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

Deadline for manuscript submissions: closed (31 October 2018) | Viewed by 51631

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Dr. Brendan Howlin

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Department of Chemistry, FEPS, University of Surrey, Surrey GU2 7XH, UK
Interests: polymer modelling; QSPR; molecular dynamics; molecular mechanics; composites; structural resins; benzoxazines; simulation of charring of polymers; reactive molecular dynamics; molecular orbitals; DFT
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Special Issue Information

Dear Colleagues,

This Special Issue focus on the current state-of-the-art of simulations of polymeric materials. The simulation of polymeric materials has come of age and true prediction of physical and mechanical properties is feasible. Polymeric materials are used widely in coating and structural applications, as well as components of composites.

Papers are sought that discuss the latest research in the area or summarize selected areas of the field. The scope of the Special Issue encompasses all methods of polymer simulation from the atomistic to larger scale simulation.

Of particular interest are developments that cover the length scales of simulation and those that illustrate the growing ability to use molecular orbital methods to gain insight into structure/function.

Dr. Brendan Howlin
Guest Editor

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

Polymer simulation
Mechanical Properties simulation
DFT
Molecular mechanics
Molecular dynamics
QSPR
RMD

Related Special Issue

Simulations of Polymers II in Polymers (9 articles)

Published Papers (13 papers)

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Research

12 pages, 2547 KiB

Open AccessArticle

Calculated Terahertz Spectra of Glycine Oligopeptide Solutions Confined in Carbon Nanotubes

by Dongxiong Ling, Mingkun Zhang, Jianxun Song and Dongshan Wei

Polymers 2019, 11(2), 385; https://doi.org/10.3390/polym11020385 - 25 Feb 2019

Cited by 3 | Viewed by 3081

Abstract

To reduce the intense terahertz (THz) wave absorption of water and increase the signal-to-noise ratio, the THz spectroscopy detection of biomolecules usually operates using the nanofluidic channel technologies in practice. The effects of confinement due to the existence of nanofluidic channels on the conformation and dynamics of biomolecules are well known. However, studies of confinement effects on the THz spectra of biomolecules are still not clear. In this work, extensive all-atom molecular dynamics simulations are performed to investigate the THz spectra of the glycine oligopeptide solutions in free and confined environments. THz spectra of the oligopeptide solutions confined in carbon nanotubes (CNTs) with different radii are calculated and compared. Results indicate that with the increase of the degree of confinement (the reverse of the radius of CNT), the THz absorption coefficient decreases monotonically. By analyzing the diffusion coefficient and dielectric relaxation dynamics, the hydrogen bond life, and the vibration density of the state of the water molecules in free solution and in CNTs, we conclude that the confinement effects on the THz spectra of biomolecule solutions are mainly to slow down the dynamics of water molecules and hence to reduce the THz absorption of the whole solution in confined environments. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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17 pages, 5949 KiB

Open AccessArticle

Hydrogen Storage, Magnetism and Electrochromism of Silver Doped FAU Zeolite: First-Principles Calculations and Molecular Simulations

by Wei-Feng Sun, Yu-Xuan Sun, Shu-Ting Zhang and Ming-He Chi

Polymers 2019, 11(2), 279; https://doi.org/10.3390/polym11020279 - 07 Feb 2019

Cited by 9 | Viewed by 3313

Abstract

The complex configuration, H₂ adsorption binding energy, magnetic, and optical properties of FAU zeolites with Ag cations loaded by ion exchange in the vacant dielectric cavities were investigated by employing the first-principles calculations with all-electron-relativistic numerical atom-orbitals scheme and the Metropolis Monte Carlo molecular simulations. The visible absorption spectrum peaked at distinct wavelengths arranging from red or green to blue colors when changing the net charge load, due to the produced various redox states of Ag cations exchanging at multiple Li⁺-substituted sites. The spin population analyses indicate the ferrimagnetic coupling between Al–O–Si framework and Ag cations originates from the major ferromagnetic spin polarization in Ag cation cluster coordinating with sodalite cages, with the net spins appreciably depending on the Ag content and exchange site. The H₂ adsorption capacities and binding energies represent significant dependence on the content, location, and electronic property of Ag cations introduced into the FAU zeolites. The evident decrease of H₂ adsorption binding energy with increased loading concentration demonstrates repulsive interaction between H₂ molecules and heterogeneous adsorption configuration on Ag cations. The adsorption sites of H₂ sorted by the binding energy with different adsorption configurations were correlated with exchange sites of Ag cations under different Ag loading to comprehend the H₂ adsorption mechanism. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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19 pages, 2962 KiB

