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Polymers
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Molecular Dynamics Simulation of Polymer for Absorption and Separation Applications
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Molecular Dynamics Simulation of Polymer for Absorption and Separation Applications

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Physics and Theory".

Deadline for manuscript submissions: closed (15 January 2024) | Viewed by 5838

Special Issue Editors

Dr. Ioannis Tanis

E-Mail Website
Guest Editor
The Cyprus Institute, Aglantzia, Cyprus
Interests: atomistic simulation; Monte Carlo methods; coarse-graining; polymer membranes; gas separation; thin films; drug delivery; polymer nanocomposites
Prof. Dr. Costas H. Vlahos

E-Mail Website
Guest Editor
Department of Chemistry, University of Ioannina, Ioannina, Greece
Interests: simulations; micelles; brushes; polyelectrolytes
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Adsorption and separation are highly efficient processes that are widely used in diverse applications ranging from wastewater treatment, desalination, and forward and reverse osmosis to natural gas purification and hydrogen  storage. Polymer membranes and nanocomposites are a class of materials that are appealing candidates in the aforementioned applications due to their unique attributes, such as the existence of easily modifiable functional groups, as well as their high thermal and mechanical stability. Molecular dynamics simulations constitute an invaluable tool for the study of such processes as they can successfully complement experimental approaches and shed light on mechanism operations at the molecular level, such as polymer–penetrant interactions and penetrant transport in the polymer matrix micro-cavities. On these grounds, this Special Issue invites the submission of manuscripts which present recent developments in this field, through the use of various computational methods, such as equilibrium and non-equilibrium molecular dynamics, (kinetic) Monte Carlo, as well as multiscale techniques. Contributions which present complementary experimental and numerical approaches are particularly welcome.

Dr. Ioannis Tanis
Prof. Dr. Costas H. Vlahos
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • molecular dynamics
  • Monte Carlo
  • diffusion
  • permeability
  • separation factor
  • solubility
  • adsorption
  • polymer membranes
  • polymer nanocomposites

Published Papers (5 papers)

