Coefficient Of Polymer Solutions Research Articles

Nanoparticle diffusion in polymer melts in the presence of weak nanoparticle-monomer attractive interactions: A mode-coupling theory study.

Mode-coupling theory is developed and employed to compute the nanoparticle diffusion coefficient in polymer solutions. Theoretical results are compared with molecular dynamics simulation data for a similar model. The theory properly reproduces the simulated effects of the nanoparticle size, mass, and concentration on the nanoparticle diffusion coefficient. Within the mode-coupling theory framework, a microscopic interpretation of the nonmonotonic dependence of the diffusion coefficient on the nanoparticle concentration is given in terms of structural and dynamic effects. Both the size dependence and mass dependence of the diffusion coefficient indicate a pronounced breakdown of the Stokes-Einstein relation for the present model.

Investigation into mobility control mechanisms by polymer flooding in offshore high-permeable heavy oil reservoir

ABSTRACT The systematic understanding of the mobility control of polymer solution in porous media is conducive to the engineering application and development of polymer flooding technology. In this paper, two kinds of polymers (partially hydrolyzed polyacrylamide (HPAM) and MJ-10 (a hydrophobically associating polyacrylamide, HAPAM)) with different adsorption characteristics were used to build a solution system with different performance characteristics. And run a series of viscosity measurement, residual resistance factor (RRF) measurement and oil displacement experiments on man-made sand packs. The results show that the viscosity and residual resistance coefficient of polymer solution can enhance its fluidity control. The higher the viscosity of solution, the higher the RRF, and the higher the displacement efficiency. The solution system HM3 can make full use of the solution characteristics of the two polymers to obtain a moderate solution viscosity and residual resistance coefficient. Compared with a single solution H2 and M2, it can increase the oil recovery by 5% in the low permeability layer. The compound application of polymer solution will be a development direction of polymer flooding in the future.

Thermal diffusion in polymer solutions: Approaching spinodal

This paper aims to theoretically explain the behavior of thermal diffusion coefficient in polymer solutions; specifically, in the vicinity of the unstable regions of phase diagrams. Based on an equation that was derived in the framework of classical irreversible thermodynamics, a dimensionless number was introduced that plays a crucial role in determining the thermal diffusion in polymer solutions. The behavior of thermal diffusion coefficient in various phase diagrams was investigated by changing the Flory-Huggins interaction parameter to include concentration and temperature dependencies using Koningsveld interaction factor. It was shown that irrespective of the types of phase diagrams, the proposed equation for thermal diffusion becomes zero at infinite dilution and takes finite values on the spinodal line. Moreover, it was illustrated that in a binary polymer solution the Soret coefficient (the ratio of the thermal diffusion coefficient to the mutual diffusion coefficient) diverges at the critical point, and more importantly it was predicted that the divergent behavior of the Soret coefficient is observed at all the points of the spinodal line.

Mutual diffusion in polymer solutions: Spanning phase diagrams

Abstract This paper aims to discuss the trend of variation of mutual diffusion coefficient in polymer solutions exhibiting different phase behavior. An equation for mutual diffusion coefficient in polymer solutions was derived in the framework of classical irreversible thermodynamics using Onsager’s variational principle. The behavior of mutual diffusion coefficient in different phase diagrams was investigated by changing the Flory-Huggins interaction parameter to include concentration and temperature dependencies using Koningsveld interaction factor. The proposed diffusion coefficient satisfies the asymptotic behavior at infinite dilution, becomes zero on the spinodal line and changes sign at the onset of entering the unstable zone of phase diagrams. It was shown that the diffusion slows down near the critical point and in general by approaching the spinodal curve. Moreover, it was shown that the derived equation for mutual diffusion coefficient can be expressed in terms of osmotic bulk modulus which is consistent with the result of a variational approach using Landau-Ginsberg-Wilson Hamiltonian.