Open AccessArticle

Explicit Ion Effects on the Charge and Conformation of Weak Polyelectrolytes

by Vikramjit S. Rathee, Hythem Sidky, Benjamin J. Sikora and Jonathan K. Whitmer

Polymers 2019, 11(1), 183; https://doi.org/10.3390/polym11010183 - 21 Jan 2019

Cited by 24 | Viewed by 6027

Abstract

The titration behavior of weak polyelectrolytes is of high importance, due to their uses in new technologies including nanofiltration and drug delivery applications. A comprehensive picture of polyelectrolyte titration under relevant conditions is currently lacking, due to the complexity of systems involved in the process. One must contend with the inherent structural and solvation properties of the polymer, the presence of counterions, and local chemical equilibria enforced by background salt concentration and solution acidity. Moreover, for these cases, the systems of interest have locally high concentrations of monomers, induced by polymer connectivity or confinement, and thus deviate from ideal titration behavior. This work furthers knowledge in this limit utilizing hybrid Monte Carlo–Molecular Dynamics simulations to investigate the influence of salt concentration,

{pK}_{a}

, pH, and counterion valence in determining the coil-to-globule transition of poorly solvated weak polyelectrolytes. We characterize this transition at a range of experimentally relevant salt concentrations and explicitly examine the role multivalent salts play in determining polyelectrolyte ionization behavior and conformations. These simulations serve as an essential starting point in understanding the complexation between weak polyelectrolytes and ion rejection of self-assembled copolymer membranes. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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17 pages, 1519 KiB

Open AccessArticle

Synchronized Molecular-Dynamics Simulation of the Thermal Lubrication of an Entangled Polymeric Liquid

by Shugo Yasuda

Polymers 2019, 11(1), 131; https://doi.org/10.3390/polym11010131 - 13 Jan 2019

Cited by 7 | Viewed by 4005

Abstract

The thermal lubrication of an entangled polymeric liquid in wall-driven shear flows between parallel plates is investigated by using a multiscale hybrid method, coupling molecular dynamics and hydrodynamics (i.e., the synchronized molecular dynamics method). The temperature of the polymeric liquid rapidly increases due to viscous heating once the drive force exceeds a certain threshold value, and the rheological properties drastically change at around the critical drive force. In the weak viscous-heating regime, the conformation of polymer chains is dominated by the flow field so that the polymers are more elongated as the drive force increases. However, in the large viscous-heating regime, the conformation dynamics is dominated by the thermal agitation of polymer chains so that the conformation of polymers recovers more uniform and random structures as the drive force increases, even though the local shear flows are further enhanced. Remarkably, this counter-intuitive transitional behavior gives an interesting re-entrant transition in the stress–optical relation, where the linear stress–optical relation approximately holds even though each of the macroscopic quantities behaves nonlinearly. Furthermore, the shear thickening behavior is also observed in the large viscous-heating regime—this was not observed in a series of previous studies on an unentangled polymer fluid. This qualitative difference of the thermo-rheological property between the entangled and unentangled polymer fluids gives completely different velocity profiles in the thermal lubrication system. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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25 pages, 9224 KiB

Open AccessArticle

Confined Polymers as Self-Avoiding Random Walks on Restricted Lattices

by Javier Benito, Nikos Ch. Karayiannis and Manuel Laso

Polymers 2018, 10(12), 1394; https://doi.org/10.3390/polym10121394 - 15 Dec 2018

Cited by 8 | Viewed by 4019

Abstract

Polymers in highly confined geometries can display complex morphologies including ordered phases. A basic component of a theoretical analysis of their phase behavior in confined geometries is the knowledge of the number of possible single-chain conformations compatible with the geometrical restrictions and the established crystalline morphology. While the statistical properties of unrestricted self-avoiding random walks (SAWs) both on and off-lattice are very well known, the same is not true for SAWs in confined geometries. The purpose of this contribution is (a) to enumerate the number of SAWs on the simple cubic (SC) and face-centered cubic (FCC) lattices under confinement for moderate SAW lengths, and (b) to obtain an approximate expression for their behavior as a function of chain length, type of lattice, and degree of confinement. This information is an essential requirement for the understanding and prediction of entropy-driven phase transitions of model polymer chains under confinement. In addition, a simple geometric argument is presented that explains, to first order, the dependence of the number of restricted SAWs on the type of SAW origin. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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18 pages, 1333 KiB