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Research

22 pages, 5154 KiB  
Article
Connecting Structural Characteristics and Material Properties in Phase-Separating Polymer Solutions: Phase-Field Modeling and Physics-Informed Neural Networks
by Le-Chi Lin, Sheng-Jer Chen and Hsiu-Yu Yu
Polymers 2023, 15(24), 4711; https://doi.org/10.3390/polym15244711 - 14 Dec 2023
Viewed by 969
Abstract
The formed morphology during phase separation is crucial for determining the properties of the resulting product, e.g., a functional membrane. However, an accurate morphology prediction is challenging due to the inherent complexity of molecular interactions. In this study, the phase separation of a [...] Read more.
The formed morphology during phase separation is crucial for determining the properties of the resulting product, e.g., a functional membrane. However, an accurate morphology prediction is challenging due to the inherent complexity of molecular interactions. In this study, the phase separation of a two-dimensional model polymer solution is investigated. The spinodal decomposition during the formation of polymer-rich domains is described by the Cahn–Hilliard equation incorporating the Flory–Huggins free energy description between the polymer and solvent. We circumvent the heavy burden of precise morphology prediction through two aspects. First, we systematically analyze the degree of impact of the parameters (initial polymer volume fraction, polymer mobility, degree of polymerization, surface tension parameter, and Flory–Huggins interaction parameter) in a phase-separating system on morphological evolution characterized by geometrical fingerprints to determine the most influential factor. The sensitivity analysis provides an estimate for the error tolerance of each parameter in determining the transition time, the spinodal decomposition length, and the domain growth rate. Secondly, we devise a set of physics-informed neural networks (PINN) comprising two coupled feedforward neural networks to represent the phase-field equations and inversely discover the value of the embedded parameter for a given morphological evolution. Among the five parameters considered, the polymer–solvent affinity is key in determining the phase transition time and the growth law of the polymer-rich domains. We demonstrate that the unknown parameter can be accurately determined by renormalizing the PINN-predicted parameter by the change of characteristic domain size in time. Our results suggest that certain degrees of error are tolerable and do not significantly affect the morphology properties during the domain growth. Moreover, reliable inverse prediction of the unknown parameter can be pursued by merely two separate snapshots during morphological evolution. The latter largely reduces the computational load in the standard data-driven predictive methods, and the approach may prove beneficial to the inverse design for specific needs. Full article
(This article belongs to the Special Issue Molecular Dynamics Simulation of Polymer for Absorption and Separation Applications)
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19 pages, 16138 KiB  
Article
Self-Assembly of Symmetric Copolymers in Slits with Inert and Attractive Walls
by Tomáš Blovský, Karel Šindelka, Zuzana Limpouchová and Karel Procházka
Polymers 2023, 15(22), 4458; https://doi.org/10.3390/polym15224458 - 18 Nov 2023
Viewed by 708
Abstract
Although the behavior of the confined semi-dilute solutions of self-assembling copolymers represents an important topic of basic and applied research, it has eluded the interest of scientists. Extensive series of dissipative particle dynamics simulations have been performed on semi-dilute solutions of A5 [...] Read more.
Although the behavior of the confined semi-dilute solutions of self-assembling copolymers represents an important topic of basic and applied research, it has eluded the interest of scientists. Extensive series of dissipative particle dynamics simulations have been performed on semi-dilute solutions of A5B5 chains in a selective solvent for A in slits using a DL-MESO simulation package. Simulations of corresponding bulk systems were performed for comparison. This study shows that the associates in the semi-dilute bulk solutions are partly structurally organized. Mild steric constraints in slits with non-attractive walls hardly affect the size of the associates, but they promote their structural arrangement in layers parallel to the slit walls. Attractive walls noticeably affect the association process. In slits with mildly attractive walls, the adsorption competes with the association process. At elevated concentrations, the associates start to form in wide slits when the walls are sparsely covered by separated associates, and the association process prevents the full coverage of the surface. In slits with strongly attractive walls, adsorption is the dominant behavior. The associates form in wide slits at elevated concentrations only after the walls are completely and continuously covered by the adsorbed chains. Full article
(This article belongs to the Special Issue Molecular Dynamics Simulation of Polymer for Absorption and Separation Applications)
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19 pages, 2024 KiB  
Article
A Molecular Dynamics Study of Single-Gas and Mixed-Gas N2 and CH4 Transport in Triptycene-Based Polyimide Membranes
by Ioannis Tanis, David Brown, Sylvie Neyertz, Milind Vaidya, Jean-Pierre Ballaguet, Sebastien Duval and Ahmad Bahamdan
Polymers 2023, 15(18), 3811; https://doi.org/10.3390/polym15183811 - 18 Sep 2023
Viewed by 851
Abstract
Fluorinated polyimides incorporated with triptycene units have gained growing attention over the last decade since they present potentially interesting selectivities and a higher free volume with respect to their triptycene-free counterparts. This work examines the transport of single-gas and mixed-gas N2 and [...] Read more.
