Pressure dependence of the second virial coefficient of dilute polystyrene solutions

The pressure derivatives of the second virial coefficients [dA₂/dP; 0.1 ≤ P (MPa) ≤ 35.0] for dilute polystyrene (PS) solutions in good, θ, and poor solvents were measured with static light scattering. The solvent quality improved (dA₂/dP > 0) in the good and poor solvents that we investigated (toluene, chloroform; and methylcyclohexane) but deteriorated (dA₂/dP < 0) in θ solvents (cyclohexane and 50‐50 cis,trans‐decalin). The effects of temperature [22 < T (°C) < 45] and molecular weight [25 × 10³ < weight‐average molecular weight (amu mol^?1) < 900 × 10³] on dA₂/dP for PS/cyclohexane solutions were examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3070–3076, 2003     

The structuredness of solvents. 2. Data for ambient conditions

In view of the inadequacy of Trouton's constant for the expression of the structuredness of solvents at ambient temperatures, alternative measures have been sought. Calculations of the entropy deficit _vapS⁰/R of solvents at ambient conditions relative to their vapors and compared to presumably unstructured alkanes with the same number and arrangement of skeletal atoms have been made. Data for nonpolar, dipolar aprotic, non-hydroxylic protic and hydroxylic solvents are presented, with _vapS⁰/R>2 representing structured solvents. Empirically, the heat capacity density of solvents at ambient temperatures, [C _p (l)-C _p (g)]/V], is another meaningful measure of the structuredness of solvents, compatible with the former one. Values>0.6 J-K^–1-cm^–3 signify a structured solvent.     

渗透压法对牛血清蛋白在NaCl水溶液中相互作用的研究

测量了牛血清蛋白不同pH值和不同离子强度Nacl水溶液中的渗透压,计算了渗透第二维里系数,按照Prausnitz提出的分子热学模型计算了蛋白质之间的静电排斥能、色散吸引能和离子排斥体积产生的吸引势能,并对这三种势能与溶液pH值和离子强度的变化关系进行讨论。     

Classical and quantal calculations of the dimerization constant and second virial coefficient for argon

Summary Computations of the second virial coefficient and thermodynamic equilibrium constant for the dimerization of argon are reported. These are based on accurate analytic representations of the Ar-Ar interaction energy. Calculations have been made using classical and quantal statistical mechanics and for the second virial coefficient the JWKB series as well.     

Electrical conductance of aqueous solutions of KCl solutions at pressures up to 2000 atm

Electrical conductance measurements are reported for aqueous KCl solutions at 25°C as a function of concentration up to 0.02 M and pressure up to 2000 atm. The data from 103 runs were analyzed with the Fuoss-Hsia-Fernandez-Prini (FHFP) equation. The standard error of fit varies from 0.018 at 1 atm to 0.12 at 2000 atm. The increase of with pressure arises from increasing nonrandomness in the distribution of errors about the FHFP equation, suggesting that modifications in the theory are necessary. Departures from the Walden product for KCl as a function of pressure are compared with MgSO₄ and CaSO₄ in aqueous solutions.     

Mutual macromolecular crowding as the basis for polymer solution non‐ideality

Semidilute polymer solutions differ greatly from dilute solutions in properties such as viscosity, relaxation time, elastic modulus, colloid osmotic pressure, and light scattering. Previously, Matsuoka and Cowman proposed a single semiempirical expression for the nonideality contribution due to the concentration and intrinsic viscosity dependence, which has no other adjustable parameters, but quantitatively fits data for flexible, semiflexible, and rigid polymers in good solvents. In this report, the excluded volume theory as proposed by Ogston and Laurent is generalized to include mutual crowding between identical polymers based on hydrodynamic volumes, and applied to derive the expression for the nonideality contribution to specific viscosity, colloid osmotic pressure, and light scattering. Additionally, consideration of the contribution of mutual macromolecular crowding to the effective solvent viscosity allows prediction of polymer relaxation time and elastic modulus in semidilute solutions. This theoretical approach now allows the prediction of semidilute polymer solution properties based only on concentration and intrinsic viscosity, and conversely allows intrinsic viscosity (and thus average molecular weight) to be calculated from measurements made on semidilute solutions of known concentration. Copyright © 2016 John Wiley & Sons, Ltd.     

