Monte Carlo Simulation of Strain-Enhanced Stereocomplex Polymer Crystallization

Guan, Xinchao; Wang, Jiping; Hu, Wenbing

doi:10.1021/acs.jpcb.8b07499

Cited by 22 publications

(16 citation statements)

References 34 publications

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“…Molecular simulations have demonstrated that under the same thermodynamic circumstances homocrystals grow faster than stereocomplex crystals, 4 but strain-induced crystallization enhances the preference of primary nucleation of stereocomplex crystals. 5 If the chain lengths are too small to make chain folding, intermolecular crystal nucleation becomes dominant and benefits stereocomplex crystals. 6 In practice, stereocomplex crystals hold the melting points higher by 50 °C than homocrystals, nevertheless, stereocomplex crystals are commonly harvested in the low and moderate molecular weights of racemic blends due to their higher supercooling than homocrystals, not yet in the high molecular weight blends common for the commercial products.…”

Section: Introductionmentioning

confidence: 99%

“…Another evidence for competition is the polymorphic crystallization of stereocomplex and homocrystals in racemic poly(lactic acid) (PLA) blends, since intramolecular crystal nucleation is favored more by homocrystals of the same species than by stereocomplex crystals of alternatingly packed enantiomeric polymers. Molecular simulations have demonstrated that under the same thermodynamic circumstances homocrystals grow faster than stereocomplex crystals, but strain-induced crystallization enhances the preference of primary nucleation of stereocomplex crystals . If the chain lengths are too small to make chain folding, intermolecular crystal nucleation becomes dominant and benefits stereocomplex crystals .…”

Section: Introductionmentioning

confidence: 99%

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Tammann Analysis of the Molecular Weight Selection of Polymorphic Crystal Nucleation in Symmetric Racemic Poly(lactic acid) Blends

Liú

Wang

et al. 2022

Macromolecules

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High molecular weights switch the harvests of crystallinity from stereocomplex crystals to homocrystals in the symmetric racemic poly(lactic acid) (PLA) blends. We performed Flash DSC measurement of isothermal crystallization kinetics of symmetric racemic PLA blends with five molecular weights in combination with confocal Raman spectroscopy to identify their polymorphic crystal phases. The results confirmed crystallization kinetics as responsible for the molecular weight selection of polymorphic crystals. We further employed Tammann analysis on the crystal nucleation kinetics in the low-temperature region to reveal that higher molecular weights have little influence on homocrystal nucleation; rather, they suppress the nucleation rates of stereocomplex crystals, making homocrystals dominant. The observation was interpreted by the correlation hole of neighboring monomers among higher molecular weight polymers, which hinders intermolecular nucleation of alternatingly racemic polymers as favored for stereocomplex crystals.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tammann Analysis of the Molecular Weight Selection of Polymorphic Crystal Nucleation in Symmetric Racemic Poly(lactic acid) Blends

Liú

Wang

et al. 2022

Macromolecules

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“…Monte Carlo has also been used to study the kinetics and morphology of polymers undergoing crystallization under an applied 3-d flow [131], or strain-enhanced stereo-complex polymer crystallization [132]. In another study [133], the method was extended to binary blends of symmetric crystallizable polymers in which the authors enhanced (separately) the driving forces leading to polymer-uniform and polymer-staggered crystals.…”

Section: Polymer Crystallizationmentioning

confidence: 99%

Using Monte Carlo to Simulate Complex Polymer Systems: Recent Progress and Outlook

Mavrantzas

2021

Front. Phys.

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Metropolis Monte Carlo has been employed with remarkable success over the years to simulate the dense phases of polymer systems. Owing, in particular, to the freedom it provides to accelerate sampling in phase space through the clever design and proper implementation of even unphysical moves that take the system completely away from its natural trajectory, and despite that it cannot provide any direct information about dynamics, it has turned to a powerful simulation tool today, often viewed as an excellent alternative to the other, most popular method of Molecular Dynamics. In the last years, Monte Carlo has advanced considerably thanks to the design of new moves or to the efficient implementation of existing ones to considerably more complex systems than those for which these were originally proposed. In this short review, we highlight recent progress in the field (with a clear emphasis in the last 10 years or so) by presenting examples from applications of the method to several systems in Soft Matter, such as polymer nanocomposites, soft nanostructured materials, confined polymers, polymer rings and knots, hydrogels and networks, crystalline polymers, and many others. We highlight, in particular, extensions of the method to non-equilibrium systems (e.g., polymers under steady shear flow) guided by non-equilibrium thermodynamics and emphasize the importance of hybrid modeling schemes (e.g., coupled Monte Carlo simulations with field theoretic calculations). We also include a short section discussing some key remaining challenges plus interesting future opportunities.

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“…The same simulation technique was used by Gu et al who studied the effects of nanoparticles on polymer crystallization in polymer solutions, focusing on filler dimension and size 26 . Guan et al performed dynamic Monte Carlo simulations to investigate strain‐induced polymer crystallization 27 . Recently, Verho et al studied the crystal growth of PE by molecular dynamics (MD) simulations 28 .…”

Section: Previous Work On Crystallizationmentioning

confidence: 99%

Molecular dynamics simulations of stretch‐induced crystallization in layered polyethylene

Romanos

Megariotis

Theodorou

2021

Polymer Crystallization

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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.

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Monte Carlo Simulation of Strain-Enhanced Stereocomplex Polymer Crystallization

Cited by 22 publications

References 34 publications

Tammann Analysis of the Molecular Weight Selection of Polymorphic Crystal Nucleation in Symmetric Racemic Poly(lactic acid) Blends

Tammann Analysis of the Molecular Weight Selection of Polymorphic Crystal Nucleation in Symmetric Racemic Poly(lactic acid) Blends

Using Monte Carlo to Simulate Complex Polymer Systems: Recent Progress and Outlook

Molecular dynamics simulations of stretch‐induced crystallization in layered polyethylene

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