Atomistic simulation of energetic and entropic elasticity in short-chain polyethylenes

IONESCU, Tudor; Mavrantzas, Vlasis G.; Keffer, David J.; Edwards, Brian J.

doi:10.1122/1.2838250

Cited by 18 publications

(38 citation statements)

References 45 publications

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“…This linear behavior of temperature change with tr(c) was first noticed by Ionescu et al [59,60] in an experimental study of high-density polyethylene (HDPE), where data taken at three different temperatures revealed linear behavior that superimposed, as above, to reveal a common value of the slope. This remarkable result was rationalized based upon a simple expression for the extended internal energy to include conformational effects, Fig.…”

Section: Configurational Temperaturementioning

confidence: 64%

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Atomistic simulation of crystallization of a polyethylene melt in steady uniaxial extension

Baig

Edwards

2010

Journal of Non-Newtonian Fluid Mechanics

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Section: Configurational Temperaturementioning

confidence: 64%

“…A "nonequilibrium temperature," T NE , was then derived by taking the partial derivative of Eq. (17) with respect to entropy [59,60],…”

Section: Configurational Temperaturementioning

confidence: 99%

Atomistic simulation of crystallization of a polyethylene melt in steady uniaxial extension

Baig

Edwards

2010

Journal of Non-Newtonian Fluid Mechanics

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“…Generally, Monte Carlo methods do not capture crystallization kinetics, and crystallization from a quiescent melt, regardless of temperature, is too slow to analyze using molecular dynamics (MD); however, the crystallization process is sped up dramatically through strong orientation and stretching [34][35][36], such as occurs under an elongational flow at high field strength. Such a speedup can occur because the highly stretched and oriented chains can more easily pack into a crystal lattice via energetically favorable sideto-side interactions [37] rather than undergo the kinetically slow chain-folding mechanisms to obtain a similar packing. Nevertheless, even at equilibrium, crystal nucleation events can be captured and analyzed via MD, which can shed light on similar nucleation kinetics induced under flow.…”

Section: Introductionmentioning

confidence: 99%

Flow-induced crystallization of a polyethylene liquid above the melting temperature and its nonequilibrium phase diagram

Sefiddashti

Edwards

Khomami

2020

Phys. Rev. Research

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Manufacturing of plastics is typically performed via flow processing of a polymer melt. Semicrystalline polymers, such as polyethylene (PE), play a critical role in the global plastics markets, but fundamental understanding of how process flow conditions affect their properties is lacking. Nonequilibrium molecular dynamics of a PE liquid above its melting point revealed reversible transitions from coiled, biphasic, stretched, pretransitional, and crystalline phases with applied stress in elongational flow. A nonequilibrium phase diagram was developed for the thermodynamic state space.

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“…From a thermodynamic viewpoint, this occurs as a result of the relative increase in the energetic effect over the entropic one on the system structure with decreasing temperature. 40,41 Alternatively, such ordered structures can also be induced by subjecting the system to an external flow field. Assuming T conf to represent the overall structure of polyethylene systems, it is therefore physically reasonable to expect that ⌬T conf of the system would generally be negative under an external flow field as it induces the ordering of the system structure.…”

Section: B Nemd Simulations Of Polymeric Fluidsmentioning

confidence: 99%

Analysis of the configurational temperature of polymeric liquids under shear and elongational flows using nonequilibrium molecular dynamics and Monte Carlo simulations

Baig

Edwards

2010

The Journal of Chemical Physics

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Rheological and structural studies of liquid decane, hexadecane, and tetracosane under planar elongational flow using nonequilibrium molecular-dynamics simulations J. Chem. Phys. 122, 184906 (2005) We present a detailed analysis of the configurational temperature ͑T conf ͒ for its application to polymeric materials using nonequilibrium molecular dynamics ͑NEMD͒ and nonequilibrium Monte Carlo ͑NEMC͒ methods. Simulations were performed of linear polyethylene liquid C 78 H 158 undergoing shear and elongational flows. At equilibrium, T conf is equal to the set point temperature of the simulation. An aphysically large decrease in T conf is observed in the NEMD simulations for both flows, especially at strong flow fields. By analyzing separately the individual contributions of the different potential interaction modes to the configurational temperature, it is found that the bonded modes ͑which constitutes almost 99.5% of the total͒ dominate the total T conf over the nonbonded ones; i.e., bond-stretching ͑Ϸ86.5%͒, bond-bending ͑Ϸ11.8%͒, bond-torsional ͑Ϸ1.2%͒, nonbonded intermolecular ͑Ϸ0.4%͒, and intramolecular ͑Ϸ0.1%͒ Lennard-Jones. The configurational temperature of the individual modes generally exhibits a nonmonotonic behavior with the flow strength and a dramatic change beyond a critical value of flow strength; this is mainly attributed to the dynamical effect of strong molecular collisions occurring at strong flow fields. In contrast, no such behavior is observed in the NEMC simulations where such dynamical effects are absent. Based on the principal physical concept of the configurational temperature, which represents the large-scale structural characteristics of the system, we propose to exclude the dynamical effects exhibited by the individual interaction modes, in obtaining a physically meaningful T conf as the configurational entropy of the system should not be affected by such factors. Since ͑a͒ the main difference between equilibrium and nonequilibrium states lies in the change in the overall ͑global͒ structure ͑represented by the bond torsional and nonbonded modes͒, and ͑b͒ the local, very short structure ͑represented by the bond-stretching and bond-bending modes͒ is barely changing between equilibrium and nonequilibrium states and its contribution to the total system configurational entropy is negligible compared to the large-scale structural changes, in order to accurately describe the structural changes occurring at nonequilibrium states by use of the configurational temperature, we further propose that only the contributions from the bond-torsional and nonbonded modes to ⌬T conf between equilibrium and nonequilibrium states should be taken into account to generate a physically meaningful ⌬T conf . Applying the above hypothesis to the analysis of the simulation data, good agreement between the NEMD and NEMC simulations ͑and between NEMD simulations for different flows͒ is observed. Furthermore, the configurational temperature obtained in such way is found to match remarkably well with the heat capacity...

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Atomistic simulation of energetic and entropic elasticity in short-chain polyethylenes

Cited by 18 publications

References 45 publications

Atomistic simulation of crystallization of a polyethylene melt in steady uniaxial extension

Atomistic simulation of crystallization of a polyethylene melt in steady uniaxial extension

Flow-induced crystallization of a polyethylene liquid above the melting temperature and its nonequilibrium phase diagram

Analysis of the configurational temperature of polymeric liquids under shear and elongational flows using nonequilibrium molecular dynamics and Monte Carlo simulations

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