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Smith ER, Theodorakis PE. Multiscale simulation of fluids: coupling molecular and continuum. Phys Chem Chem Phys 2024; 26:724-744. [PMID: 38113114 DOI: 10.1039/d3cp03579d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
Computer simulation is an important tool for scientific progress, especially when lab experiments are either extremely costly and difficult or lack the required resolution. However, all of the simulation methods come with limitations. In molecular dynamics (MD) simulation, the length and time scales that can be captured are limited, while computational fluid dynamics (CFD) methods are built on a range of assumptions, from the continuum hypothesis itself, to a variety of closure assumptions. To address these issues, the coupling of different methodologies provides a way to retain the best of both methods. Here, we provide a perspective on multiscale simulation based on the coupling of MD and CFD with each a distinct part of the same simulation domain. This style of coupling allows molecular detail to be present only where it is needed, so CFD can model larger scales than possible with MD alone. We present a unified perspective of the literature, showing the links between the two main types of coupling, state and flux, and discuss the varying assumptions in their use. A unique challenge in such coupled simulation is obtaining averages and constraining local parts of a molecular simulation. We highlight that incorrect localisation has resulted in an error in the literature. We then finish with some applications, focused on the simulation of fluids. Thus, we hope to motivate further research in this exciting area with applications across the spectrum of scientific disciplines.
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Affiliation(s)
- Edward R Smith
- Department of Mechanical and Aerospace Engineering, Brunel University London, Uxbridge, Middlesex UB8 3PH, UK.
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Fluoropolymer: A Review on Its Emulsion Preparation and Wettability to Solid-Liquid Interface. MOLECULES (BASEL, SWITZERLAND) 2023; 28:molecules28020905. [PMID: 36677962 PMCID: PMC9866989 DOI: 10.3390/molecules28020905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 12/13/2022] [Accepted: 12/14/2022] [Indexed: 01/18/2023]
Abstract
In the preparation of a superamphiphobic surface, the most basic method is to reduce the surface free energy of the interface. The C-F bond has a very low surface free energy, which can significantly change the wettability of the solid-liquid interface and make it a hydrophobic or oleophobic, or even superamphiphobic surface. Based on the analysis of a large number of research articles, the preparation and application progress in fluoropolymer emulsion were summarized. After that, some corresponding thoughts were put forward combined with our professional characteristics. According to recent research, the status of the fluoropolymer emulsion preparation system was analyzed. In addition, all related aspects of fluoropolymer emulsion were systematically classified in varying degrees. Furthermore, the interaction between fluoropolymer structure and properties, especially the interaction with nanomaterials, was also explored. The aim of this review is to try to attract more scholars' attention to fluorocarbon interfacial materials. It is expected that it will make a certain theoretical and practical significance in the preparation and application of fluoropolymer.
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Interfacial Forces in Free-Standing Layers of Melted Polyethylene, from Critical to Nanoscopic Thicknesses. Polymers (Basel) 2022; 14:polym14183865. [PMID: 36146008 PMCID: PMC9503058 DOI: 10.3390/polym14183865] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/04/2022] [Accepted: 09/07/2022] [Indexed: 11/17/2022] Open
Abstract
Molecular dynamics simulations of ultrathin free-standing layers made of melted (373.15–673.15 K) polyethylene chains, which exhibit a lower melting temperature (compared to the bulk value), were carried out to investigate the dominant pressure forces that shape the conformation of chains at the interfacial and bulk liquid regions. We investigated layer thicknesses, tL, from the critical limit of mechanical stability up to lengths of tens of nm and found a normal distribution of bonds dominated by slightly stretched chains across the entire layer, even at large temperatures. In the bulk region, the contribution of bond vibrations to pressure was one order of magnitude larger than the contributions from interchain interactions, which changed from cohesive to noncohesive at larger temperatures just at a transition temperature that was found to be close to the experimentally derived onset temperature for thermal stability. The interchain interactions produced noncohesive interfacial regions at all temperatures in both directions (normal and lateral to the surface layer). Predictions for the value of the surface tension, γ, were consistent with experimental results and were independent of tL. However, the real interfacial thickness—measured from the outermost part of the interface up to the point where γ reached its maximum value—was found to be dependent on tL, located at a distance of 62 Å from the Gibbs dividing surface in the largest layer studied (1568 chains or 313,600 bins); this was ~4 times the length of the interfacial thickness measured in the density profiles.
