Comparison of random-walk density functional theory to simulation for bead-spring homopolymer melts

Frischknecht, Amalie L.; Curro, John G.

doi:10.1063/1.1768517

Cited by 12 publications

(12 citation statements)

References 44 publications

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“…As seen in earlier work on polyethylene 11 and beadspring 34 polymers, the DFT/PRISM approach gives good qualitative and sometimes quantitative agreement with simulation. To make the theory more useful for quantitative predictions, it is necessary to compensate for the combined effects of approximations in the bulk direct correlation functions from PRISM theory and the approximate form of the mean field in eq 11.…”

Section: Density Functional Theorysupporting

confidence: 66%

“…To make the theory more useful for quantitative predictions, it is necessary to compensate for the combined effects of approximations in the bulk direct correlation functions from PRISM theory and the approximate form of the mean field in eq 11. Toward this end we follow the approach used by Frischknecht and Curro 34 and in our previous study 11 and include an adjustable multiplicative factor in the PRISM direct correlation functions used as input to DFT.…”

Section: Density Functional Theorymentioning

confidence: 99%

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Density Functional Theory and Molecular Dynamics Simulation of Poly(dimethylsiloxane) Melts near Silica Surfaces

Nath¹,

Frischknecht²,

Curro³

et al. 2005

Macromolecules

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Classical density functional theory (DFT) is applied to study properties of fully detailed, realistic models of poly(dimethylsiloxane) liquids near silica surfaces and compared to results from molecular dynamics simulations. In solving the DFT equations, the direct correlation functions are obtained from the polymer reference interaction site model (PRISM) theory for the repulsive parts of the interatomic interactions, and the attractions are treated via the random-phase approximation (RPA). Good agreement between density profiles calculated from DFT and from the simulations is obtained with empirical scaling of the direct correlation functions. Separate scaling factors are required for the PRISM and RPA parts of the direct correlation functions. Theoretical predictions of stress profiles, normal pressure, and surface tensions are also in reasonable agreement with simulation results.

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Section: Density Functional Theorysupporting

confidence: 66%

Section: Density Functional Theorymentioning

confidence: 99%

Density Functional Theory and Molecular Dynamics Simulation of Poly(dimethylsiloxane) Melts near Silica Surfaces

Nath¹,

Frischknecht²,

Curro³

et al. 2005

Macromolecules

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“…These features of the density profiles are typical of liquids close to smooth walls 23 and are found in many other studies. [24][25][26][27][28] Upon cooling the solvent concentration in the film increases. This has two consequences.…”

Section: Resultsmentioning

confidence: 99%

Molecular dynamics simulations of concentrated polymer solutions in thin film geometry. I. Equilibrium properties near the glass transition

Peter

Meyer

Baschnagel

2009

The Journal of Chemical Physics

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We report on results of molecular dynamics simulations for supported polymer films with explicit solvent. The simulation represents the polymers by bead-spring chains and the solvent particles by monomers. The interaction between polymer and solvent favors mixing. We find that the solvent acts as a plasticizer. The glass transition temperature T(g) is reduced relative to the pure polymer film. Near T(g) we explore equilibrium properties as a function of temperature and solvent concentration. We find that the structure and dynamics of the films are spatially heterogeneous. The solvent density is enriched at the supporting wall and at the free surface where the film is in equilibrium with solvent vapor. At both interfaces the solvent dynamics is fast, but smoothly crosses over to bulk dynamics when moving from the interfaces toward the center of the film. A smooth gradient from enhanced dynamics at the interfaces to bulk behavior in the film center is also found for the monomers. We show that the same formula used to parametrize the spatial gradient of the dynamics in the pure polymer film may also be applied here. Furthermore, we determine the concentration dependence of the relaxation time of the solvent in the center of film and compare this dependence to models proposed in literature.

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“…In addition, the details of the molecular model can influence the way in which adsorbed chains emanate from the substrate, affecting the large length scale structure of the adsorbed layer (formation of loops and tails). Looking from another perspective, it can be said that, through its representation of internal chain rigidity, the wormlike chain, when compared to the Gaussian one, 12 incorporates an additional length scale on the level of the chain persistence length; this can enhance its predictive capabilities with respect to some properties. For very long chains, the large length-scale properties of both the Gaussian and wormlike models are expected to converge to the "exact" properties, as extracted, for example, by atomistic simulation.…”

Section: Introductionmentioning

confidence: 99%

Self-Consistent-Field Study of Compressible Semiflexible Melts Adsorbed on a Solid Substrate and Comparison with Atomistic Simulations

et al. 2005

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The present work addresses the problem of a self-consistent-field (SCF) description of a specified polymer melt/solid substrate interfacial system. Key points of the employed method are the coarse-grained representation and the numerical treatment of the continuous-space SCF theory. Compared to other works on polymer adsorption, the main difference of the current approach is the description of the polymer coil connectivity through the wormlike chain model, which, after incorporating local stiffness, reproduces two characteristic lengths of the studied polymer: the mean-squared end-to-end distance and the contour length. As a test case, polyethylene melts adsorbed on a graphite substrate are considered; recent atomistic simulations of the same systems are used to evaluate the theoretical approach. For comparison and elucidation of some effects of chain stiffness on conformational properties of adsorbed molecules, an alternative (and more common) representation of chain connectivity through the Gaussian model, reproducing the mean-squared end-to-end distance, is also considered. Results refer to local and global chain conformational properties, with an emphasis on the latter. In particular, predictions for the shape of chains are obtained, while the conformations of adsorbed molecules are quantified in terms of tails, loops, and trains. For small chain lengths, both the Gaussian and the wormlike chain models deviate considerably from the simulation data. At intermediate chain lengths, however (such as C400), the predictive power of the wormlike model is very good for several conformational properties. On the contrary, predictions from the Gaussian model, especially for the case of loops, deviate considerably from simulations over a broader range of molecular lengths.

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Comparison of random-walk density functional theory to simulation for bead-spring homopolymer melts

Cited by 12 publications

References 44 publications

Density Functional Theory and Molecular Dynamics Simulation of Poly(dimethylsiloxane) Melts near Silica Surfaces

Density Functional Theory and Molecular Dynamics Simulation of Poly(dimethylsiloxane) Melts near Silica Surfaces

Molecular dynamics simulations of concentrated polymer solutions in thin film geometry. I. Equilibrium properties near the glass transition

Self-Consistent-Field Study of Compressible Semiflexible Melts Adsorbed on a Solid Substrate and Comparison with Atomistic Simulations

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