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Hagita K, Yamamoto T, Saito H, Abe E. Chain-Level Analysis of Reinforced Polyethylene through Stretch-Induced Crystallization. ACS Macro Lett 2024:247-251. [PMID: 38329290 PMCID: PMC10883302 DOI: 10.1021/acsmacrolett.3c00554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Herein, we propose a large-scale simulation approach to perform the stretch-induced crystallization of entangled polyethylene (PE) melts. Sufficiently long (1000 ns) united-atom molecular dynamics (UAMD) simulations for 16000 chains of 1000 consecutive CH2 united-atom particles under periodic boundary conditions were performed to achieve the crystallinity observed in experiments. Before the isothermal crystallization process, we applied uniaxial stretching as pre-elongation to the embedded strain memory on the entangled PE melts. We confirmed significant differences in the morphologies of crystal domains and scattering patterns for pre-elongation ratios of 400% and 800%. The obtained scattering patterns were consistent with the experimental results. Uniaxial stretching MD simulations revealed that the elastic modulus at 800% pre-elongation was stronger than that at 400% pre-elongation. From this observation, we can derive the structure-property relationship, wherein the magnitude of the pre-elongation governs the crystal domain structures and mechanical properties.
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Affiliation(s)
- Katsumi Hagita
- Department of Applied Physics, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka 239-8686, Japan
| | - Takashi Yamamoto
- Graduate School of Science and Engineering, Yamaguchi University, Yamaguchi 753-8512, Japan
| | - Hiromu Saito
- Department of Organic and Polymer Materials Chemistry, Tokyo University of Agriculture and Technology, Koganei 184-8588, Japan
| | - Eiji Abe
- Department of Materials Science and Engineering, University of Tokyo, Tokyo 113-8656, Japan
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2
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Yamamoto T. Chiral selecting crystallization of helical polymers: A molecular dynamics simulation for the POM-like bare helix. J Chem Phys 2022; 157:014901. [DOI: 10.1063/5.0097112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Polymer crystallization has long been a fascinating problem and is still attracting many researchers. Most of the previous simulations are concentrated on clarifying the universal aspects of polymer crystallization using model linear polymers such as polyethylene. We are recently focusing on a nearly untouched but very interesting problem of chiral selecting crystallization in helical polymers. We previously proposed a stepwise approach using two kinds of helical polymers, simple "bare" helical polymers made of backbone atoms only such as polyoxymethylene (POM) and "general" helical polymers containing complicated side groups such as isotactic polypropylene (iPP). We have already reported on the crystallization in oligomeric POM-like helix but have observed only weak chiral selectivity during crystallization. In the present paper, we investigate the crystallization of sufficiently long POM-like polymer both from the isotropic melt and from the highly stretched melt. We find in both cases that the polymer shows a clear chiral selecting crystallization. Especially the observation of a single crystal growing from the isotropic melt is very illuminating. It shows that the crystal thickness and the crystal chirality is closely correlated; thicker crystals show definite chirality while thinner ones are mostly mixtures of the R- and the L- handed stems. The single crystal is found to have a marked lenticular shape, where the thinner growth front, since being made of the mixture, shows no chiral selectivity. Final chiral crystal is found to be completed through helix reversal processes within thicker regions.
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Affiliation(s)
- Takashi Yamamoto
- Department of Physics and Informatics, Yamaguchi University, Japan
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3
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Kawak P, Banks DS, Tree DR. Semiflexible oligomers crystallize via a cooperative phase transition. J Chem Phys 2021; 155:214902. [PMID: 34879681 DOI: 10.1063/5.0067788] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Semicrystalline polymers are ubiquitous, yet despite their fundamental and industrial importance, the theory of homogeneous nucleation from a melt remains a subject of debate. A key component of the controversy is that polymer crystallization is a non-equilibrium process, making it difficult to distinguish between effects that are purely kinetic and those that arise from the underlying thermodynamics. Due to computational cost constraints, simulations of polymer crystallization typically employ non-equilibrium molecular dynamics techniques with large degrees of undercooling that further exacerbate the coupling between thermodynamics and kinetics. In a departure from this approach, in this study, we isolate the near-equilibrium nucleation behavior of a simple model of a melt of short, semiflexible oligomers. We employ several Monte Carlo methods and compute a phase diagram in the temperature-density plane along with two-dimensional free energy landscapes (FELs) that characterize the nucleation behavior. The phase diagram shows the existence of ordered nematic and crystalline phases in addition to the disordered melt phase. The minimum free energy path in the FEL for the melt-crystal transition shows a cooperative transition, where nematic order and monomer positional order move in tandem as the system crystallizes. This near-equilibrium phase transition mechanism broadly agrees with recent evidence that polymer stiffness plays an important role in crystallization but differs in the specifics of the mechanism from several recent theories. We conclude that the computation of multidimensional FELs for models that are larger and more fine-grained will be important for evaluating and refining theories of homogeneous nucleation for polymer crystallization.