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Choi JH, Kwon T, Sung BJ. Relative Chain Flexibility Determines the Spatial Arrangement and the Diffusion of a Single Ring Chain in Linear Chain Films. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c01937] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Jong Ho Choi
- Department of Chemistry, Sogang University, Seoul 04107, Republic of Korea
| | - Taejin Kwon
- Department of Chemistry, Sogang University, Seoul 04107, Republic of Korea
| | - Bong June Sung
- Department of Chemistry, Sogang University, Seoul 04107, Republic of Korea
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Zhang F, He Q, Zhou Y, Narayanan S, Wang C, Vogt BD, Foster MD. Anomalous Confinement Slows Surface Fluctuations of Star Polymer Melt Films. ACS Macro Lett 2018; 7:834-839. [PMID: 35650756 DOI: 10.1021/acsmacrolett.8b00278] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The unusually large film thickness at which confinement effects manifest themselves in surface fluctuations of unentangled four-arm star polymers has been defined using film thicknesses from 10Rg to 107Rg. For 15k four-arm star polystyrene (SPS), confinement appears at a thickness between 112 nm (40Rg) and 72 nm (26Rg), which is remarkably larger than the thicknesses at which confinement appears for unentangled 6k linear (<15 nm, <7Rg) and 6k and 14k cyclic (24 and 22 nm, respectively) polystyrenes. Data for 15k star films can be rationalized using a two-layer model with a 17 nm (6Rg) thick highly viscous layer at the substrate, which is significantly thicker than the 1Rg thick "irreversibly adsorbed" layer. For a 29 nm (10Rg) thick film, more striking confinement occurs due to the combined influence of both interfaces. These results underscore the extraordinary role long-chain branching plays in dictating surface fluctuations of thin films.
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Affiliation(s)
| | | | | | - Suresh Narayanan
- X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
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Gaitho FM, Tsige M, Mola GT, Pellicane G. Surface Segregation of Cyclic Chains in Binary Melts of Thin Polymer Films: The Influence of Constituent Concentration. Polymers (Basel) 2018; 10:E324. [PMID: 30966359 PMCID: PMC6414847 DOI: 10.3390/polym10030324] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 02/21/2018] [Accepted: 03/02/2018] [Indexed: 12/30/2022] Open
Abstract
We carry out extensive molecular dynamics simulations of thin films of bead-spring models of binary mixtures composed of cyclic and linear polymer chains. We study the equilibrium behavior of the polymer chains for two very different chain lengths, which resemble short (10-mers) and long (100-mers) chains, at different concentrations of the binary mixture. We clearly show how the concentration variable affects the enrichment of either of the two polymer species at the interface, and also how the chain length influences this process.
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Affiliation(s)
- Francis M Gaitho
- School of Chemistry & Physics, University of KwaZulu-Natal, Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa.
| | - Mesfin Tsige
- Department of Polymer Science, University of Akron, Akron, OH 44325, USA.
| | - Genene T Mola
- School of Chemistry & Physics, University of KwaZulu-Natal, Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa.
| | - Giuseppe Pellicane
- School of Chemistry & Physics, University of KwaZulu-Natal, Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa.
- National Institute of Theoretical Physics (NITheP) KZN Node, Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa.
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Gaitho FM, Mola GT, Pellicane G. Computational approach to the study of morphological properties of polymer/fullerene blends in photovoltaics. PHYSICAL SCIENCES REVIEWS 2018. [DOI: 10.1515/psr-2017-0102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Organic solar cells have the ability to transform solar energy efficiently and have a promising energy balance. Producing these cells is economical and makes use of methods of printing using inks built on solvents that are well-matched with a variety of cheap materials like flexible plastic or paper. The primary materials used to manufacture organic solar cells include carbon-based semiconductors, which are good light absorbers and efficient charge generators. In this article, we review previous research of interest based on morphology of polymer blends used in bulk heterojunction (BHJ) solar cells and introduce their basic principles. We further review computational models used in the analysis of surface behavior of polymer blends in BHJ as well as the trends in the field of polymer surface science as applied to BHJ photovoltaics. We also give in brief, the opportunities and challenges in the area of polymer blends on BHJ organic solar cells.
