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ABSTRACT: We extend our generalized Langevin equation for cooperative dynamics (CDGLE), a many-chain approach, to investigate liquids composed of macromolecules with different local chemical structure. In particular, the specific role of semiflexibility and local architecture on the overall polymer dynamics is explored. The theory predicts centre-of-mass diffusion in good agreement with simulations for liquids of macromolecules with slightly branched monomeric architectures.
Journal of Physics Condensed Matter 04/2007; 19(20):205115. · 2.55 Impact Factor
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ABSTRACT: Starting from the Ornstein-Zernike equation the authors derive an analytical theory, at the level of pair correlation functions, which coarse grains polymer melts into liquids of interacting soft colloidal particles. Since it is analytical, the presented coarse-graining approach will be useful in developing multiscale modeling procedures to simulate complex fluids of macromolecules. The accuracy of the theory is tested by its capacity to reproduce the liquid structure, as given by the center-of-mass intermolecular total pair correlation function. The theory is found to agree well with the structure predicted by molecular dynamics simulations of the liquid described at the united atom level as well as by molecular dynamics simulations of the liquid of interacting colloidal particles. The authors perform simulations of the liquid of interacting colloidal particles having as input the potential obtained from their analytical total pair correlation function by enforcing the hypernetted-chain closure approximation. Tests systems are polyethylene melts of chains with increasing degrees of polymerization and polymer melts of chains with different chemical architectures. They also discuss the effect of adopting different conventional approximations for intra- and intermolecular monomer structure factors on the accuracy of the coarse-graining procedure, as well as the relevance of higher-order corrections to their expression.
The Journal of Chemical Physics 01/2007; 125(23):234902. · 3.33 Impact Factor
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ABSTRACT: We present a theoretical approach which maps polymer blends onto mixtures of soft-colloidal particles. The analytical mesoscale pair correlation functions reproduce well data from united atom molecular dynamics simulations of polyolefin mixtures without fitting parameters. The theory exactly recovers the analytical expressions for density and concentration fluctuation structure factors of soft-colloidal mixtures (liquid alloys).
The Journal of Chemical Physics 03/2005; 122(5):54907. · 3.33 Impact Factor
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ABSTRACT: An analytical description of polymer melts and their mixtures as liquids of interacting soft colloidal particles is obtained from liquid-state theory. The derived center-of-mass pair correlation functions with no adjustable parameters reproduce those computed from united atom molecular dynamics simulations. The coarse-grained description correctly bridges micro- and mesoscopic fluid properties. Molecular dynamics simulations of soft colloidal particles interacting through the calculated effective pair potentials are consistent with data from microscale simulations and analytical formulas.
Physical Review Letters 01/2005; 93(25):257803. · 7.37 Impact Factor