Open AccessArticle

Parallel Tempering Monte Carlo Studies of Phase Transition of Free Boundary Planar Surfaces

by Andrey Shobukhov and Hiroshi Koibuchi

Polymers 2018, 10(12), 1360; https://doi.org/10.3390/polym10121360 - 08 Dec 2018

Viewed by 2978

Abstract

We numerically study surface models defined on hexagonal disks with a free boundary. 2D surface models for planar surfaces have recently attracted interest due to the engineering applications of functional materials such as graphene and its composite with polymers. These 2D composite meta-materials are strongly influenced by external stimuli such as thermal fluctuations if they are sufficiently thin. For this reason, it is very interesting to study the shape stability/instability of thin 2D materials against thermal fluctuations. In this paper, we study three types of surface models including Landau-Ginzburg (LG) and Helfirch-Polyakov models defined on triangulated hexagonal disks using the parallel tempering Monte Carlo simulation technique. We find that the planar surfaces undergo a first-order transition between the smooth and crumpled phases in the LG model and continuous transitions in the other two models. The first-order transition is relatively weak compared to the transition on spherical surfaces already reported. The continuous nature of the transition is consistent with the reported results, although the transitions are stronger than that of the reported ones. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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15 pages, 3724 KiB

Open AccessArticle

Exploring Structure–Property Relationships in Aromatic Polybenzoxazines Through Molecular Simulation

by Scott Thompson, Corinne A. Stone, Brendan J. Howlin and Ian Hamerton

Polymers 2018, 10(11), 1250; https://doi.org/10.3390/polym10111250 - 12 Nov 2018

Cited by 7 | Viewed by 2795

Abstract

A series of commercial difunctional benzoxazine monomers are characterized using thermal and thermo-mechanical techniques before constructing representative polymer networks using molecular simulation techniques. Good agreement is obtained between replicate analyses and for the kinetic parameters obtained from differential scanning calorimetry data (and determined using the methods of Kissinger and Ozawa). Activation energies range from 85 to 108 kJ/mol (Kissinger) and 89 to 110 kJ/mol (Ozawa) for the uncatalyzed thermal polymerization reactions, which achieve conversions of between 85% and 97%. Glass transition temperatures determined from differential scanning calorimetry and dynamic mechanical thermal analysis are comparable, ranging from BA-a (151 °C, crosslink density 3.6 × 10⁻³ mol cm⁻³) containing the bisphenol A moiety to BP-a, based on a phenolphthalein bridge (239 to 256 °C, crosslink density 5.5 to 18.4 × 10⁻³ mol cm⁻³, depending on formulation). Molecular dynamics simulations of the polybenzoxazines generally agree well with empirical data, indicating that representative networks have been modelled. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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15 pages, 5092 KiB

Open AccessArticle

Thinning Approximation for Calculating Two-Dimensional Scattering Patterns in Dissipative Particle Dynamics Simulations under Shear Flow

by Katsumi Hagita, Takahiro Murashima and Nobuyuki Iwaoka

Polymers 2018, 10(11), 1224; https://doi.org/10.3390/polym10111224 - 03 Nov 2018

Cited by 5 | Viewed by 3401

Abstract

Modifications to improve thinning approximation (TA) were considered in order to calculate two-dimensional scattering patterns (2DSPs) for dissipative particle dynamics (DPD) simulations of polymer melts under a shear flow. We proposed multipoint TA and adaptive TA because the bond lengths in DPD chains vary widely when compared to those in Kremer–Grest (KG) chains, and the effectiveness of these two types of TA for the two major DPD parameter sets were investigated. In this paper, we report our findings on the original DPD model with soft bonds and that with rigid bonds. Based on the behavior of the 2DSPs and the distribution of orientations of the bond vectors, two spot patterns originating from the oriented chain correlations were observed when distinct distributions of the highly oriented bond vectors in the shear direction were obtained. For multipoint TA, we concluded that at least two additional midpoints (

n_{mid} \geq 2)

are required to clearly observe the two spot patterns. For adaptive TA, a dividing distance of

l_{ATA} \leq 0.4

is sufficient for clear observation, which is consistent with the requirement of

n_{mid} \geq 2

for multipoint TA. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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20 pages, 7139 KiB