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Affiliation(s)
- Pierre Kawak
- Department of Chemical Engineering, Brigham Young University, Provo, Utah 84602, USA
| | - Dakota S Banks
- Department of Chemical Engineering, Brigham Young University, Provo, Utah 84602, USA
| | - Douglas R Tree
- Department of Chemical Engineering, Brigham Young University, Provo, Utah 84602, USA
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4
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Zhang R, Fall WS, Hall KW, Gehring GA, Zeng X, Ungar G. Roughening Transition and Quasi-continuous Melting of Monolayers of Ultra-long Alkanes: Why Bulk Polymer Melting Is Strongly First-Order. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c01377] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ruibin Zhang
- Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, UK
- State Key Laboratory for Mechanical Behavior of Materials, Shaanxi International Research Centre for Soft Materials, Xi’an Jiaotong University, Xi’an 710049, China
- Department of Physics, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - William S. Fall
- State Key Laboratory for Mechanical Behavior of Materials, Shaanxi International Research Centre for Soft Materials, Xi’an Jiaotong University, Xi’an 710049, China
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
- Institut Charles Sadron, Université de Strasbourg, CNRS, UPR 22, 67034 Strasbourg, France
| | - Kyle Wm. Hall
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Gillian A. Gehring
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
| | - Xiangbing Zeng
- Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, UK
| | - Goran Ungar
- Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, UK
- State Key Laboratory for Mechanical Behavior of Materials, Shaanxi International Research Centre for Soft Materials, Xi’an Jiaotong University, Xi’an 710049, China
- Department of Physics, Zhejiang Sci-Tech University, Hangzhou 310018, China
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5
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Anwar M, Graham RS. Direct observation of long chain enrichment in flow-induced nuclei from molecular dynamics simulations of bimodal blends. SOFT MATTER 2021; 17:2872-2882. [PMID: 33586745 DOI: 10.1039/d0sm01361g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Modelling of flow-induced nucleation in polymers suggest that long chains are enriched in nuclei, relative to their melt concentration. This enrichment has important consequences for the nucleation rate and mechanism, but cannot be directly observed with current experimental techniques. Instead, we ran united atom molecular dynamics simulations of bimodal polyethylene blends, comprising linear chains at a 50 : 50 mix of long (1000 carbon) and short (500-125 carbon) chains, under shear flow. We developed a method to extract the nucleus composition during a transient start-up flow. Our simulations show significant and systematic enrichment of long-chains for all nucleus sizes up to and beyond the critical nucleus. This enrichment is quantitatively predicted by the recent polySTRAND model [Read et al. Phys. Rev. Lett. 2020, 124, 147802]. The same model parameters also correctly capture the nucleus induction time in our simulations. All parameters of the model were fitted to a small subset of our data in which long chain enhancement was absent. We conclude that long-chain enrichment is central to the mechanism of flow-induced nucleation and that this enrichment must be captured to correctly predict the nucleation rate.
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Affiliation(s)
- Muhammad Anwar
- School of Mathematical Sciences, University of Nottingham, Nottingham, NG9 4DP, UK.
| | - Richard S Graham
- School of Mathematical Sciences, University of Nottingham, Nottingham, NG9 4DP, UK.
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6
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Zhang R, Fall WS, Hall KW, Gehring GA, Zeng X, Ungar G. Quasi-continuous melting of model polymer monolayers prompts reinterpretation of polymer melting. Nat Commun 2021; 12:1710. [PMID: 33731691 PMCID: PMC7969604 DOI: 10.1038/s41467-021-21799-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 02/09/2021] [Indexed: 11/10/2022] Open
Abstract
Condensed matter textbooks teach us that melting cannot be continuous and indeed experience, including with polymers and other long-chain compounds, tells us that it is a strongly first-order transition. However, here we report nearly continuous melting of monolayers of ultralong n-alkane C390H782 on graphite, observed by AFM and reproduced by mean-field theory and MD simulation. On heating, the crystal-melt interface moves steadily and reversibly from chain ends inward. Remarkably, the final melting point is 80 K above that of the bulk, and equilibrium crystallinity decreases continuously from ~100% to <50% prior to final melting. We show that the similarity in melting behavior of polymers and non-polymers is coincidental. In the bulk, the intermediate melting stages of long-chain crystals are forbidden by steric overcrowding at the crystal-liquid interface. However, there is no crowding in a monolayer as chain segments can escape to the third dimension.
