Ordering and Crystallization of Entangled Polyethylene Melts under Uniaxial Tension: A Molecular Dynamics Study

Sliozberg, Yelena R.; Yeh, In‐Chul; Kröger, Martin; Masser, Kevin A.; Lenhart, Joseph L.; Andzelm, Jan

doi:10.1021/acs.macromol.8b01538

Cited by 57 publications

(66 citation statements)

References 62 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As we have demonstrated above, the application of force increases the entanglement length in the reference (melt) state up to a factor of two in our simulations, see Figure 3 . This is in agreement with previous simulations in uniaxially deformed melts [ 21 ]. Therefore, the force-induced reduction of the primitive path offers an alternative explanation for the strong increase of the stem length at isothermal conditions.…”

Section: Simulation Resultssupporting

confidence: 94%

“…The influence on the topological state is essential: The entanglement length as estimated by the PPA increases up to a factor of two. A comparable result has been obtained in the previous work of Sliozberg et al [ 21 ] simulating uniaxial extension of a coarse-grained PE melt.…”

Section: Simulation Resultssupporting

confidence: 90%

“…In a recent work by Liu and Yu [ 20 ], for instance, it was shown that control over the entanglement state using a complex shear-rate protocol can reveal its central role for the crystallization properties of polycaprolactone (PCL) and blends of PCL/poly(styrene-co-acrylonitrile). Recent coarse-grained simulations of polymer melts subject to a high shear rate and subsequent strong extension of the chains have indicated a significant decrease of the entanglement density [ 21 ].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Crystallization of Polymers under the Influence of an External Force Field

Payal

Sommer

2021

Polymers

View full text Add to dashboard Cite

We simulated the crystallization and melting behavior of entangled polymer melts using molecular dynamics where each chain is subject to a force dipole acting on its ends. This mimics the deformation of chains in a flow field but represents a well-defined equilibrium system in the melt state. Under weak extension within the linear response of the chains, the mechanical work done on the system is about two orders of magnitude smaller as compared with the heat of fusion. As a consequence, thermodynamic and simple arguments following the secondary nucleation model predict only small changes of the crystalline phase. By contrast, an increase of the stem length up to a factor of two is observed in our simulations. On the other hand, the lamellar thickening induced by the external force is proportional to the increase of the entanglement length in the melt prior to crystallization as measured by the primitive path method. While the mechanical work done on the system is only a small perturbation for thermodynamics of polymer crystallization, the change of the primitive path is large. This suggests that a strong increase in the lamellar thickness induced, by external deformation, a topological rather than a thermodynamic origin.

show abstract

Section: Simulation Resultssupporting

confidence: 94%

Section: Simulation Resultssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Crystallization of Polymers under the Influence of an External Force Field

Payal

Sommer

2021

Polymers

View full text Add to dashboard Cite

show abstract

“…As such, polymer crystallization is being increasingly probed with in silico tools, particularly Molecular Dynamics (MD) simulations, which provide fine-grain access in both time and space to the molecular-level details of polymer crystallization (e.g., see ref. 5,6,9,10,12,13,42,43).…”

Section: 2 Sincementioning

confidence: 99%

Divining the shape of nascent polymer crystal nuclei

Hall

Sirk

Percec

et al. 2019

The Journal of Chemical Physics

View full text Add to dashboard Cite

We demonstrate that nascent polymer crystals (i.e., nuclei) are anisotropic entities, with neither spherical nor cylindrical geometry, in contrast to previous assumptions. In fact, cylindrical, spherical, and other high symmetry geometries are thermodynamically unfavorable. Moreover, post-critical transitions are necessary to achieve the lamellae that ultimately arise during the crystallization of semicrystalline polymers. We also highlight how inaccurate treatments of polymer nucleation can lead to substantial errors (e.g., orders of magnitude discrepancies in predicted nucleation rates). These insights are based on quantitative analysis of over four million crystal clusters from the crystallization of prototypical entangled polyethylene melts. New comprehensive bottom-up models are needed to capture polymer nucleation.

show abstract

“…They observed a multistep nucleation process focusing mainly on the nucleation and crystallization process of the stretched PE 29 . Sliozberg and co‐workers studied ordering and crystallization of entangled PE melts under uniaxial tension using different strain rates as well, showing that chain ends are expelled from nascent polymer crystals 30 . Luo and co‐workers studied polymer crystallization under confinement using bare and grafted walls.…”

Section: Previous Work On Crystallizationmentioning

confidence: 99%

Molecular dynamics simulations of stretch‐induced crystallization in layered polyethylene

Romanos

Megariotis

Theodorou

2021

Polymer Crystallization

View full text Add to dashboard Cite

We study, via united atom molecular dynamics (MD) simulations, the crystallization of six polyethylene (PE) systems, each consisting of alternating layers of molten linear polymer of two different degrees of polymerization, under stretch, while at the same time comparing against the corresponding results from two homogeneous monodisperse systems. The “slab,” out of which the model bidisperse layered systems are formed by applying periodic boundary conditions, is comprised of two different molten film subsystems, both of initial thickness 3.66 nm in the z‐direction, adhering to each other; in the first the chain length is 200 carbon atoms and in the second 400 carbon atoms. Following a short pre‐equilibration at 350 K and 1 bar, a stretching simulation is conducted in the NėxxLyPzzT ensemble, with the engineering strain rate ėxx fixed in the machine (pulling) direction x, parallel to the interfaces; the width of the films Ly fixed in the transverse direction; and the pressure Pzz normal to the interfaces fixed at 1 bar. The temperature during stretching is held constant at T = 300 K, corresponding to more than 100 K subcooling for both molar masses. Deformation to a stretch ratio of Lxx/Lxx,0 = 2.6 within 120 ns is followed by annealing according to two different protocols. In the first protocol, stretching is stopped and the systems allowed to relax in the NLxLyPzzT ensemble under Pzz = 1 bar for 60 ns. In the second protocol, stretching is continued at a rate 10 times lower than the initial one for 60 ns and then stopped, letting the systems relax for 100 ns. Crystallization is observed following both protocols. A nucleus of ordered material emerges early on during the first stage of stretching at a deformation rate of 0.05 nm/ns. The crystalline structure is sharper and more extended following the second, slower protocol. Crystallized macromolecules lie in planes almost parallel to the interface, forming a tilt angle of 20° to 24° with the pulling direction. Long and short chains co‐crystallize into lamellae, which are slightly more extended in the long‐chain regions. This study sheds light on the morphology expected to be developed in monomaterial packaging consisting of oriented bidisperse PE layers, designed to combine low permeability with recyclability and low‐environmental impact.

show abstract

Ordering and Crystallization of Entangled Polyethylene Melts under Uniaxial Tension: A Molecular Dynamics Study

Cited by 57 publications

References 62 publications

Crystallization of Polymers under the Influence of an External Force Field

Crystallization of Polymers under the Influence of an External Force Field

Divining the shape of nascent polymer crystal nuclei

Molecular dynamics simulations of stretch‐induced crystallization in layered polyethylene

Contact Info

Product

Resources

About