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Polymers
Special Issues
Molecular Simulation and Modeling of Polymers II
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Molecular Simulation and Modeling of Polymers II

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

Deadline for manuscript submissions: closed (28 February 2024) | Viewed by 3831

Special Issue Editors

Dr. Cristina Stancu

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Guest Editor
Faculty of Electrical Engineering, Electrotechnical Material Laboratory, University Politehnica of Bucharest, Splaiul Independentei 313, 060042 Bucharest, Romania
Interests: polymers; aging; properties of polymers; simulation; modeling
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Radu Setnescu

E-Mail Website
Guest Editor
1. Faculty of Sciences and Arts, Department of Science s and Advanced Technologies, Valahia University of Targoviste, 13 Aleea Sinaia, 130004 Targoviste, Romania
2. Radiation Chemistry Laboratory, National R&D Institute of Electrical Engineering (ICPE-CA), 313 Splaiul Unirii, 030138 Bucharest, Romania
Interests: radiation processing; aging; degradation; infrared spectroscopy; thermal analysis

Special Issue Information

Dear Colleagues,

Following the success of the Special Issue of Polymers entitled “Molecular Simulation and Modeling of Polymers”, https://www.mdpi.com/journal/polymers/special_issues/mol_simul_model_polym，we are delighted to reopen the Special Issue, now entitled “Polymer Molecular Simulation and Modeling of Polymers II”.

In the last decade, computer simulation has developed as a powerful tool for studying the properties of polymer materials, especially for engineers. Computer simulation can study a model of a complex many-body system in full detail without involving mathematical approximations. At the same time, making comparisons using experiments helps to validate and systematically improve the model. In fact, the use of computer simulation in this way is an iterative process by which the understanding of complex materials and processes can be significantly improved step by step.

The molecular simulation of bulk polymers has been applied to study the properties of polymers, such as glass transition temperatures, diffusion of small molecules, plastic and elastic deformation, and mechanisms of molecular mobility.

The Special Issue aims to publish new research work that advances the understanding and prediction of material behavior at scales from atomistic to macroscopic using modeling and simulation.

We are pleased to announce that the issue of Polymers will be devoted to Molecular Simulation and Modeling of Polymers. The following non-exclusive list of topics may serve as a guideline for prospective authors:

  • Structure of polymers;
  • Properties;
  • Molecular dynamics simulations;
  • Development of new modeling and simulation techniques;
  • Applications.

Dr. Cristina Stancu
Prof. Dr. Radu Setnescu
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

  • modeling
  • simulations
  • molecular dynamics
  • polymers
  • polymers composites
  • interfaces
  • diffusion
  • applications

Published Papers (3 papers)