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Affiliation(s)
- Ruibin Zhang
- State Key Laboratory for Mechanical Behavior of Materials, Shaanxi International Research Centre for Soft Materials, Xi'an Jiaotong University, Xi'an, China.,Department of Materials Science and Engineering, University of Sheffield, Sheffield, UK.,Department of Physics, Zhejiang Sci-Tech University, Hangzhou, China
| | - William S Fall
- State Key Laboratory for Mechanical Behavior of Materials, Shaanxi International Research Centre for Soft Materials, Xi'an Jiaotong University, Xi'an, China.,Department of Physics and Astronomy, University of Sheffield, Sheffield, UK
| | - Kyle Wm Hall
- Department of Chemistry, Temple University, Philadelphia, PA, USA
| | - Gillian A Gehring
- Department of Physics and Astronomy, University of Sheffield, Sheffield, UK
| | - Xiangbing Zeng
- Department of Materials Science and Engineering, University of Sheffield, Sheffield, UK.
| | - Goran Ungar
- State Key Laboratory for Mechanical Behavior of Materials, Shaanxi International Research Centre for Soft Materials, Xi'an Jiaotong University, Xi'an, China. .,Department of Physics, Zhejiang Sci-Tech University, Hangzhou, China.
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7
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Hall KW, Percec S, Shinoda W, Klein ML. Chain-End Modification: A Starting Point for Controlling Polymer Crystal Nucleation. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02398] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Kyle Wm. Hall
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
- Institute for Computational Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Simona Percec
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Wataru Shinoda
- Department of Materials Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Michael L. Klein
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
- Institute for Computational Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States
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8
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Hall KW, Percec S, Shinoda W, Klein ML. Property Decoupling across the Embryonic Nucleus-Melt Interface during Polymer Crystal Nucleation. J Phys Chem B 2020; 124:4793-4804. [PMID: 32413263 DOI: 10.1021/acs.jpcb.0c01972] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Spatial distributions are presented that quantitatively capture how polymer properties (e.g., segment alignment, density, and potential energy) vary with distance from nascent polymer crystals (nuclei) in prototypical polyethylene melts. It is revealed that the spatial extent of nuclei and their interfaces is metric-dependent as is the extent to which nucleus interiors are solid-like. As distance from a nucleus increases, some properties, such as density, decay to melt-like behavior more rapidly than polymer segment alignment, indicating that a polymer nucleus resides in a nematic-like droplet. This nematic-like droplet region coincides with enhanced formation of ordered polymer segments that are not part of the nucleus. It is more favorable to find nonconstituent ordered polymer segments near a nucleus than in the surrounding metastable melt, pointing to the possibility of one nucleus inducing the formation of other nuclei. In this vein, there is also a second region of enhanced ordering that lies along the nematic director of a nucleus, but beyond its nematic droplet and fold regions. These results indicate that crystal stacking, a key characteristic of lamellae in semicrystalline polymeric materials, begins to emerge during the earliest stages of polymer crystallization (i.e., crystal nucleation). More generally, the findings of this study provide a conceptual bridge between polymer crystal nucleation under nonflow and flow conditions and are used to rationalize previous results.
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Affiliation(s)
- Kyle Wm Hall
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States.,Institute for Computational Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Simona Percec
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Wataru Shinoda
- Department of Materials Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Michael L Klein
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States.,Institute for Computational Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States
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Hall KW, Sirk TW, Percec S, Klein ML, Shinoda W. Monodisperse Polymer Melts Crystallize via Structurally Polydisperse Nanoscale Clusters: Insights from Polyethylene. Polymers (Basel) 2020; 12:E447. [PMID: 32074962 PMCID: PMC7077701 DOI: 10.3390/polym12020447] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 02/06/2020] [Accepted: 02/07/2020] [Indexed: 11/21/2022] Open
Abstract
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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Affiliation(s)
- Kyle Wm. Hall
- Department of Chemistry, Temple University, Philadelphia, PA 19122, USA; (S.P.); (M.L.K.)
- Institute for Computational Molecular Science, Temple University, Philadelphia, PA 19122, USA
| | - Timothy W. Sirk
- U.S. Army Research Laboratory, Aberdeen Proving Ground, MD 21005, USA;
| | - Simona Percec
- Department of Chemistry, Temple University, Philadelphia, PA 19122, USA; (S.P.); (M.L.K.)
| | - Michael L. Klein
- Department of Chemistry, Temple University, Philadelphia, PA 19122, USA; (S.P.); (M.L.K.)
- Institute for Computational Molecular Science, Temple University, Philadelphia, PA 19122, USA
| | - Wataru Shinoda
- Department of Materials Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan;
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