Simulation of Individual Polymer Chains and Polymer Solutions with Smoothed Dissipative Particle Dynamics (original) (raw)
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Dissipative particle dynamics simulations of a single isolated polymer chain in a dilute solution
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In this study, we investigate the suitability of dissipative particle dynamics (DPD) simulations to predict the dynamics of polymer chains in dilute polymer solutions, where the chain is represented by a set of beads connected by almost inextensible springs. In terms of behaviour, these springs closely mimic rods that serve as representations of Kuhn steps. We find that the predictions depend on the value of the repulsive parameter for bead-bead pairwise interactions used in the DPD simulations ($a_{ij}$). For all systems, the chain sizes and the relaxation time spectrum are analyzed. For aij=0a_{ij} = 0aij=0, theta solvent behaviour is obtained for the chain size, whereas the dynamics at equilibrium agrees well with the predictions of the Zimm model. For higher values of aija_{ij}aij, the static properties of the chain show good solvent behaviour. However, the scaling laws for the chain dynamics at equilibrium show wide variations, with consistent results obtained only at an intermediate value...
Computer simulation of dilute polymer solutions with the dissipative particle dynamics method
Journal of Rheology, 1995
A novel method of investigating the link between molecular features of polymer molecules and the rheological properties of dilute polymer solutions has been investigated. It applies the dissipative particle dynamics (DPD) computer simulation technique, which introduces a lattice-gas automata time-stepping procedure into a molecular-dynamics scheme, to model bead-and-spring-type representations of polymer chains. Investigations of static and dynamic scaling relationships show that the scaling of radius of gyration and relaxation time with the number of beads are consistent with the predictions of the Rouse-Zimm model. Both hydrodynamic interaction and excluded volume emerge naturally from the DPD polymer model, indicating that a realistic description of the dynamics of a dilute polymer solution can be obtained within this framework, and that very efficient computer simulations are possible. 0 1995 Society of Rheology.
Computer simulation of the static and dynamic properties of a polymer chain
Macromolecules, 1981
We have carried out computer simulations of the statics and dynamics of an isolated model polymer chain with excluded volume in a solvent acting as a heat bath. We.find that the disbri~tion function for the separation of a pair of beads scales as the number of beads N to the power v and that edge effects are smalle The dynamical correlation functions, such as that of the 2V+l end-to-end vector, scale as N with v ~ 0.6. The results of a dynamical lattice polymer model are shown to be consistent with the present results if one adjusts the time scales in such a way that the center of mass diffuses at the same rate in the two models. The relaxation of the.stress tensor, is shown to be quite similar to that of the Rouse model. Finally, it is shown that edge effects are much more pronounced in the diffusive motion of the individual beads, there being a skin comprising about 30% of the total polyme where bead motion is relatively quicker.
Dissipative Particle Dynamics Simulations of Polymersomes
Journal of Physical Chemistry B, 2005
A DPD model of PEO-based block copolymer vesicles in water is developed by introducing a new density based coarse graining and by using experimental data for interfacial tension. Simulated as a membrane patch, the DPD model is in excellent agreement with experimental data for both the area expansion modulus and the scaling of hydrophobic core thickness with molecular weight. Rupture simulations of polymer vesicles, or "polymersomes", are presented to illustrate the system sizes feasible with DPD. The results should provide guidance for theoretical derivations of scaling laws and also illustrate how spherical polymer vesicles might be studied in simulation.
Smoothed dissipative particle dynamics model for polymer molecules in suspension
Physical Review E, 2008
We present a model for a polymer molecule in solution based on smoothed dissipative particle dynamics ͑SDPD͒ ͓Español and Revenga, Phys. Rev. E 67, 026705 ͑2003͔͒. This method is a thermodynamically consistent version of smoothed particle hydrodynamics able to discretize the Navier-Stokes equations and, at the same time, to incorporate thermal fluctuations according to the fluctuation-dissipation theorem. Within the framework of the method developed for mesoscopic multiphase flows by Hu and Adams ͓J. Comput. Phys. 213, 844 ͑2006͔͒, we introduce additional finitely extendable nonlinear elastic interactions between particles that represent the beads of a polymer chain. In order to assess the accuracy of the technique, we analyze the static and dynamic conformational properties of the modeled polymer molecule in solution. Extensive tests of the method for the two-dimensional ͑2D͒ case are performed, showing good agreement with the analytical theory. Finally, the effect of confinement on the conformational properties of the polymer molecule is investigated by considering a 2D microchannel with gap H varying between 1 and 10 m, of the same order as the polymer gyration radius. Several SDPD simulations are performed for different chain lengths corresponding to N = 20-100 beads, giving a universal behavior of the gyration radius R G and polymer stretch X as functions of the channel gap when normalized properly.
