1
|
Wang L, Kusalik PG. Understanding why constant energy or constant temperature may affect nucleation behavior in MD simulations: A study of gas hydrate nucleation. J Chem Phys 2023; 159:184501. [PMID: 37947514 DOI: 10.1063/5.0169669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 10/18/2023] [Indexed: 11/12/2023] Open
Abstract
Molecular dynamics simulations have been widely used in exploring the nucleation behavior of many systems, including gas hydrates. Gas hydrates are ice-like solids in which gas molecules are trapped in water cages. During hydrate formation, a considerable amount of heat is released, and previous work has reported that the choice of temperature control scheme may affect the behavior of hydrate formation. The origins of this effect have remained an open question. To address this question, extensive NVE simulations and thermostatted (NPT and NVT) simulations with different temperature coupling strengths have been performed and compared for systems where a water nanodroplet is immersed in a H2S liquid. Detailed analysis of the hydrate structures and their mechanisms of formation has been carried out. Slower nucleation rates in NVE simulations in comparison to NPT simulations have been observed in agreement with previous studies. Probability distributions for various temperature measures along with their spatial distributions have been examined. Interestingly, a comparison of these temperature distributions reveals a small yet noticeable difference in the widths of the distributions for water. The somewhat reduced fluctuations in the temperature for the water species in the NVE simulations appear to be responsible for reducing the hydrate nucleation rate. We further conjecture that the NVE-impeded nucleation rate may be the result of the finite size of the surroundings (here the liquid H2S portion of the system). Additionally, a local spatial temperature gradient arising from the heat released during hydrate formation could not be detected.
Collapse
Affiliation(s)
- Lei Wang
- Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Peter G Kusalik
- Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| |
Collapse
|
2
|
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.
Collapse
Affiliation(s)
- Takashi Yamamoto
- Department of Physics and Informatics, Yamaguchi University, Japan
| |
Collapse
|
3
|
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
| |
Collapse
|
4
|
Leyva-Porras C, Balderrama-Aguilar A, Estrada-Ávila Y, Espelosín-Gómez I, Mendoza-Duarte M, Piñón-Balderrama C, Saavedra-Leos MZ, Estrada-Moreno I. Injection Molding of Low-Density Polyethylene (LDPE) as a Model Polymer: Effect of Molding Parameters on the Microstructure and Crystallinity. Polymers (Basel) 2021; 13:3597. [PMID: 34685356 PMCID: PMC8538698 DOI: 10.3390/polym13203597] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/07/2021] [Accepted: 10/13/2021] [Indexed: 02/01/2023] Open
Abstract
Due to its relatively simple structure, low-density polyethylene (LDPE) can be considered as a model polymer for the study of its properties. Herein, the effect of processing variables on the microstructure and crystallinity of injection-molded LDPE specimens was quantitatively determined. The polymer was injected at different temperature conditions in the barrel and the mold. The specimens were characterized by scanning electron microscopy and X-ray diffraction. With the data obtained, an analysis of variance (ANOVA) was carried out, and response surface graphs (SRP) were constructed to quantify and to observe the behavior of the processing variables, respectively. Different models were obtained to predict the effect of the experimental factors on the response variables. The results showed that the interaction of the two temperatures has the greatest effect on the size of the spherulite, while the temperature of the mold affects the crystallinity. The SRP showed different behaviors: for the spherulite, the size increases with the mold temperature, while for the crystallinity, higher values were observed at an intermediate mold temperature and a low melt temperature. The results presented herein are valuable for setting empirical relations between the microstructure, crystallinity, and the molding conditions of LDPE.
Collapse
Affiliation(s)
- César Leyva-Porras
- Centro de Investigación en Materiales Avanzados S.C. (CIMAV), Complejo Industrial Chihuahua, Miguel de Cervantes No. 120, Chihuahua 31136, Mexico;
| | - Andrea Balderrama-Aguilar
- Tecnológico Nacional de México, Campus Chihuahua (ITCH), Av. Tecnológico No. 2009, Chihuahua 31310, Mexico; (A.B.-A.); (Y.E.-Á.); (I.E.-G.)
| | - Yael Estrada-Ávila
- Tecnológico Nacional de México, Campus Chihuahua (ITCH), Av. Tecnológico No. 2009, Chihuahua 31310, Mexico; (A.B.-A.); (Y.E.-Á.); (I.E.-G.)
| | - Iñaki Espelosín-Gómez
- Tecnológico Nacional de México, Campus Chihuahua (ITCH), Av. Tecnológico No. 2009, Chihuahua 31310, Mexico; (A.B.-A.); (Y.E.-Á.); (I.E.-G.)
| | - Mónica Mendoza-Duarte
- Centro de Investigación en Materiales Avanzados S.C. (CIMAV), Complejo Industrial Chihuahua, Miguel de Cervantes No. 120, Chihuahua 31136, Mexico;
| | - Claudia Piñón-Balderrama
- Departamento de Ingeniería Industrial, Universidad Tecnológica de Chihuahua (UTCH), Montes Americanos No. 9501, Chihuahua 31216, Mexico;
| | - María Zenaida Saavedra-Leos
- Coordinación Académica Región Altiplano, Universidad Autónoma de San Luis Potosí, Carretera Cedral Km. 5+600 Ejido San José de las Trojes, Matehuala 78700, San Luis Potosí, Mexico;
| | - Iván Estrada-Moreno
- Centro de Investigación en Materiales Avanzados S.C. (CIMAV), Complejo Industrial Chihuahua, Miguel de Cervantes No. 120, Chihuahua 31136, Mexico;
| |
Collapse
|
5
|
Yagasaki T, Matubayasi N. Crystallization of Polyethylene Brushes and Its Effect on Interactions with Water. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c01145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Takuma Yagasaki
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan
| | - Nobuyuki Matubayasi
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan
| |
Collapse
|
6
|
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.
Collapse
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.
| |
Collapse
|
7
|
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
| |
Collapse
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
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.
Collapse
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;
| |
Collapse
|
10
|
Hall KW, Sirk TW, Percec S, Klein ML, Shinoda W. Divining the shape of nascent polymer crystal nuclei. J Chem Phys 2019; 151:144901. [PMID: 31615257 DOI: 10.1063/1.5123983] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
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, postcritical 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.
Collapse
Affiliation(s)
- Kyle Wm Hall
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - Timothy W Sirk
- U.S. Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, Maryland 21005, USA
| | - Simona Percec
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - Michael L Klein
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - Wataru Shinoda
- Department of Materials Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| |
Collapse
|
11
|
Hall KW, Sirk TW, Klein ML, Shinoda W. A coarse-grain model for entangled polyethylene melts and polyethylene crystallization. J Chem Phys 2019; 150:244901. [PMID: 31255065 DOI: 10.1063/1.5092229] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The Shinoda-DeVane-Klein (SDK) model is herein demonstrated to be a viable coarse-grain model for performing molecular simulations of polyethylene (PE), affording new opportunities to advance molecular-level, scientific understanding of PE materials and processes. Both structural and dynamical properties of entangled PE melts are captured by the SDK model, which also recovers important aspects of PE crystallization phenomenology. Importantly, the SDK model can be used to represent a variety of materials beyond PE and has a simple functional form, making it unique among coarse-grain PE models. This study expands the suite of tools for studying PE in silico and paves the way for future work probing PE and PE-based composites at the molecular level.
Collapse
Affiliation(s)
- Kyle Wm Hall
- Department of Materials Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Timothy W Sirk
- U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005, USA
| | - Michael L Klein
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - Wataru Shinoda
- Department of Materials Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| |
Collapse
|