Crystal Growth in Polyethylene by Molecular Dynamics: The Crystal Edge and Lamellar Thickness

Verho, Tuukka; Paajanen, Antti; Vaari, Jukka; Laukkanen, Anssi

doi:10.1021/acs.macromol.8b00857

Cited by 54 publications

(72 citation statements)

References 67 publications

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“…This work by Doye and Frenkel also highlighted that the outer layers (i.e., the surfaces of growing crystals) exhibit stem length distributions that are shifted towards short stems. A subsequent characterization [16] of stem length distributions and their evolution in the context of polyethylene crystal growth reinforced and further elucidated that the central mature regions of lamellae can exhibit substantial variations in stem lengths. Still others have extracted system-wide stem length distributions following crystallization (e.g., [21]).…”

Section: Introductionmentioning

confidence: 89%

“…We also performed a substantial detailed analysis of our crystallization simulations to validate the inclusion of the single-bead stems in the current study. For reference, the simulation-based literature on polymer crystallization (e.g., [16,[18][19][20]24,25,28,30,34,38,41,42,48]) does not provide a clear precedent as to whether or not such short stems should be included when analyzing polymer crystallization simulations. In particular, some studies include such short stems [18,24,25,28,38,41,42,48], other studies exclude them by invoking a minimum length criterion [16,21,22,34], and still other studies allow for stems of variable length and use a length criterion to assign some stems as crystalline [19,20,30].…”

Section: Pressure 1 Atmmentioning

confidence: 99%

“…With molecular simulations, one can directly study the molecular-level nanoscopic details of polymer crystal nuclei and stems during polymer crystallization. Previous in silico studies have probed stem-related properties and phenomena during crystallization, including the lamellar thickness of nuclei [14,15], intra-lamellar stem reordering mechanisms [16], stem growth rates as a function of stem length [16,17], the structural details of crystal growth fronts [16,18,19], and connections between average stem lengths and crystallization conditions (e.g., temperature and system composition) [20][21][22][23]. In particular, Doye and Frenkel [24] studied the distribution of stem lengths during the formation of crystalline layers from solution on polymer crystal growth faces of varying thickness, and thereby revealed that stem lengths can vary substantially.…”

Section: Introductionmentioning

confidence: 99%

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Monodisperse Polymer Melts Crystallize via Structurally Polydisperse Nanoscale Clusters: Insights from Polyethylene

et al. 2020

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This study demonstrates that monodisperse entangled polymer melts crystallize via the formation of nanoscale nascent polymer crystals (i.e., nuclei) that exhibit substantial variability in terms of their constituent crystalline polymer chain segments (stems). More specifically, large-scale coarse-grain molecular simulations are used to quantify the evolution of stem length distributions and their properties during the formation of polymer nuclei in supercooled prototypical polyethylene melts. Stems can adopt a range of lengths within an individual nucleus (e.g., ∼1–10 nm) while two nuclei of comparable size can have markedly different stem distributions. As such, the attainment of chemically monodisperse polymer specimens is not sufficient to achieve physical uniformity and consistency. Furthermore, stem length distributions and their evolution indicate that polymer crystal nucleation (i.e., the initial emergence of a nascent crystal) is phenomenologically distinct from crystal growth. These results highlight that the tailoring of polymeric materials requires strategies for controlling polymer crystal nucleation and growth at the nanoscale.

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Section: Introductionmentioning

confidence: 89%

Section: Pressure 1 Atmmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Monodisperse Polymer Melts Crystallize via Structurally Polydisperse Nanoscale Clusters: Insights from Polyethylene

et al. 2020

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“…Larger spherulites appearing in nanocomposites than micron-composites present a much clearer observation of filamentous lamellae aggregation. According to the slip diffusion model of nanodielectrics, the polyethylene molecules with intermediate phase near the surface of BiFeO 3 nanofillers will be relaxed by the BiFeO 3 orienting movement caused by magnetic polarization, and are prone to orderly rearrange at LDPE-melting temperature, eventually crystallizing on lamella surfaces to make lamellae thicker [21][22][23][24].…”