Open AccessArticle

Designing the Slide-Ring Polymer Network with both Good Mechanical and Damping Properties via Molecular Dynamics Simulation

by Zhiyu Zhang, Guanyi Hou, Jianxiang Shen, Jun Liu, Yangyang Gao, Xiuying Zhao and Liqun Zhang

Polymers 2018, 10(9), 964; https://doi.org/10.3390/polym10090964 - 01 Sep 2018

Cited by 25 | Viewed by 6381

Abstract

Through coarse-grained molecular dynamics simulation, we have successfully designed the chemically cross-linked (fixed junction) and the slide-ring (SR) systems. Firstly, we examine the dynamic properties such as the mean-square displacement, the bond, and the end-to-end autocorrelation functions as a function of the cross-linking density, consistently pointing out that the SR system exhibits much lower mobility compared with the fixed junction one at the same cross-linking density. This is further validated by a relatively higher glass transition temperature for the SR system compared with that of the fixed junction one. Then, we calculated the effect of the cross-linking density on the stretch-recovery behavior for the SR and fixed junction systems. Although the chain orientation of the SR system is higher than that of the fixed-junction system, the tensile stress is smaller than the latter. We infer that much greater chain sliding can occur during the stretch, because the movable ring structure homogeneously sustains the external force of the SR system, which, therefore, leads to much larger permanent set and higher hysteresis during the recovery process compared with the fixed-junction one. Based on the stretch-recovery behavior for various cross-linking densities, we obtain the change of the hysteresis loss, which is larger for the SR system than that of the fixed junction system. Lastly, we note that the relatively bigger compressive stress for the SR system results from the aggregation of the rigid rings compared with the fixed junction system. In general, compared with the traditionally cross-linked system, a deep molecular-level insight into the slide-ring polymer network is offered and thus is believed to provide some guidance to the design and preparation of the slide-ring polymer network with both good mechanical and damping properties. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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18 pages, 6039 KiB

Open AccessArticle

Coupled Hygro-Mechanical Finite Element Method on Determination of the Interlaminar Shear Modulus of Glass Fiber-Reinforced Polymer Laminates in Bridge Decks under Hygrothermal Aging Effects

by Xu Jiang, Chengwei Luo, Xuhong Qiang, Qilin Zhang, Henk Kolstein and Frans Bijlaard

Polymers 2018, 10(8), 845; https://doi.org/10.3390/polym10080845 - 01 Aug 2018

Cited by 9 | Viewed by 3332

Abstract

To investigate the mechanical degradation of the shear properties of glass fiber-reinforced polymer (GFRP) laminates in bridge decks under hygrothermal aging effects, short-beam shear tests were performed following the ASTM test standard (ASTM D790-10A). Based on the coupled hygro-mechanical finite element (FE) analysis method, an inverse parameter identification approach based on short-beam shear tests was developed and then employed to determine the environment-dependent interlaminar shear modulus of GFRP laminates. Subsequently, the shear strength and modulus of dry (0% M_t/M_∞), moisture unsaturated (30% M_t/M_∞ and 50% M_t/M_∞), and moisture saturated (100% M_t/M_∞) specimens at test temperatures of both 20 °C and 40 °C were compared. One cycle of the moisture absorption–desorption process was also investigated to address how the moisture-induced residual damage degrades the shear properties of GFRP laminates. The results revealed that the shear strength and modulus of moisture-saturated GFRP laminates decreased significantly, and the elevated testing temperature (40 °C) aggravated moisture-induced mechanical degradation. Moreover, an unrecoverable loss of shear properties for the GFRP laminates enduring one cycle of the moisture absorption–desorption process was evident. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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13 pages, 5062 KiB

