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Equilibration and Deformation of Amorphous Polystyrene: Scale‐jumping Simulational Approach

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Abstract

A polymer sample-preparation method (extended-chain condensation, ECC) based solely on molecular-dynamics simulations has been compared to a connectivity-altering Monte Carlo method (coarse-grained end-bridging, CGEB). Since the characteristic ratio for the CGEB samples is closer to the experimental value, ECC results in polymer structures that are too compact. The stress-strain relations are different in the strain-hardening regime. For CGEB samples, a stronger strain hardening is observed and the strain-hardening modulus is more realistic; for the CGEB polystyrene (PS) sample G(R) = 9 +/- 1 MPa is found versus G(R) = 4 +/- 2 MPa for the ECC samples. These differences have to be attributed to a steeper increase in the contributions to the total stress from bond- and dihedral angles for CGEB than for ECC samples.

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... In order to validate the assumption of the isotropic behavior of the PNC, we present in Appendix the nine engineering constants for an orthotropic material, namely E x x , E yy , E zz , G x y , G x z , G yz , ν x y , ν x z and ν yz , which are determined from MD simulations after applying 6 strain rates as boundary conditions on the unit box, namelyε x x ,ε yy ,ε zz ,ε x y ,ε x z andε yz . The simulated stress-strain behavior in Fig. 5 at a strain rate ofε x x = 3 × 10 −6 fs −1 exhibits the same trends as those observed in numerical modeling and experimental testing for amorphous polymers [10,69,78]. This is because we consider temperatures T ≪ T g , so that the effect of the strain rate is not expected to be important. ...
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... The mapping scheme shown in Figure 4c was developed by Qian et al. [353] which yields potentials capable of reproducing the isothermal compressibility as well as structural properties of the PS melts from 400 to 500 K. Finally, in order to include the tacticity effects on the structural and dynamic properties of PS, Harmandaris et al. [354,355] and Fritz et al. [356] used the CG models shown in Figure 4d. This model has been applied to study both the mechanical properties of PS glasses [357,358] and the dynamic properties of PS melts [359,360]. These works manifest the influence of the definition of super atoms on the final outcome of the simulations. ...
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... Interestingly, the time scale factors are not identical for these models [42]. Moreover, the model can be applied to study both the mechanical properties of PS glasses [202,203] and the dynamic properties of PS melts [204,205]. From these studies, it is important to know that although there are different ways to define the super atom in deriving a coarse-grained model, the static, dynamic or thermodynamic properties of the coarse-grained model should be tested and validated before it is further applied [42]. ...
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Thesis (doctoral)--Technische Universiteit Eindhoven, 2002.
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  • R Auhl
  • R Everaers
  • G S Grest
  • K Kremer
  • S J Plimpton
R. Auhl, R. Everaers, G. S. Grest, K. Kremer, S. J. Plimpton, J. Chem. Phys. 2003, 119, 12718.
  • J P Wittmer
  • P Beckrich
  • H Meyer
  • A Cavallo
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