Polymer Nucleation

and, Kiyoka N. Okada; Hikosaka, Masamichi

doi:10.1002/9781118541838.ch4

Cited by 15 publications

(10 citation statements)

References 58 publications

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“…1C and 2A). Previous computational 28 and experimental 23,24 studies have also claimed that polymer nuclei exhibit rough interfaces.…”

Section: Resultsmentioning

confidence: 91%

“…A detailed description of nucleus shape is needed; many shapes might be seemingly "point-like" depending on the scale of observation. In fact, some studies 23,24 have claimed that polymer nuclei are capable of adopting "all possible shapes" based on results from synchrotron small angle X-ray scattering (SAXS). Computational and theoretical studies similarly provide an unclear perspective on the structure of nascent polymer crystal clusters.…”

Section: Introductionmentioning

confidence: 99%

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Divining the shape of nascent polymer crystal nuclei

Hall

Sirk

Percec

et al. 2019

The Journal of Chemical Physics

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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.

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“…1C and 2A). Previous computational 28 and experimental 23,24 studies have also claimed that polymer nuclei exhibit rough interfaces.…”

Section: Resultsmentioning

confidence: 91%

Section: Introductionmentioning

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

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“…The degree of entanglement is characterized by the entanglement density, which is one of the fundamental characteristics of polymer melts, determining their viscoelastic properties. In solid polymers, the entanglement density influences fracture behavior, the strength of interfacial adhesion in polymer composites, the strain-hardening modulus during plastic deformation, and the resistance to creep failure by slow crack growth in the case of semicrystalline polymers. − Entanglements significantly influence the nucleation rate during crystallization, the size of crystalline and amorphous domains, and long-range order in the adjacent re-entry sequence of chains in the crystal lamellae, whereas this order can hardly be modified by the experimentally accessible crystallization conditions . The entanglement density is also a key parameter when determining the solid-state drawability at elevated temperatures of “soft” semicrystalline polymers that exhibit main chain dynamics in the crystalline phase .…”

Section: Introductionmentioning

confidence: 99%

Melting-Induced Evolution of Morphology, Entanglement Density, and Ultradrawability of Solution-Crystallized Ultrahigh-Molecular-Weight Polyethylene

et al. 2021

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The melting-induced change in density of physical network junctions, which are formed by chain entanglements and network junctions due to anchoring of chain segments to crystals, is studied by 1 H NMR T 2 relaxometry for solution-and melt-crystallized ultra-high molecular weight polyethylene (UHMWPE) -sc-UH and mc-UH, respectively. The NMR results are complemented by real-time synchrotron WAXS and SAXS analyses to extract the sizes of the crystalline lamellae and inter-crystalline domains. Below the melting temperature, the network of physical junctions is denser in the amorphous phase of mc-UH than the one in sc-UH owing to lower entanglement density and smaller number of physical junctions from polymer crystals in sc-UH. However, the difference in the total density of physical junctions between mc-UH and sc-UH films decreases with decreasing crystallinity during melting. At the end of the melting trajectory, at vanishing crystallinity, the volume-average entanglement density, as characterized by the NMR method, is approximately the same in sc-and mc-UH. This indicates that the entanglement density in sc-UH films increases during melting owing to fast buildup of local chain entanglements. These entanglements are formed by segments of the same chain, neighboring chains, or the both due to a displacement of chain fragments upon lamellar thickening and due to the so-" p " that occurs locally in the amorphous domains. The increase in the entanglement density in sc-UH is additionally confirmed by solid-state drawability of sc-UH films that were annealed in the melting region but below the end of melting. The maximum draw ratio decreases and the drawing stress increases with increasing annealing temperature.

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“…Rather than comprising a single uniform phase, semicrystalline polymers are characterized by folded-chain lamellar crystals with intercalated entanglements that remain amorphous. − The structure within semicrystalline polymers has a strong influence on thermal stability, i.e., the melting temperature ( T m ) as well as the mechanical − and electrical ,− properties of semicrystalline polymers. The precise control of structure and T m in polymer thin films, without the need for chemical modification ,− or the inclusion of functional additives, , remains of interest and a formidable challenge in material science.…”

Section: Introductionmentioning

confidence: 99%

Tuning Morphology and Melting Temperature in Polyethylene Films by MAPLE

et al. 2018

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The control of structure and thermal stability in semicrystalline polymer films remains an important challenge in applications ranging from solar energy devices to packaging films. Here, we demonstrate the ability to dramatically alter the morphology and melting temperature (T m ) of low-molecularweight linear polyethylene (PE) by employing an innovative vapor-assisted deposition process termed matrix assisted pulsed laser evaporation (MAPLE). We report the ability to tune T m of PE films by 20 °C by simply adjusting the deposition temperature during MAPLE processing. This unique capability stems from the ability of MAPLE to exploit confined crystallization during thin film growth. In addition, we demonstrate the ability to exploit MAPLE to design PE films that exhibit the same T m as their melt-crystallized analogues but have an ∼25% higher degree of crystallinity. Our investigation offers new insights into how confinement effects in polymer crystallization can be utilized in the emerging field of polymer film fabrication by MAPLE to control structure and key material properties of semicrystalline polymer films.

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Polymer Nucleation

Cited by 15 publications

References 58 publications

Divining the shape of nascent polymer crystal nuclei

Divining the shape of nascent polymer crystal nuclei

Melting-Induced Evolution of Morphology, Entanglement Density, and Ultradrawability of Solution-Crystallized Ultrahigh-Molecular-Weight Polyethylene

Tuning Morphology and Melting Temperature in Polyethylene Films by MAPLE

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