| 1. |
- Forsman, Jan, et al.
(author)
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Density functional studies of solvation forces in hard sphere polymer solutions confined between adsorbing walls. I. Solvent effects and dependence on surface potential range.
- 2003
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606. ; 118:16, s. 7672-7681
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Journal article (peer-reviewed)abstract
- Solvation forces between large surfaces in athermal polymer solutions, in which both solvent particles and polymers are adsorbed at the surfaces, are studied with density functional theory. We investigate how the range of the surface potential affects the net interaction between the surfaces. Predictions from treatments in which the solvent is explicitly induced are compared with those obtained with more approximate models, where the solvent is either neglected, or enters the description implicitly. The results are interpreted via comparisons with simpler model systems. It is shown that a long-ranged surface potential, acting equally on monomers and solvent, leads to a solvent dominated repulsive solvation force, while polymer specific contributions dominate the net interactions when the adsorption potential has a short range. Effects of preferential polymer adsorption are also investigated. ©2003 American Institute of Physics.
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| 2. |
- Forsman, Jan, et al.
(author)
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An improved density functional description of hard sphere polymer fluids at low density.
- 2003
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 119:4, s. 1889-1892
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Journal article (peer-reviewed)abstract
- A refined formulation of an existing polymer density functional theory is presented, wherein an intrachain stiffness is introduced via a bending potential. Comparisons with Metropolis Monte Carlo simulations in a slit geometry shows that this leads to a considerable improvement of the predicted density profile for a hard sphere polymer melt, at low density. We also show how the corresponding surface interactions are affected by the inclusion of this intramolecular correlation. We expect that the improvement obtained will be even more important in the description of, for example, polyelectrolytes, although such comparisons are not made in this preliminary study. ©2003 American Institute of Physics.
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| 3. |
- Forsman, Jan, et al.
(author)
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Density Functional Study of Surface Forces in Athermal Polymer Solutions with Addititve Hard Sphere Interactions. Solvent Effects, Capillary Condensation and Capillary-Induced Surface Transitions.
- 2002
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 117:4, s. 1915-1926
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Journal article (peer-reviewed)abstract
- A density functional theory for polymer solutions is generalized to cases where the monomers have a different diameter to the solvent. An appropriate free energy functional is obtained by integration of the generalized Flory equation of state for such systems. This functional predicts that entropic demixing may occur in polymer solutions in which the solvent particles are smaller than the monomers. Demixing is promoted not only by a large size disparity, but also by a high pressure as well as by polymer length. The existence of two separate phases in the bulk solution suggests the possibility of capillary-induced phase transitions, even when the confining surfaces are hard, but otherwise inert. We examine such phase transitions and their relation to surface forces and colloidal stability. The density functional theory also predicts that under certain conditions, layering transitions will occur at hard and flat surfaces. A transition from a thin to a thick polymer-rich surface layer may take place as the separation between two surfaces is decreased, and we study the concomitant change on the surface force. Stable thick phases are predicted even at very large undersaturations, and they give rise to a profound increase of the range and strength of the surface force.We furthermore include comparisons with predictions from a model in which the solvent only enters the description implicitly. Responses of the surface forces to changes in monomer diameter, solvent diameter, polymer density, and chain length are investigated.
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| 4. |
- Forsman, Jan, et al.
(author)
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Evaluating the accuracy of a density functional theory of polymer solutions with additive hard sphere diameters
- 2004
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 120:1, s. 506-510
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Journal article (peer-reviewed)abstract
- We assess the accuracy of a density functional theory for athermal polymer solutions, consisting of solvent particles with a smaller radius than that of the monomers. The monomer and solvent density profiles in a slit bound by hard, flat, and inert surfaces are compared with those obtained by a Metropolis Monte Carlo simulation. At the relatively high density at which the comparison is performed, there are considerable packing effects at the walls. The density functional theory introduces a simple weight function to describe nonlocal correlations in the fluid. A recent study of surface forces in polymer solutions used a different weighting scheme to that proposed in this article, leading to less accurate results. The implications of the conclusions of that study are discussed. (C) 2004 American Institute of Physics.
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| 5. |
- Woodward, C E, et al.
(author)
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Density functional study of surface forces in solutions containing star-shaped polymers
- 2004
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In: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 37:18, s. 7034-7041
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Journal article (peer-reviewed)abstract
- Density functional theory is used to study polymer solutions between surfaces in equilibrium with a bulk solution. We investigate the effect on the surface interaction free energy of having star polymers with different numbers of arms. In addition, we consider the role played by the strength of the adsorption potential and the concentration of the polymer molecules. The interaction free energy is found to scale quite well with the number of arms on the stars, and the separation dependence of the interaction scales approximately with the radius of gyration. When the adsorption potential is weak, the polymer molecules are depleted. A free energy barrier is nevertheless present-a phenomenon often referred to as depletion stabilization. The barrier scales with the number of arms on the star polymers.
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