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Structure factor and rheology of chain molecules from molecular dynamics
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10.1063/1.4803526
/content/aip/journal/jcp/138/18/10.1063/1.4803526
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/18/10.1063/1.4803526

Figures

Image of FIG. 1.
FIG. 1.

Particle interactions scheme. Dark circles correspond to beads in the chain molecules. Light circles represent solvent particles. Non-bonded particles, including solvent and beads, interact with truncated and shifted Lennard-Jones potential while bonded chains are represented by a FENE + Lennard-Jones potential.

Image of FIG. 2.
FIG. 2.

Structure factor projections on the - plane at . There is isotropy in all cases: (a) 0.0, (b) 0.1, (c) 0.5, and (d) 1.0 solutions.

Image of FIG. 3.
FIG. 3.

Shear viscosity vs. shear rate for the 0.0 (●), 0.1 (▽), 0.5 (▲), and 1.0 (□) solutions. Power law model fits well the simulated data in the shear thinning region, while the Carreau-Yasuda model fits the behavior of simulated data in the whole range of shear rates.

Image of FIG. 4.
FIG. 4.

First normal stress coefficient vs. shear rate for the 0.1 (▽), 0.5 (▲), and 1.0 (□) solutions.

Image of FIG. 5.
FIG. 5.

Second normal stress coefficient vs. shear rate for 0.1 (▽), 0.5 (▲), and 1.0 (□) solutions.

Image of FIG. 6.
FIG. 6.

Ratios of the second and first normal stress coefficients vs. shear rate for the 0.5 (▲) and 1.0 (□) solutions.

Image of FIG. 7.
FIG. 7.

Absolute value of the first normal stress difference vs. shear rate for the 0.0 (●), 0.1 (▽), 0.5 (▲), and 1.0 (□) solutions.

Image of FIG. 8.
FIG. 8.

Structure factor patterns on the - plane of the pure solvent at shear rates of (a) and (b) . Both cases display isotropic behavior.

Image of FIG. 9.
FIG. 9.

Structure factor patterns on the - plane of the 0.1 solution at shear rates of (a) and (b) .

Image of FIG. 10.
FIG. 10.

Structure factor patterns on the - plane of the 0.5 solution at shear rates of (a) and (b) .

Image of FIG. 11.
FIG. 11.

Structure factor patterns on the - plane of pure chains at shear rates of (a) and (b) .

Image of FIG. 12.
FIG. 12.

Evolution of the structure factor patterns on the - plane as a function of the shear rate at the shear-thinning region for the pure chain molecules. (a) , (b) , (c) , (d) , (e) and (f) . Peaks appear as the shear rate increases. The scattering pattern changes are due to molecular organization.

Image of FIG. 13.
FIG. 13.

Mean square radius of gyration as a function of shear rate. The increasing in the value of this parameter with the shear rate evidences the alignment of the chains along the flow. Symbols differentiate chain mass fraction in the solution: 0.1 (▽), 0.5 (▲), and 1.0 (□).

Image of FIG. 14.
FIG. 14.

Scheme to represent the relation between the static structure factor, the chain conformation, and the shear viscosity for the pure chain molecules (melt). The three-dimensional snapshots show the alignment process of the chain molecules with the flow as the shear rate increases. For the sake of clarity not all chains used in calculations are include in the three-dimensional snapshots. Note also the changes in the structure factor patterns as the shear rate increases.

Tables

Generic image for table
Table I.

Dimensionless variables and parameters used in simulation.

Generic image for table
Table II.

Parameters of Power-Law and Carreau-Yasuda models that fit simulation data.

Generic image for table
Table III.

Comparative table of some rheological parameters.

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/content/aip/journal/jcp/138/18/10.1063/1.4803526
2013-05-08
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Structure factor and rheology of chain molecules from molecular dynamics
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/18/10.1063/1.4803526
10.1063/1.4803526
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