We introduce a framework for model reduction of chain models for dissipative particle dynamics (DPD) simulations, where the characteristic size of the chain, pressure, density, and temperature are preserved. The proposed methodology reduces the number of degrees of freedom required to represent a particular system with complex molecules (e.g., linear polymers). Based on geometrical considerations we map fine-grained models to a reference state through a consistent scaling of the system, where short length and fast time scales are disregarded while the properties governing the phase equilibria are preserved. Following this coarse-graining process we consistently represent high molecular weight DPD chains (i.e., ≥ 200 beads per chain) with a significant reduction in the number of particles required (i.e., ≥ 20 times the original system).
The Hydrodynamic Interaction in Polymer Solutions Simulated with Dissipative Particle Dynamics
2006
We analyzed extensively the dynamics of polymer chains in solutions simulated with dissipative particle dynamics (DPD), with a special focus on the potential influence of a low Schmidt number of a typical DPD fluid on the simulated polymer dynamics. It has been argued that a low Schmidt number in a DPD fluid can lead to underdevelopment of the hydrodynamic interaction in polymer solutions. Our analyses reveal that equilibrium polymer dynamics in dilute solution, under a typical DPD simulation conditions, obey the Zimm model very well. With a further reduction in the Schmidt number, a deviation from the Zimm model to the Rouse model is observed. This implies that the hydrodynamic interaction between monomers is reasonably developed under typical conditions of a DPD simulation. Only when the Schmidt number is further reduced, the hydrodynamic interaction within the chains becomes underdeveloped. The screening of the hydrodynamic interaction and the excluded volume interaction as the polymer volume fraction is increased are well reproduced by the DPD simulations. The use of soft interaction between polymer beads and a low Schmidt number do not produce noticeable problems for the simulated dynamics at high concentrations, except that the entanglement effect which is not captured in the simulations.
The Dynamics of Polymer Chains in Solution
New Trends in Nonionic (Co)Polymers and Hybrids, 2006
The physical properties and processing behavior of polymers are related to the broad range of length and times scales over which dynamical processes occur. The theory has undergone significant evolution over the last decades due to the introduction of new methods and concepts that have extended the frontier from dilute solutions, in which polymers move independently, to concentrated solutions, where many macromolecules entangle. The aim of this chapter is to review briefly the background of polymer dynamics in solution and to provide the recent achievements in this field. A good understanding of polymer dynamics in solution and the possibility to predict their behavior under flow in different media may help out to a large extent to the synthesis of high-performance polymers, with tailored properties.
Molecular dynamics (MD) is a powerful technique for computing the equilibrium and dynamical properties of classical many-body systems. Over the last fifteen years, due to the rapid development of computers, polymeric systems have been the subject of intense study with MD simulations [1]. At the heart of this technique is the solution of the classical equations of motion, which are integrated numerically to give information for the positions and velocities of atoms in the system [2], [3], [4]
Hydrodynamic interaction in polymer solutions simulated with dissipative particle dynamics
The Journal of Chemical Physics, 2007
We analyzed extensively the dynamics of polymer chains in solutions simulated with dissipative particle dynamics (DPD), with a special focus on the potential influence of a low Schmidt number of a typical DPD fluid on the simulated polymer dynamics. It has been argued that a low Schmidt number in a DPD fluid can lead to underdevelopment of the hydrodynamic interaction in polymer solutions. Our analyses reveal that equilibrium polymer dynamics in dilute solution, under a typical DPD simulation conditions, obey the Zimm model very well. With a further reduction in the Schmidt number, a deviation from the Zimm model to the Rouse model is observed. This implies that the hydrodynamic interaction between monomers is reasonably developed under typical conditions of a DPD simulation.