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Theoretical reconstruction of realistic dynamics of highly coarse-grained cis-1,4-polybutadiene melts
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10.1063/1.4792367
/content/aip/journal/jcp/138/12/10.1063/1.4792367
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/12/10.1063/1.4792367

Figures

Image of FIG. 1.
FIG. 1.

Dimensionless monomer friction coefficient as a function of the hard sphere diameter, based on Eq. (6) . (a) cis-1,4-polybutadiene samples with N = 32, 56, 128, 320 (solid, dashed, dotted-dashed, and dotted lines correspondingly) and parameters as reported in Table I and Ref. 15 . (b) Polyethylene samples with N = 30, 44, 96, 270 (solid, dashed, dotted-dashed, and dotted lines correspondingly) and parameters as reported in Refs. 5 and 6 . Horizontal lines represent 1/N values, following the diffusion coefficient for unentangled chains, Dβζ m = 1/N.

Image of FIG. 2.
FIG. 2.

Diffusion coefficient predicted from the rescaled MS MD, when different values of the hard-sphere diameter are chosen as an input to the reconstruction procedure. Assuming different values of d, calculated by enforcing Rouse diffusive behavior for N = 56 (d = 1.4672), 64 (d = 1.4051), or 80 (d = 1.374) (circles, diamond, triangles correspondingly) leads to diffusion coefficients in good agreement with the UA MD simulation data (filled squares).

Image of FIG. 3.
FIG. 3.

Center of mass self-diffusion coefficient as a function of degree of polymerization, N, for cis-1,4-polybutadiene melts with parameters defined in Table I . Diffusion coefficients reconstructed from MS MD by applying our procedure (open symbol) are compared against UA MD data (filled symbol) from Ref. 15 . In analogy with the figure from the source, three scaling regimes in terms of power law dependence of DN b are shown as dashed (b > 1), solid (b ≈ 1), and dotted-dotted-dashed (b ≈ 2) lines.

Image of FIG. 4.
FIG. 4.

Density as a function of degree of polymerization, N, for cis-1,4-polybutadiene samples reported in Table I .

Image of FIG. 5.
FIG. 5.

End-to-end vector time decorrelation function for cis-1,4-polybutadiene with N = 112. Data from UA MD simulations (symbols) are compared with predictions of the theory for cooperative dynamics (solid line) where the number of correlated chains is set to n = 7 and the monomer friction coefficient is reconstructed from MS MD simulations, using the procedure described in this paper.

Image of FIG. 6.
FIG. 6.

Center of mass mean square displacement as a function of time for cis-1,4-polybutadiene samples with N = 240 (circle), 320 (square), and 400 (triangle). Predictions of the theory for cooperative dynamics (solid lines) are compared against the UA MD simulations (symbols). Also shown are the purely diffusive slopes obtained from the rescaled MS MD simulations (dashed lines). Inset illustrates how the uncertainty in the radius-of-gyration affects the mean-square-displacement for the N = 240 sample: the upper and lower values, reported as dot-dashed lines, corresponds to the upper and lower values of R g as reported in Table I .

Image of FIG. 7.
FIG. 7.

Normalized dynamic structure factor for cis-1,4-polybutadiene with N = 96 and q = 0.04 (squares), 0.1 (circles), 0.2 (triangles), 0.3 (diamonds) Å−1. The data from UA MD simulations (symbols) are compared against the cooperative dynamics theory (solid lines) where the number of correlated chains is set to n = 15 and the monomer friction coefficient is reconstructed from MS MD simulations, using the procedure described in this paper.

Image of FIG. 8.
FIG. 8.

Normalized dynamic structure factor for cis-1,4-polybutadiene with N = 400 and q = 0.04 (squares), 0.1 (circles), 0.2 (triangles), 0.3 (diamonds) Å−1. The data from UA MD simulations (symbols) are compared against the theory for cooperative dynamics (solid lines) where the number of correlated chains is set to n = 12 and the monomer friction coefficient is reconstructed from the MS MD simulations, using the procedure described in this paper.

Image of FIG. 9.
FIG. 9.

Monomer mean square displacement, averaged over the innermost chain segments, as a function of time for cis-1,4-polybutadiene with N = 112. Predictions from the theory of cooperative dynamics (solid line) are compared against UA MD simulations (circles). The slope obtained from the rescaled MS MD simulations is shown as well (dotted-dashed line).

Image of FIG. 10.
FIG. 10.

Density dependence of the semiflexibility parameter g calculated from Eq. (19) using values of the radius-of-gyration R g measured in UA MD and reported in Table III .

Image of FIG. 11.
FIG. 11.

Radius of gyration squared over degree of polymerization as a function of N. UA MD data (circles), with statistical error, are compared against data calculated with the Freely Rotating Chain model using an averaged semiflexibility parameter, g = 0.6564 (solid line).

Image of FIG. 12.
FIG. 12.

Diffusion coefficients reconstructed from MS MD simulations using the radius-of-gyration calculated with the freely rotating chain model (open circles) are compared against UA MD data (filled squares). Predictions for new systems with N =180, 280, 360, and 440 are shown as well (open diamonds).

Tables

Generic image for table
Table I.

Simulation parameters for 1,4-cis-PB chains of increasing lengths.

Generic image for table
Table II.

Diffusion coefficient reconstructed from MS MD simulation compared against UA MD simulations.

Generic image for table
Table III.

Semiflexibility parameter g calculated from FRC expression.

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/content/aip/journal/jcp/138/12/10.1063/1.4792367
2013-03-05
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Theoretical reconstruction of realistic dynamics of highly coarse-grained cis-1,4-polybutadiene melts
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/12/10.1063/1.4792367
10.1063/1.4792367
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