Vapor pressure studies of hydrophobic association. Thermodynamics of fluorobenzene in dilute aqueous solution

An automated vapor pressure apparatus has been used to obtain measurements of the vapor pressure of aqueous solutions of fluorobenzene at temperatures of 15, 25, 35, and 45°C, and in the concentration range 0 to 0.011M. The results have been interpreted to infer the dimerization constant of fluorobenzene in very dilute aqueous solutions, equivalent to the second virial coefficient of interaction between fluorobenzene molecules. The hydrophobic association of fluorobenzene molecules is thermodynamically quite similar to that of benzene at comparable temperatures and concentrations. A dimerization constant of fluorobenzene of 0.56 M^–1 at 30°C and an endothermic enthalpy of association equal to 3.9 kcal-mol^–1 are calculated from the measurements.     

A light-scattering photometer for use at elevated pressures

A new light scattering photometer has been designed in order to perform light-scattering measurements at various temperatures and under pressures of 1–1000 atm. Since the scattering angle is constant (90°C), the dimensions of the dissolved molecules are determined by measuring the intensity at different wavelengths. The method of measurement, the calibration of the instrument, and the treatment of data are described. By a series of test measurements on polystyrene in trans-decalin solutions it is shown that one obtains reliable results and finds considerable effects of pressure on the radius of gyration and the fundamental thermodynamic properties of the system.     

On the thermodynamics of the McMillan–Mayer state function

The osmotic second virial coefficient is a key parameter in light scattering, protein crystallisation, self-interaction chromatography, and osmometry. The interpretation of the osmotic second virial coefficient depends on the solution theory. On the macroscopic level an expansion of the osmotic pressure is employed. A common statistical interpretation of the osmotic second virial coefficient of the expansion employs the McMillan–Mayer framework and the potential of mean force to characterise the solute–solute interaction. Supplementary to the statistical interpretation, it may be advantageous to develop the McMillan–Mayer framework in a classical thermodynamic context for which we develop the relationship between the state function of the McMillan–Mayer framework and the Helmholtz state function.     

Crystallization of polypropylene,nylon-66 and poly(ethylene terephthalate) at pressures to 200 MPa: Kinetics and characterization of products

The crystallization kinetics of polypropylene (PP), polyamide (PA66), and poly(ethylene terephthalate) (PET) were studied, using a pressure dilatometer (to 200 MPa) to follow the volume changes associated with the crystallization process. The commonly used Avrami equation fitted the isothermal/isobaric crystallization data of PP and PA66 well. The Avrami exponent n was between 1.3 and 1.7, independent of crystallization pressure and temperature. Lines of constant Avrami rate parameter Z in the P-T plane were essentially parallel to the pressure dependence of the melting points and crystallization temperatures. However, the Avrami equation was not suitable for PET. The Malkin, Dietz, and Kim equations provided better fits. The crystallization half-time of PET increased with pressure at constant supercooling, in contrast to PP and PA66, for which it remained essentially unchanged. X-ray diffraction, differential scanning calorimetry, and pressure dilatometry were used to study the effect of formation pressure on the crystal structure, the melting point, and the density of products which were crystallized for short times (minutes) at various temperatures and pressures. No new crystal structures were found for PA66 and PET, but a mixture of monoclinic and triclinic crystals existed in PP above a formation pressure of 50 MPa. The melting points increased with formation pressure for PET, but remained unchanged for PP and PA66. Density at ambient conditions decreased with formation pressure for PP, but increased for PET and PA66. © 1994 John Wiley & Sons, Inc.     

动态膜渗透压法测定生漆多糖水溶液

<正> 生漆是一种性能优异的超耐久涂料,其主要成份为漆酚、漆酶、糖蛋白、多糖和水。多糖由D-半乳糖(65％),4-O-甲基-D-葡萄糖醛酸(24％),D-葡萄糖醛酸(3％),L-阿拉伯糖(4％)和鼠李糖(3％)组成。它带大量支链,在侧链上有大约1/4mol羧基从而显示聚电解质溶液性质。     

Liquid-vapor equilibrium of dilute aqueous solutions of methanol

Numerous sets of vapor pressure-composition data for methanol in dilute aqueous solutions at 25°C and 35°C have been obtained with an automated vapor pressure apparatus developed in this laboratory. Activity coefficients of both components and values of the pairwise free energy of interaction of methanol molecules have been inferred from the results. The osmotic second virial coefficient of methanol has also been calculated and compared with literature values of this quantity.     