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Affiliation(s)
- Francis M. Gaitho
- School of Chemistry and Physics , University of KwaZulu-Natal, Pietermaritzburg campus , Private Bag X01 , Scottsville 3209 , South Africa
| | - Genene T. Mola
- School of Chemistry and Physics , University of KwaZulu-Natal, Pietermaritzburg campus , Private Bag X01 , Scottsville 3209 , South Africa
| | - Giuseppe Pellicane
- School of Chemistry and Physics , University of KwaZulu-Natal, Pietermaritzburg campus , Private Bag X01 , Scottsville 3209 , South Africa
- National Institute of Theoretical Physics (NITheP) KZN node , Pietermaritzburg , South Africa
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Gartner TE, Jayaraman A. Macromolecular 'size' and 'hardness' drives structure in solvent-swollen blends of linear, cyclic, and star polymers. SOFT MATTER 2018; 14:411-423. [PMID: 29251311 DOI: 10.1039/c7sm02199b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this paper, we apply molecular simulation and liquid state theory to uncover the structure and thermodynamics of homopolymer blends of the same chemistry and varying chain architecture in the presence of explicit solvent species. We use hybrid Monte Carlo (MC)/molecular dynamics (MD) simulations in the Gibbs ensemble to study the swelling of ∼12 000 g mol-1 linear, cyclic, and 4-arm star polystyrene chains in toluene. Our simulations show that the macroscopic swelling response is indistinguishable between the various architectures and matches published experimental data for the solvent annealing of linear polystyrene by toluene vapor. We then use standard MD simulations in the NPT ensemble along with polymer reference interaction site model (PRISM) theory to calculate effective polymer-solvent and polymer-polymer Flory-Huggins interaction parameters (χeff) in these systems. As seen in the macroscopic swelling results, there are no significant differences in the polymer-solvent and polymer-polymer χeff between the various architectures. Despite similar macroscopic swelling and effective interaction parameters between various architectures, the pair correlation function between chain centers-of-mass indicates stronger correlations between cyclic or star chains in the linear-cyclic blends and linear-star blends, compared to linear chain-linear chain correlations. Furthermore, we note striking similarities in the chain-level correlations and the radius of gyration of cyclic and 4-arm star architectures of identical molecular weight. Our results indicate that the cyclic and star chains are 'smaller' and 'harder' than their linear counterparts, and through comparison with MD simulations of blends of soft spheres with varying hardness and size we suggest that these macromolecular characteristics are the source of the stronger cyclic-cyclic and star-star correlations.
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Affiliation(s)
- Thomas E Gartner
- Department of Chemical and Biomolecular Engineering, Colburn Laboratory, University of Delaware, 150 Academy Street, Newark, DE 19716, USA
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He Q, Wang SF, Hu R, Akgun B, Tormey C, Peri S, Wu DT, Foster MD. Evidence and Limits of Universal Topological Surface Segregation of Cyclic Polymers. PHYSICAL REVIEW LETTERS 2017; 118:167801. [PMID: 28474912 DOI: 10.1103/physrevlett.118.167801] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Indexed: 06/07/2023]
Abstract
If you mix lines and circles, what happens at the edge of the mixture? The problem is simply stated, but the answer is not obvious. Twenty years ago it was proposed that a universal topological driving force would drive cyclic chains to enrich the surface of blends of linear and cyclic chains. Here such behavior is demonstrated experimentally for sufficiently long chains and the limit in molecular weight where packing effects dominate over the topological driving force is identified.
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Affiliation(s)
- Qiming He
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, USA
| | - Shih-Fan Wang
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, USA
| | - Renfeng Hu
- Chemical Engineering and Chemistry Departments, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Bulent Akgun
- Department of Chemistry, Bogazici University, Bebek, Istanbul 34342, Turkey
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland, 20742, USA
| | - Caleb Tormey
- Chemical Engineering and Chemistry Departments, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Somesh Peri
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, USA
| | - David T Wu
- Chemical Engineering and Chemistry Departments, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Mark D Foster
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, USA
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