Section: Infrared Spectrummentioning

confidence: 99%

Magnetic and Dielectric Properties of Nano- and Micron-BiFeO3/LDPE Composites with Magnetization Treatments

Song

Fan

et al. 2019

Materials

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By means of magnetization treatments at ambient temperature and elevated temperatures, the nano- and micron-bismuth ferrate/low density polyethylene (BiFeO3/LDPE) dielectric composites are developed to explore the material processing method to modify the crystalline morphology, magnetic and dielectric properties. The magnetic field treatment can induce the dipole in the LDPE macromolecular chain which leads to preferred orientation of polyethylene crystal grains to the direction of the magnetization field. The surface morphology of the materials measured by atomic force microscope (AFM) implies that the LDPE macromolecular chains in BiFeO3/LDPE composites have been orderly arranged and form thicker lamellae accumulated with a larger spacing after high temperature magnetization, resulting in the increased dimension and orientation of spherulites. The residual magnetization intensities of BiFeO3/LDPE composites have been significantly improved by magnetization treatments at ambient temperature. After this magnetization at ambient temperature, the MR of nano- and micron-BiFeO3/LDPE composites approach to 4.415 × 10−3 and 0.690 × 10−3 emu/g, respectively. The magnetic moments of BiFeO3 fillers are arranged parallel to the magnetic field direction, leading to appreciable enhancement of the magnetic interactions between BiFeO3 fillers, which will inhibit the polarization of the electric dipole moments at the interface between BiFeO3 fillers and the LDPE matrix. Therefore, magnetization treatment results in the lower dielectric constant and higher dielectric loss of BiFeO3/LDPE composites. It is proven that the magnetic and dielectric properties of polymer dielectric composites can be effectively modified by the magnetization treatment in the melt blending process of preparing composites, which is expected to provide a technical strategy for developing magnetic polymer dielectrics.

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“…Therefore, it is reasonable to conjecture that the exothermic nature of crystallization and heat transfer effects might impact polymer nucleation. While there has been much work [7][8][9][10][11][12][13][14][15] probing the molecular-level details of polymer crystallization using simulations, this previous work relied on isothermal simulations, and neglected the role of heat transfer during polymer crystallization.…”

Section: Introductionmentioning

confidence: 99%

Polymer Nucleation under High-Driving Force, Long-Chain Conditions: Heat Release and the Separation of Timescales

Hall¹,

Percec²,

Klein³

2018

Preprint

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<p>This study reveals two important features of polymer crystal formation at high-driving forces in entangled polymer melts based on molecular dynamics simulations of polyethylene, a prototypical polymer. First, in contrast to existing literature on small-molecule crystallization, it is demonstrated that the heat released during polymer crystallization does not appreciably influence molecular-level structural details of early-stage, crystalline clusters (i.e., polymer crystal nuclei). Second, it is revealed that early-stage polymer crystallization (i.e., crystal nucleation) can occur without substantial chain-level relaxation and conformational changes, which is consistent with previous experimental work and yet in contrast to many previous computational studies. Given the conditions used to process polyethylene, the separation of timescales associated with crystallization and chain-level processes is anticipated to be of substantial importance to processing strategies. This study thus provides insights that highlight new research directions for understanding polymer crystallization under industrially-relevant conditions while also providing guidance as to how this work can be undertaken.</p>

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Crystal Growth in Polyethylene by Molecular Dynamics: The Crystal Edge and Lamellar Thickness

Cited by 54 publications

References 67 publications

Monodisperse Polymer Melts Crystallize via Structurally Polydisperse Nanoscale Clusters: Insights from Polyethylene

Monodisperse Polymer Melts Crystallize via Structurally Polydisperse Nanoscale Clusters: Insights from Polyethylene

Magnetic and Dielectric Properties of Nano- and Micron-BiFeO3/LDPE Composites with Magnetization Treatments

Polymer Nucleation under High-Driving Force, Long-Chain Conditions: Heat Release and the Separation of Timescales

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