Prediction of infinite dilution solvent activity coefficient in rubbery polymer solutions using Engaged Species Induced Clustering (ENSIC) model

AbstractIt is extremely important to predict infinite dilution solvent activity coefficients in rubbery polymers in design and operation of polymer‐related processes. Many models have been developed to predict the activity coefficients. However, the accuracies of these models are not satisfactory. This article advances a method for predicting the infinite solvent dilution activity coefficients in the rubbery polymers, using the Engaged Species Induced Clustering (ENSIC) model. It elucidates the physiochemical significance and mathematical meaning of the parameters in the ENSIC model. In this article, the ENSIC approach has been proven to agree extremely well with the experimental data in both correlating the finite dilution solvent activity coefficient and predicting the infinite dilution solvent activity coefficient for rubbery polymer/solvent systems. In other words, both the ENSIC equation and its derivative at extremely low solvent concentration are in good agreement with the experimental data. In addition, the article indicates that the ENSIC model is much more accurate than another kind of empirical models‐ the F–H and related models in predicting the infinite dilution solvent activity coefficients in polymer solutions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1668–1675, 2006

The Second Osmotic Virial Coefficient of Polymer Solutions

The second osmotic virial coefficient, A2, of chain molecules confined to SC, FCC, and diamond lattices was determined by Monte Carlo methods. In each case the dependence of A2 on the chain length follows a power law with nearly identical exponents, which are in accordance with the scaling predictions. A fair agreement with the results of other authors for models in the continuous space indicates a universal behavior.

The second osmotic virial coefficient of athermal polymer solutions

The present paper attempts to evaluate the second virial coefficient of a polymer solution and to assess its dependence on chain length. A lattice model is used, and the `lattice constants' cnm of two separated chains of lengths n and m are calculated for values from 2 to 12 for a number of two- and three-dimensional lattices. The use of two parameters m, n allows polydispersity to be taken into account. For a polydisperse solution the second virial coefficient is determined by bnm = -cnm/cncm, where cn is the lattice constant of a single chain of length n. The bnm are fitted to an asymptotic formula A(nm)γ, and it is suggested that γ = 7/8 in three dimensions and 3/4 in two dimensions. Some experimental tests are suggested.

The effect of concentration on diffusion coefficient in polymer solutions

AbstractA microinterferometric method was used to measure the diffusion coefficient as a function of concentration in the system dimethylformamide‐polyacrylonitrile at 25°C. The diffusion coefficient increases with increasing polymer concentration up to the maximum employed, 17.72% by weight. The theoretical basis for this type of behavior is explained. The diffusion coefficient in the limit as the polymer concentration approaches zero was calculated from theory to be 0.30 × 10−6 sq.cm./sec. This value is consistent with the diffusion coefficients obtained experimentally.

高分子溶液の第2ビリアル係数についての研究

分別ポリジメチルシロキサン (分子量107, 000) を種々の溶媒に溶かし, 広い温度にわたって浸透圧と粘度を測定して, 各溶液の第2ビリアル係数と固有粘度を求めた。得られた結果を要約すると次のようになる。1) 第2ビリアル係数の大きさおよび温度係数は固有粘度のそれらに関係づけられる。2) 希釈エントロピーには溶媒分子の幾何学的性質が影響する。3) 希釈熱は高分子鎖と溶媒分子の置換基によっても影響される。4) ポリジメチルシロキサンのθ-溶媒中における広がりの尺度としてをると1.56である。

Statistical Thermodynamics of Polymer Solutions. II. Excluded Volume Effect and Second Virial Coefficient

A recently published theory of the second virial coefficient in polymer solutions is modified to take account of the fact that in a good solvent the mean dimensions of two interacting linear molecules are increased beyond random-flight size through both intermolecular and intramolecular mutual volume exclusion among chain segments. Since the model for a bimolecular cluster bears a formal resemblance to a cruciform branched chain, a method for calculating the dimensions of such polymers can be applied to the two-molecule problem. This treatment improves the agreement of calculated virial coefficients with experiment as compared with the simpler assumption, made in the original formulation of the theory, that each molecule of an interacting pair is expanded independently in consequence of intramolecular interactions alone.

The Third Virial Coefficient in Polymer Solutions

The Third Virial Coefficient in Polymer Solutions

The Third Virial Coefficient in Polymer Solutions

With the aid of approximate models for the intermolecular potential energy, the third virial coefficient Γ3 in the virial expansion for the osmotic pressure of a dilute polymer solution has been determined as a function of the second coefficient and one additional parameter obtainable from intrinsic viscosity or light scattering measurements. The theory and experimental results agree in indicating that the ratio Γ3/Γ22 for most solutions is markedly less than the value of ⅝ given by the hard sphere molecular model proposed by others for the estimation of Γ3. The limitations are discussed under which light scattering may be used for evaluation of the virial coefficients.