Open AccessArticle

Molecular Dynamics Simulations on the Thermal Decomposition of Meta-Aramid Fibers

by Fei Yin, Chao Tang, Qian Wang, Xiong Liu and Yujing Tang

Polymers 2018, 10(7), 691; https://doi.org/10.3390/polym10070691 - 21 Jun 2018

Cited by 21 | Viewed by 4137

Abstract

The thermal decomposition mechanism of a meta-aramid fiber was simulated at the atomic level using the ReaxFF reactive force field. The simulation results indicated that the main initial decomposition positions of the meta-aramid fiber elements were C_{aromatic ring}–N and C=O, which could be used as targets for the modification of meta-aramid fibers. The meta-aramid fiber elements first decomposed into C6–C13 and then into smaller segments and micromolecular gases. The temperature was shown to be the key factor affecting the thermal decomposition of the meta-aramid fibers. More complex compositions and stable gases were produced at high temperatures than at lower temperatures. HCN was a decomposition product at high temperature, suggesting that its presence could be used for detecting thermal faults in meta-aramid fibers. Generation path tracing of the thermal decomposition products NH₃ and H₂O was also performed. NH₃ was produced when the NH₂ group captured an H atom adjacent to the system. H₂O was formed after a carbonyl group captured an H atom, became a hydroxyl group, with subsequent intramolecular dehydration or intermolecular hydrogen abstraction. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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23 pages, 44886 KiB

Open AccessArticle

Finite-Element Investigation of the Structural Behavior of Basalt Fiber Reinforced Polymer (BFRP)- Reinforced Self-Compacting Concrete (SCC) Decks Slabs in Thompson Bridge

by Lingzhu Zhou, Yu Zheng and Susan E. Taylor

Polymers 2018, 10(6), 678; https://doi.org/10.3390/polym10060678 - 18 Jun 2018

Cited by 15 | Viewed by 4011

Abstract

The need for a sustainable development and improved whole life performance of concrete infrastructure has led to the requirement of more durable and sustainable concrete bridges alongside accurate predictive analysis tools. Using the combination of Self-Compacting Concrete (SCC) with industrial by-products and fiber-reinforced polymer (FRP), reinforcement is anticipated to address the concerns of high carbon footprint and corrosion in traditional steel-reinforced concrete structures. This paper presents a numerical investigation of the structural behavior of basalt fiber-reinforced polymer (BFRP)-reinforced SCC deck slabs in a real bridge, named Thompson Bridge, constructed in Northern Ireland, U.K. A non-linear finite element (FE) model is proposed by using ABAQUS 6.10 in this study, which is aimed at extending the previous investigation of the field test in Thompson Bridge. The results of this field test were used to validate the accuracy of the proposed finite element model. The results showed good agreement between the test results and the numerical results; more importantly, the compressive membrane action (CMA) inside the slabs could be well demonstrated by this FE model. Subsequently, a series of parametric studies was conducted to investigate the influence of different parameters on the structural performance of the deck slabs in Thompson Bridge. The results of the analyses are discussed, and conclusions on the behavior of the SCC deck slabs reinforced by BFRP bars are presented. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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18 pages, 23068 KiB

Open AccessArticle

A Numerical Method Charactering the Electromechanical Properties of Particle Reinforced Composite Based on Statistics

by Mengzhou Chang and Zhenqing Wang

Polymers 2018, 10(4), 426; https://doi.org/10.3390/polym10040426 - 11 Apr 2018

Cited by 6 | Viewed by 3409

Abstract

A novel model for a network of polymer chains is proposed considering the distribution of polymer chains inside the composite in this work. Some factors that influence the distribution of polymer chains are quantitatively investigated, such as external surface geometry, internal filler, and local deformation. Furthermore, the Maxwell stress induced by an electric field is characterized by the statistics of local charge density, as the basic analyzing electromechanical properties of materials. In particular, taking the non-uniform distribution of polymer chains into account, the electromechanical properties of two materials—VHB 4910 and CaCu₃Ti₄O₁₂-polydimethylsiloxane (CCTO-PDMS)—are investigated to validate the applicability of the proposed model. The comparison between simulation results and experimental results from existing literature shows that the model was successfully employed to predict the electromechanical properties of polymer composites. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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