Estimation of third virial coefficients at low reduced temperatures

We use the Clausius–Clapeyron equation to calculate third virial coefficients at low reduced temperatures. This procedure gives an alternative to predict third virial coefficients in a region where the third virial coefficient is difficult to measure. We compare the results of this method with published third virial coefficient data. Calculated third virial coefficients have average percentage deviations within 5% of the experimental values at reduced temperatures between 0.8 and 1.0.     

Adsorption deformation of zeolite NaX at high pressures of xenon

The deformation of pellets of crystalline zeofite NaX upon adsorption of Xe at pressures from 0.001 to 7 MPa and temperatures from 252.5 to 333 K was studied. In the temperature range studied, the relative linear deformation of zeolite crystals is negative in the initial adsorption region. When the adsorption of Xe increases, its value passes through a minimum and then increases sharply taking positive values at high adsorption volume filling of micropores.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 336–338. February, 1996     

Disordered pyrochlore CsMgInF6 at high pressures

High pressure behaviour of disordered pyrochlore CsMgInF₆ (Pnma, Z=4) has been studied with powder and single-crystal X-ray diffraction to 8.0 and 6.94 GPa, respectively, in diamond anvil cells at room temperature. The material is structurally stable to at least 8.0 GPa with no ordering of the In³⁺ and Mg²⁺ cations. The P-V data are fitted by a Birch-Murnaghan equation of state with the zero-pressure bulk modulus B₀=33.4(3) GPa and the unit-cell volume at ambient pressure V₀=603.2(4) Å³ for the first pressure derivative of the bulk modulus B′=4.00. The major contribution to the bulk compressibility arises from the changes in the coordination sphere around the Cs atoms. The effect of hydrostatic pressure on the crystal structure of CsMgInF₆ is comparable to the effect of chemical pressure induced by the incorporation of ions of different sizes into the A and B sites in defect AB²⁺B′³⁺F₆ pyrochlores.     

Solution properties,unperturbed dimensions,and chain flexibility of poly(1‐adamantyl acrylate)

Poly(1‐adamantyl acrylate) (PAdA) exhibits much higher glass transition and degradation temperatures than other polyacrylates. However, the quantitative evaluation of the stiffness of this polymer chain has not been reported previously. In this study, the dilute solution properties and conformational characteristics of PAdA were evaluated using viscometry and scattering techniques. The unperturbed dimensions of this polymer were evaluated using the Burchard–Stockmayer–Fixman extrapolation and the touched‐bead wormlike chain model. The PAdA chain has a comparable persistence length, diameter per bead and characteristic ratio to poly(methyl methacrylate) and polystyrene. All these results indicate that PAdA is less flexible than common polyacrylates. In addition, the second virial coefficients (A₂) of PAdA in different solvents obtained by static light scattering were compared. Among the solvents investigated, tetrahydrofuran is a moderate solvent. Radius of gyration of a polymer sample in the various solvents ranged from 16.8 to 30.3 nm. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1526–1531     

Phase stability of some actinides with brannerite structure at high pressures

Structure behavior of actinide brannerites ThTi₂O₆, Y_0.5U_0.5Ti_1.5Nb_0.5O₆ and their analog oxide CeTi₂O₆ was studied at high pressure by using in situ x-ray diffraction, Raman scattering and infra-red absorption techniques, respectively. Brannerite structure was found to be not stable and started to become amorphous at pressures above 20 GPa. Some minor crystalline phase(s) due to phase decomposition was observed in all the three samples during pressurization. In addition, the observed bulk modulus indicated that the actinide-bearing brannerites are more compressible than their analog compound CeTi₂O₆, which may be related to the asymmetric 5f electron orbits of actinide elements.     

The viscosity of triethylamine vapor at low densities and in the saturated vapor phase

For the first time, results of high-precision measurements of the viscosity coefficient of triethylamine vapor at low densities are reported. The relative measurements with an all-quartz oscillating-disk viscometer were carried out along seven isochores at densities from 0.002 to 0.009 mol m⁻³ in the temperature range between 298 and 498 K. The uncertainty is estimated to be ±$\pm$0.2% at ambient temperature, increasing up to ±$\pm$0.3% at higher temperatures. First isothermal values were recalculated from the original experimental data and then evaluated with a first-order expansion for the viscosity, in terms of density. In addition, viscosity values of the saturated vapor were determined at low temperatures. The results are utilized to model the viscosity coefficient of triethylamine vapor at moderately low densities. A so-called individual correlation on the basis of the extended theorem of corresponding states was employed to describe the zero-density viscosity coefficient, whereas the Rainwater–Friend theory was used to represent the initial density dependence expressed as second viscosity virial coefficient.