures is of great importance in many industrial processes. Rarely can the viscosity of mixtures be obtained from the sum of the viscosities of the pure components. The theoretical study of the viscosity of mixtures is generally complicated. Numerous empirical correlation models have been proposed. The present study proposes a new empirical correlation equation, based on lineal behavior. The equation can easily be used with one, two or three parameters, and in many cases it improves upon the models that are commonly used. Likewise, the excess viscosity calculated with the proposed equation generally yield more satisfactory results than those obtained with the polynomial equation of Redlich-Kister.     

An integral equation theory for inhomogeneous molecular fluids: the reference interaction site model approach

An integral equation theory which is applicable to inhomogeneous molecular liquids is proposed. The "inhomogeneous reference interaction site model (RISM)" equation derived here is a natural extension of the RISM equation to inhomogeneous systems. This theory makes it possible to calculate the pair correlation function between two molecules which are located at different density regions. We also propose approximations concerning the closure relation and the intramolecular susceptibility of inhomogeneous molecular liquids. As a preliminary application of the theory, the hydration structure around an ion is investigated. Lithium, sodium, and potassium cations are chosen as the solute. Using the Percus trick, the local density of solvent around an ion is expressed in terms of the solute-solvent pair correlation function calculated from the RISM theory. We then analyze the hydration structure around an ion through the triplet correlation function which is defined with the inhomogeneous pair correlation function and the local density of the solvent. The results of the triplet correlation functions for cations indicate that the thermal fluctuation of the hydration shell is closely related to the size of the solute ion. The triplet correlation function from the present theory is also compared with that from the Kirkwood superposition approximation, which substitutes the inhomogeneous pair correlation by the homogeneous one. For the lithium ion, the behavior of the triplet correlation functions from the present theory shows marked differences from the one calculated within the Kirkwood approximation.     

Measurement and correlation of the solubility of 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) in different solvents

A knowledge of the solubility of 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) in different solvents is essential for crystallization and further theoretical studies. The laser monitoring system was used for measuring the solubility of DNTF in methanol, ethanol, acetic acid, benzene, toluene and n-butanol at temperatures ranging from (298.15 to 338.15) K. Polynomial empirical equation, ideal model and modified Apelblat equation were used to correlate the experimental values. The correlated results of three correlation equations present good consistency with the experimental values. In addition, the modified Apelblat equation produced higher accuracy than the polynomial empirical equation and the ideal equation. The standard dissolution enthalpy, standard dissolution entropy and the Gibbs energy were calculated from the experimental values. The solubility values of DNTF and correlation equations from this experiment would be invoked as basic data and models regarding the crystallization process of DNTF.     

Statistical theory for hydrogen bonding fluid system of AaDd type (Ⅲ): Equation of state and fluctuations

The equation of the state of the hydrogen bonding fluid system of AaDd type is studied by the principle of statistical mechanics. The influences of hydrogen bonds on the equation of state of the system are obtained based on the change in volume due to hydrogen bonds. Moreover, the number density fluctuations of both molecules and hydrogen bonds as well as their spatial correlation property are investigated. Furthermore, an equation describing relation between the number density correlation function of "molecules-hydrogen bonds" and that of molecules and hydrogen bonds is derived. As application,taking the van der Waals hydrogen bonding fluid as an example, we considered the effect of hydrogen bonds on its relevant statistical properties.     

New approach to the correlation problem: Electron interaction potential as a variable in solving the many-particle Schrödinger equation

The many-electron wave function is represented as the product of the wave function of the independent particles and the function that depends only on the value of the interelectron interaction potential. The function defines the electron correlation effects; a standard linear differential equation was derived to define the function. The equation depends on the functions of independent particles; a generalization of the Hartree-Fock equations including electron correlation was obtained for these functions. The total energy calculation of two-electron ions shows that even solving an ordinary differential equation for the function of independent particles represented by the functions of noninteracting electrons leads to higher accuracy than the one achieved in the Hartree-Fock theory.     

Correlation method for comparison of selectivity and retention on different chiral stationary phases

Summary The main chromatographic properties: selectivity and retention of two chiral stationary phases: (R)-3,5-dinitrobenzoylphenylglycine (CSP I) and (S)-3,5-dinitro-benzoylleucine (CSP II) have been compared on the basis of correlation of retention factors of derivatized esters of amino acids and derivatized aminoalcohols. The differences in retention and selectivity for the two CSPs can be easily estimated from the correlation equation. It is shown that in the case of the correlation for two sets of retention factors obtained on two different CSPs, it is mainly the intercept that decides which CSP has the better selectivity. It is demonstrated that the correlation method provides more informations on the selectivity and retention than comparison of the chromatographic data of single pairs of enantiomers. Additionally, the possible influence of the polar modifier mixed with n-hexane as diluent on the constants in the correlation equation is demonstrated.     

[Bmim]FeCl_4离子液体的物理性质

研究了自制[Bmim]FeCl4离子液体的电导率、黏度与温度的关系,并与文献数据进行了对比.结果表明,采用落球法和旋转法都能准确地测量[Bmim]FeCl4离子液体的黏度;与Andrade方程相比,VTF方程能更好地拟合[Bmim]FeCl4离子液体的黏度和温度的关系,其相关系数达0.999 9.采用不同电导率仪测量的[Bmim]FeCl4离子液体的电导率有较大差别;相比Arrhenius方程而言,VTF方程能更好地拟合电导率与温度的关系;随着温度的变化,电导率与黏度的关系符合Walden规则,其相关系数达到0.99以上.     

Calculating Density of Molecular Liquids Using Agrawal-Thodos Equation

The correlation between the parameters of the Agrawal-Thodos equation, the fundamentalconstants of a substance are established. A modified equation is proposed, in which the minimum set of easily measurable properties of the substance is used as input data.