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Research

13 pages, 2584 KiB  
Article
Kinetics Study of PVA Polymer by Model-Free and Model-Fitting Methods Using TGA
by Zaid Abdulhamid Alhulaybi and Ibrahim Dubdub
Polymers 2024, 16(5), 629; https://doi.org/10.3390/polym16050629 - 26 Feb 2024
Viewed by 1051
Abstract
Thermogravimetric Analysis (TGA) serves a pivotal technique for evaluating the thermal behavior of Polyvinyl alcohol (PVA), a polymer extensively utilized in the production of fibers, films, and membranes. This paper targets the kinetics of PVA thermal degradation using high three heating rate range [...] Read more.
Thermogravimetric Analysis (TGA) serves a pivotal technique for evaluating the thermal behavior of Polyvinyl alcohol (PVA), a polymer extensively utilized in the production of fibers, films, and membranes. This paper targets the kinetics of PVA thermal degradation using high three heating rate range 20, 30, and 40 K min−1. The kinetic study was performed using six model-free methods: Freidman (FR), Flynn-Wall-Qzawa (FWO), Kissinger-Akahira-Sunose (KAS), Starink (STK), Kissinger (K), and Vyazovkin (VY) for the determination of the activation energy (Ea). TGA showed two reaction stages: the main one at 550–750 K and the second with 700–810 K. But only the first step has been considered in calculating Ea. The average activation energy values for the conversion range (0.1–0.7) are between minimum 104 kJ mol−1 by VY to maximum 199 kJ mol−1 by FR. Model-fitting has been applied by combing Coats–Redfern (CR) with the master plot (Criado’s) to identify the most convenient reaction mechanism. Ea values gained by the above six models were very similar with the average value of (126 kJ mol−1) by CR. The reaction order models-Second order (F2) was recommended as the best mechanism reaction for PVA pyrolysis. Mechanisms were confirmed by the compensation effect. Finally, (∆H, ∆G, and ∆S) parameters were presented and proved that the reaction is endothermic. Full article
(This article belongs to the Special Issue Molecular Simulation and Modeling of Polymers II)
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26 pages, 33311 KiB  
Article
Single-Bubble Rising in Shear-Thinning and Elastoviscoplastic Fluids Using a Geometric Volume of Fluid Algorithm
by Ahmad Fakhari and Célio Fernandes
Polymers 2023, 15(16), 3437; https://doi.org/10.3390/polym15163437 - 17 Aug 2023
Viewed by 1121
Abstract
The motion of air bubbles within a liquid plays a crucial role in various aspects including heat transfer and material quality. In the context of non-Newtonian fluids, such as elastoviscoplastic fluids, the presence of air bubbles significantly influences the viscosity of the liquid. [...] Read more.
The motion of air bubbles within a liquid plays a crucial role in various aspects including heat transfer and material quality. In the context of non-Newtonian fluids, such as elastoviscoplastic fluids, the presence of air bubbles significantly influences the viscosity of the liquid. This study presents the development of an interface-capturing method for multiphase viscoelastic fluid flow simulations. The proposed algorithm utilizes a geometric volume of fluid (isoAdvector) approach and incorporates a reconstructed distance function (RDF) to determine interface curvature instead of relying on volume fraction gradients. Additionally, a piecewise linear interface construction (PLIC) scheme is employed in conjunction with the RDF-based interface reconstruction for improved accuracy and robustness. The validation of the multiphase viscoelastic PLIC-RDF isoAdvector (MVP-RIA) algorithm involved simulations of the buoyancy-driven rise of a bubble in fluids with varying degrees of rheological complexity. First, the newly developed algorithm was applied to investigate the buoyancy-driven rise of a bubble in a Newtonian fluid on an unbounded domain. The results show excellent agreement with experimental and theoretical findings, capturing the bubble shape and velocity accurately. Next, the algorithm was extended to simulate the buoyancy-driven rise of a bubble in a viscoelastic shear-thinning fluid described by the Giesekus constitutive model. As the influence of normal stress surpasses surface tension, the bubble shape undergoes a transition to a prolate or teardrop shape, often exhibiting a cusp at the bubble tail. This is in contrast to the spherical, ellipsoidal, or spherical-cap shapes observed in the first case study with a bubble in a Newtonian fluid. Lastly, the algorithm was employed to study the buoyancy-driven rise of a bubble in an unbounded elastoviscoplastic medium, modeled using the Saramito–Herschel–Bulkley constitutive equation. It was observed that in very small air bubbles within the elastoviscoplastic fluid, the dominance of elasticity and capillary forces restricts the degree of bubble deformation. As the bubble volume increases, lateral stretching becomes prominent, resulting in the emergence of two tails. Ultimately, a highly elongated bubble shape with sharper tails is observed. The results show that by applying the newly developed MVP-RIA algorithm, with a tangible coarser grid compared to the algebraic VOF method, an accurate solution is achieved. This will open doors to plenty of applications such as bubble columns in reactors, oil and gas mixtures, 3D printing, polymer processing, etc. Full article
(This article belongs to the Special Issue Molecular Simulation and Modeling of Polymers II)
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Graphical abstract

19 pages, 3928 KiB  
Article
Isotropic and Anisotropic Complex Refractive Index of PEDOT:PSS
by Lara Velasco Davoise, Rafael Peña Capilla and Ana M. Díez-Pascual
Polymers 2023, 15(15), 3298; https://doi.org/10.3390/polym15153298 - 4 Aug 2023
Viewed by 1247
Abstract
In this work, the complex refractive indexes of seven PEDOT:PSS samples, three with isotropic behavior and four with optical anisotropy, were determined. For the anisotropic samples, the ordinary and extraordinary components of the refractive index were described. The effect of the film thickness, [...] Read more.
In this work, the complex refractive indexes of seven PEDOT:PSS samples, three with isotropic behavior and four with optical anisotropy, were determined. For the anisotropic samples, the ordinary and extraordinary components of the refractive index were described. The effect of the film thickness, measurement technique and preparation method on the extinction coefficient (k) and refractive index (n) of each sample was also discussed. Important differences (up to 20% in the average n) were found among the samples investigated. In most anisotropic films, the mean value of the extraordinary component was between 7 and 10% higher than that of the ordinary. In the three isotropic films, the average k rose when the film thickness increased. Moreover, the different sets of refractive index data were fitted to three different models: the original Forouhi–Bloomer model, the Liu (2007) model and the revised version of the Forouhi–Bloomer model (2019). In general, Liu’s model gave better results, with small errors in n and k (<7.81 and 4.68%, respectively, in all the cases). However, this model had seven fitting parameters, which led to significantly longer computation time than the other two models. The influence of the differences in the measurement of the complex refractive index on the simulation of the optical properties of PEDOT:PSS multilayers was discussed. The results showed that n must be known precisely to accurately calculate the light absorption in a multilayer, without ignoring the isotropic or anisotropic behavior of the material or the influence of the layer thickness on its optical properties. This study aids in the development of simulation and optimization tools that allow understanding the optical properties of PEDOT:PSS films for their potential applications in organic optoelectronic devices, such as organic solar cells. Full article
(This article belongs to the Special Issue Molecular Simulation and Modeling of Polymers II)
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