Self-consistent integral equation theory for polyolefins: Comparison to molecular dynamics simulations and x-ray scattering

Pütz, Mathias; Curro, John G.; Grest, Gary S.

doi:10.1063/1.1338505

Cited by 69 publications

(80 citation statements)

References 37 publications

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“…First, the direct and total distribution functions in real space are calculated from numerical Fourier transform of Equation 22 and Equation 23. Then, the interaction potential is calculated numerically evaluating the HNC potential, as above,…”

Section: Block Averaged Potentialmentioning

confidence: 99%

“…In the united representation, each CH x group is represented as a single interaction site. [23] This model has been used extensively to represent hydrocarbons of different chemical specificity. The UA simulations use the TRAPPE forcefield parameters, [24] and are performed using the LAMMPS molecular dynamics code [27].…”

Section: B Mesoscale Molecular Dynamics Simulationsmentioning

confidence: 99%

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An analytical coarse-graining method which preserves the free energy, structural correlations, and thermodynamic state of polymer melts from the atomistic to the mesoscale

McCarty

Clark

Copperman

et al. 2014

The Journal of Chemical Physics

111

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Structural and thermodynamic consistency of coarse-graining models across multiple length scales is essential for the predictive role of multi-scale modeling and molecular dynamic simulations that use mesoscale descriptions. Our approach is a coarse-grained model based on integral equation theory, which can represent polymer chains at variable levels of chemical details. The model is analytical and depends on molecular and thermodynamic parameters of the system under study, as well as on the direct correlation function in the k → 0 limit, c0. A numerical solution to the PRISM integral equations is used to determine c0, by adjusting the value of the effective hard sphere diameter, dHS, to agree with the predicted equation of state. This single quantity parameterizes the coarse-grained potential, which is used to perform mesoscale simulations that are directly compared with atomistic-level simulations of the same system. We test our coarse-graining formalism by comparing structural correlations, isothermal compressibility, equation of state, Helmholtz and Gibbs free energies, and potential energy and entropy using both united atom and coarse-grained descriptions. We find quantitative agreement between the analytical formalism for the thermodynamic properties, and the results of Molecular Dynamics simulations, independent of the chosen level of representation. In the mesoscale description, the potential energy of the soft-particle interaction becomes a free energy in the coarse-grained coordinates which preserves the excess free energy from an ideal gas across all levels of description. The structural consistency between the united-atom and mesoscale descriptions means the relative entropy between descriptions has been minimized without any variational optimization parameters. The approach is general and applicable to any polymeric system in different thermodynamic conditions.

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Section: Block Averaged Potentialmentioning

confidence: 99%

Section: B Mesoscale Molecular Dynamics Simulationsmentioning

confidence: 99%

An analytical coarse-graining method which preserves the free energy, structural correlations, and thermodynamic state of polymer melts from the atomistic to the mesoscale

McCarty

Clark

Copperman

et al. 2014

The Journal of Chemical Physics

111

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“…The theory makes use of the generalized Ornstein-Zernike equation [27][28][29] of Chandler and Andersen.…”

Section: Prism Theorymentioning

confidence: 99%

Structure of Poly(dialkylsiloxane) Melts: Comparisons of Wide-Angle X-ray Scattering, Molecular Dynamics Simulations, and Integral Equation Theory

et al. 2007

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Wide-angle X-ray scattering, molecular dynamics (MD) simulations, and integral equation theory are used to study the structure of poly(diethylsiloxane) (PDES), poly(ethylmethylsiloxane) (PEMS), and poly-(dimethylsiloxane) (PDMS) melts. The structure functions of PDES, PEMS, and PDMS are similar, but systematic trends in the intermolecular packing are observed. The local intramolecular structure is extracted from the experimental structure functions. The bond distances and bond angles obtained, including the large Si-O-Si angle, are in good agreement with the explicit atom (EA) and united atom (UA) potentials used in the simulations and theory and from other sources. Very good agreement is found between the MD simulations using the EA potentials and the experimental scattering results. Good agreement is also found between the polymer reference interaction site model (PRISM theory) and the UA MD simulations. The intermolecular structure is examined experimentally using an appropriately weighted radial distribution function and with theory and simulation using intermolecular site/site pair correlation functions. Experiment, simulation, and theory show systematic increases in the chain/chain packing distances in the siloxanes as the number of sites in the pendant side chains is increased.

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“…It should be mentioned that it is not necessary to perform a new Monte Carlo simulation with each iteration. Reweighting techniques 25 can be used to greatly reduce the number of simulations that need to be carried out during the course of the self-consistent calculation. The final output of PRISM theory gives a self-consistent solution of the intra, Ω pp (k), and intermolecular, g Rγ (r), structure.…”

Section: Theory and Computationmentioning

confidence: 99%

Integral Equation Theory of Polymer Solutions: Application to Polyethylene/Benzene Solutions

Mendez

Curro

2004

Macromolecules

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Solutions of polyethylene macromolecules immersed in benzene were modeled with selfconsistent polymer reference interaction site model (PRISM) theory. The PRISM integral equations for the solution were solved self-consistently for the polyethylene intramolecular chain structure and intermolecular polymer and solvent correlations at various mole fractions. We found that explicitly considering the solvent molecules leads to considerably more short-range structure in the radial distribution function of the polymer, relative to the polymer without solvent at the same concentration. The long-range intermolecular correlations between polymer sites in the correlation hole regime decreased inversely with the polymer concentration as expected. The solvent/solvent radial distribution function, however, showed unexpected changes in shape and intensity as the polymer concentration increased. By using the direct correlation functions from PRISM theory, along with the random phase approximation, we estimated the spinodal temperatures as a function of polymer concentration. PRISM theory, which includes compressibility and nonrandom mixing effects, predicted a significantly higher critical temperature than was obtained from the corresponding incompressible Flory-Huggins theory. The PRISM spinodal curves were in reasonable agreement with experimental dissolution temperatures for octacosane in benzene.

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Self-consistent integral equation theory for polyolefins: Comparison to molecular dynamics simulations and x-ray scattering

Cited by 69 publications

References 37 publications

An analytical coarse-graining method which preserves the free energy, structural correlations, and thermodynamic state of polymer melts from the atomistic to the mesoscale

An analytical coarse-graining method which preserves the free energy, structural correlations, and thermodynamic state of polymer melts from the atomistic to the mesoscale

Structure of Poly(dialkylsiloxane) Melts: Comparisons of Wide-Angle X-ray Scattering, Molecular Dynamics Simulations, and Integral Equation Theory

Integral Equation Theory of Polymer Solutions: Application to Polyethylene/Benzene Solutions

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