Dynamics of Polystyrene Melts through Hierarchical Multiscale Simulations

Harmandaris, Vagelis; Kremer, Kurt

doi:10.1021/ma8018624

Cited by 203 publications

(327 citation statements)

References 83 publications

Supporting

Mentioning

296

Contrasting

Unclassified

Order By: Relevance

“…In previous works we have studied extensively the PS model predictions for structure, dimensions and dynamics of PS systems as a function of molecular weight. 39,40 …”

Section: B Polystyrene Modelmentioning

confidence: 99%

Molecular dynamics of polyisoprene/polystyrene oligomer blends: The role of self-concentration and fluctuations on blend dynamics

Harmandaris

Doxastakis

2013

The Journal of Chemical Physics

View full text Add to dashboard Cite

1The effect of self-concentration and intermolecular packing on the dynamics of polyisoprene (PI)/polystyrene (PS) blends is examined by extensive atomistic simulations. Direct information on local structure of the blend system allows a quantitative calculation of self-and effective composition terms at various length scales that are introduced to proposed models of blend dynamics. Through a detailed statistical analysis, the full distribution of relaxation times associated with reorienation of carbon-hydrogen bonds was extracted and compared to literature experimental data. A direct relation between relaxation times and local effective composition is found. Following an implementation of a model involving local composition as well as concentration fluctuations the relevant length scales characterizing the segmental dynamics of both components were critically examined. For PI the distribution of times becomes narrower for the system with the lowest PS content and then broadens as more PS is added. This is in contrast to the slow component (PS), where an extreme breadth is found for relaxation times in the 25/75 system prior to narrowing as we increase PI concentration. The chain dynamics was directly quantified by diffusion coefficients as well as the terminal (maximum) relaxation time of each component in the mixed state. Strong coupling between the friction coefficients of the two components was predicted that leads to very similar chain dynamics for PI and PS, particularly for high concentrations of PI. We anticipate this finding to the rather short oligomers (below the Rouse regime) studied here as well as to the rather similar size of PI and PS chains. The ratio of the terminal to the segmental relaxation time, τ term /τ seg,c , presents a clear qualitative difference for the constituents: for PS the above ratio is almost independent of blend composition and very similar to the pure state. In contrast, for PI this ratio depends strongly on the composition of the blend;i.e. the terminal relaxation time of PI increases more than its segmental relaxation time, as the concentration of PS increases, resulting into a larger terminal/segmental ratio. We explain this disparity, based on the different length scales characterizing dynamics. The relevant length for the segmental dynamics of PI is about 0.4-0.6 nm, smaller than chain dimensions which are expected to characterize terminal dynamics, whereas for PS associated length scales are similar (about 0.7-1.0 nm) rendering a uniform change with mixing.2

show abstract

“…In previous works we have studied extensively the PS model predictions for structure, dimensions and dynamics of PS systems as a function of molecular weight. 39,40 …”

Section: B Polystyrene Modelmentioning

confidence: 99%

Molecular dynamics of polyisoprene/polystyrene oligomer blends: The role of self-concentration and fluctuations on blend dynamics

Harmandaris

Doxastakis

2013

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…To succeed this, a hierarchical multi scale methodology (Harmandaris et al 2009;Harmandaris et al 2010) is necessary, which involves density functional theory (DFT), classical molecular dynamics (MD) as well as mesoscopic coarse-grained dynamics simulations (Johnson et al 2011). The overall methodology will allow us to provide a fundamental study of the coupling between microstructure at the interface and macroscopic properties (structural, mechanical, elastic and dynamical-rheological) of graphene/polymer nanocomposite systems.…”

Section: Introductionmentioning

confidence: 99%

Structure and dynamics of poly(methyl methacrylate)/graphene systems through atomistic molecular dynamics simulations

Rissanou

Harmandaris

2013

J Nanopart Res

View full text Add to dashboard Cite

The main goal of the present work is to examine the effect of graphene layers on the structural and dynamical properties of polymer systems. We study hybrid poly(methyl methacrylate) (PMMA)/graphene interfacial systems, through detailed atomistic molecular dynamics (MD) simulations. In order to characterize the interface, various properties related to density, structure and dynamics of polymer chains are calculated, as a function of the distance from the substrate. A series of different hybrid systems, with width ranging between [2. 60 -13.35] nm, are being modeled. In addition, we compare the properties of the macromolecular chains to the properties of the corresponding bulk system at the same temperature. We observe a strong effect of graphene layers on both structure and dynamics of the PMMA chains. Furthermore the PMMA/graphene interface is characterized by different length scales, depending on the actual property we probe:Density of PMMA polymer chains is larger than the bulk value, for polymer chains close

show abstract

“…In the latter case it is often sufficient to simply scale the unit of time in order to obtain the correct diffusion coefficient. 21,22 A nice aspect of the method is that it takes into account the chemical nature of the polymer.…”

Section: Introductionmentioning

confidence: 99%

Chain dynamics of poly(ethylene-alt-propylene) melts by means of coarse-grained simulations based on atomistic molecular dynamics

Pérez-Aparicio

Colmenero

Álvarez

et al. 2010

The Journal of Chemical Physics

View full text Add to dashboard Cite

We present coarse-grained molecular dynamics simulations of poly͑ethylene-alt-propylene͒ ͑PEP͒ melts, ranging in chain length from about N e ͑the entanglement length͒ to N =6N e . The coarse-grained parameters, potential of mean force and bare friction, were determined from fully atomistic molecular dynamics simulations carried out on a PEP cell containing 12 chains of 80 monomers each and subjected to periodic boundary conditions. These atomistic simulations were previously validated by means of extensive neutron scattering measurements. Uncrossability constrains were also introduced in the coarse-grained model to prevent unphysical bond crossing. The coarse-grained simulations were carried out at 492 K and focus on chain dynamics. The results obtained were analyzed in terms of Rouse coordinates and Rouse correlators. We observe deviations from Rouse behavior for all chain lengths investigated, even when the chain stiffness is incorporated in the Rouse model. These deviations become more important as the chain length increases. The general scenario emerging from the results obtained is that the deviations from Rouse-like behavior are due to correlations among the forces acting upon a chain bead, which seem to be related with the constraint of uncrossability among the chains. As consequence, nonexponentiality of the Rouse correlators and mode-and time-dependent friction are observed. It seems that, in the molecular weight explored, these effects still give not raise to reptation behavior but to a crossover regime between Rouse and reptation. On the other hand, the results obtained are in qualitative agreement with those expected from the so-called generalized Rouse models, based on memory function formalisms.

show abstract

Dynamics of Polystyrene Melts through Hierarchical Multiscale Simulations

Cited by 203 publications

References 83 publications

Molecular dynamics of polyisoprene/polystyrene oligomer blends: The role of self-concentration and fluctuations on blend dynamics

Molecular dynamics of polyisoprene/polystyrene oligomer blends: The role of self-concentration and fluctuations on blend dynamics

Structure and dynamics of poly(methyl methacrylate)/graphene systems through atomistic molecular dynamics simulations

Chain dynamics of poly(ethylene-alt-propylene) melts by means of coarse-grained simulations based on atomistic molecular dynamics

Contact Info

Product

Resources

About