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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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Polymeric materials display distinguished characteristics which stem from the interplay of phenomena at various length and time scales. Further development of polymer systems critically relies on a comprehensive understanding of the fundamentals of their hierarchical structure and behaviors. As such, the inherent multiscale nature of polymer systems is only reflected by a multiscale analysis which accounts for all important mechanisms. Since multiscale modelling is a rapidly growing multidisciplinary field, the emerging possibilities and challenges can be of a truly diverse nature. The present review attempts to provide a rather comprehensive overview of the recent developments in the field of multiscale modelling and simulation of polymeric materials. In order to understand the characteristics of the building blocks of multiscale methods, first a brief review of some significant computational methods at individual length and time scales is provided. These methods cover quantum mechanical scale, atomistic domain (Monte Carlo and molecular dynamics), mesoscopic scale (Brownian dynamics, dissipative particle dynamics, and lattice Boltzmann method), and finally macroscopic realm (finite element and volume methods). Afterwards, different prescriptions to envelope these methods in a multiscale strategy are discussed in details. Sequential, concurrent, and adaptive resolution schemes are presented along with the latest updates and ongoing challenges in research. In sequential methods, various systematic coarse-graining and backmapping approaches are addressed. For the concurrent strategy, we aimed to introduce the fundamentals and significant methods including the handshaking concept, energy-based, and force-based coupling approaches. Although such methods are very popular in metals and carbon nanomaterials, their use in polymeric materials is still limited. We have illustrated their applications in polymer science by several examples hoping for raising attention towards the existing possibilities. The relatively new adaptive resolution schemes are then covered including their advantages and shortcomings. Finally, some novel ideas in order to extend the reaches of atomistic techniques are reviewed. We conclude the review by outlining the existing challenges and possibilities for future research.
... 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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Scitation is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies
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Thesis (doctoral)--Technische Universiteit Eindhoven, 2002.
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Thesis--Technische Hogeschool Delft. Vita. An authorized xerographic copy (N78-71340) reproduced by the National Technical Information Service of the U.S. Dept. of Commerce for the National Aeronautics and Space Administration. Includes bibliographical references and indexes.
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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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