Fluorinated polyimides incorporated with triptycene units have gained growing attention over the last decade since they present potentially interesting selectivities and a higher free volume with respect to their triptycene-free counterparts. This work examines the transport of single-gas and mixed-gas N2 and CH4 in the triptycene-based 6FDA-BAPT homopolyimide and in a block 15,000 g mol−1/15,000 g mol−1 6FDA-mPDA/BAPT copolyimide by using molecular dynamics (MD) simulations. The void-space analyses reveal that, while the free volume consists of small-to-medium holes in the 6FDA-BAPT homopolyimide, there are more medium-to-large holes in the 6FDA-mPDA/BAPT copolyimide. The single-gas sorption isotherms for N2 and CH4 over the 0–70 bar range at 338.5 K show that both gases are more soluble in the block copolyimide, with a higher affinity for methane. CH4 favours sites with the most favourable energetic interactions, while N2 probes more sites in the matrices. The volume swellings remain limited since neither N2 nor CH4 plasticise penetrants. The transport of a binary-gas 2:1 CH4/N2 mixture is also examined in both polyimides under operating conditions similar to those used in current natural gas processing, i.e., at 65.5 bar and 338.5 K. In the mixed-gas simulations, the solubility selectivities in favour of CH4 are enhanced similarly in both matrices. Although diffusion is higher in 6FDA-BAPT/6FDA-mPDA, the diffusion selectivities are also close. Both triptycene-based polyimides under study favour, to a similar extent, the transport of methane over that of nitrogen under the conditions studied. Full article
(This article belongs to the Special Issue Molecular Dynamics Simulation of Polymer for Absorption and Separation Applications)
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16 pages, 6871 KiB  
Article
Molecular Weight Segregation and Thermal Conductivity of Polydisperse Wax–Graphene Nanocomposites
by Maarten Boomstra, Bernard Geurts and Alexey Lyulin
Polymers 2023, 15(9), 2175; https://doi.org/10.3390/polym15092175 - 03 May 2023
Cited by 1 | Viewed by 1436
Abstract
Paraffin waxes are a promising material for heat storage with high energy density. Their low thermal conductivity, which limits the speed of charging and discharging in heat buffers, was previously shown to be improved by adding graphene nanofillers. In the present study, using [...] Read more.
Paraffin waxes are a promising material for heat storage with high energy density. Their low thermal conductivity, which limits the speed of charging and discharging in heat buffers, was previously shown to be improved by adding graphene nanofillers. In the present study, using molecular dynamics simulations, the segregation by molecular weight of polydisperse paraffin near graphene flakes is investigated. In liquid bidisperse paraffin composed of decane and triacontane, an aligned layer containing mainly triacontane was observed next to the graphene. Upon slow cooling, the wax crystallised into distinct layers parallel to the graphene sheet, with much stronger segregation by molecular weight than in the crystallised bidisperse wax without graphene. For polydisperse wax, the segregation effect was much less pronounced. The molten paraffin had a somewhat higher concentration of the longest chains in the first layers next to the graphene, but during crystallisation, the molecular weight segregation was only slightly increased. Measurements of crystallinity using an alternative version of the method developed by Yamamoto showed that the layers of wax were highly aligned parallel to the graphene, both in the solid state with all wax crystallised and in the liquid state with one layer of aligned wax above and below the graphene. Thermal conductivity was increased in planes parallel to the graphene flakes. The strong segregation of chain lengths in the bidisperse wax resulted in clear differences in thermal conductivity in the segregated regions. The less segregated polydisperse wax showed less variation in thermal conductivity. Full article
(This article belongs to the Special Issue Molecular Dynamics Simulation of Polymer for Absorption and Separation Applications)
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15 pages, 3185 KiB  
Article
Modelling across Multiple Scales to Design Biopolymer Membranes for Sustainable Gas Separations: 1—Atomistic Approach
by Kseniya Papchenko, Eleonora Ricci and Maria Grazia De Angelis
Polymers 2023, 15(7), 1805; https://doi.org/10.3390/polym15071805 - 06 Apr 2023
Cited by 3 | Viewed by 1243
Abstract
In this work, we assessed the CO2 and CH4 sorption and transport in copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate (PHBV), which showed good CO2 capture potential in our previous papers, thanks to their good solubility–selectivity, and are potential biodegradable alternatives to [...] Read more.
In this work, we assessed the CO2 and CH4 sorption and transport in copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate (PHBV), which showed good CO2 capture potential in our previous papers, thanks to their good solubility–selectivity, and are potential biodegradable alternatives to standard membrane-separation materials. Experimental tests were carried out on a commercial material containing 8% of 3-hydroxyvalerate (HV), while molecular modelling was used to screen the performance of the copolymers across the entire composition range by simulating structures with 0%, 8%, 60%, and 100% HV, with the aim to provide a guide for the selection of the membrane material. The polymers were simulated using molecular dynamics (MD) models and validated against experimental density, solubility parameters, and X-ray diffraction. The CO2/CH4 solubility–selectivity predicted by the Widom insertion method is in good agreement with experimental data, while the diffusivity–selectivity obtained via mean square displacement is somewhat overestimated. Overall, simulations indicate promising behaviour for the homopolymer containing 100% of HV. In part 2 of this series of papers, we will investigate the same biomaterials using a macroscopic model for polymers and compare the accuracy and performance of the two approaches. Full article
(This article belongs to the Special Issue Molecular Dynamics Simulation of Polymer for Absorption and Separation Applications)
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