A Stochastic Dynamics Simulation of Viscoelastic Properties of Polymer Blends: Intermolecular Interaction Effects

1998 ◽  
Vol 18 (1-2) ◽  
pp. 1-16
Author(s):  
Taehyung Kim ◽  
Kyoungsei Choi ◽  
Won Ho Jo
Keyword(s):  
Shear Rate ◽  
Polymer Blends ◽  
Intermolecular Interaction ◽  
Viscoelastic Properties ◽  
Stochastic Dynamics ◽  
Structural Information ◽  
Model Systems ◽  
Dynamics Simulation ◽  
Radius Of Gyration ◽  
Orientation Factor

Abstract Stochastic dynamics simulations were performed to investigate the viscoelastic properties of polymer blends. In this simulation, three model systems with different intermolecular interactions are used to examine the effect of intermolecular interaction on the viscoelastic properties of polymer blends. Structural information such as the radius of gyration, orientation factor and radial distribution function of polymers is calculated from computer simulations as a function of shear rate and then is related to simulated viscoelastic properties of polymer blends. The effect of intermolecular interaction on the viscosity becomes different depending upon the magnitude of shear rate. At lower shear rate regions, more attractive intermolecular interaction results in lower viscosity due to chain stretching. But, at higher shear rate regions, more attractive interaction results in higher viscosity due to more dense packing of chains induced by the intermolecular attraction.

Investigation of the Microscopic Viscoelastic Property for Cross-linked Polymer Network by Molecular Dynamics Simulation

2011 ◽  
Vol 39 (1) ◽  
pp. 44-58 ◽  
Author(s):  
Y. Masumoto ◽  
Y. Iida
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Analytical Method ◽  
Viscoelastic Properties ◽  
Polymer Network ◽  
Dynamics Simulation ◽  
Coarse Grained ◽  
The Cross ◽  
Microscopic Dynamic ◽  
Coarse Grained Molecular Dynamics

Abstract The purpose of this work is to develop a new analytical method for simulating the microscopic mechanical property of the cross-linked polymer system using the coarse-grained molecular dynamics simulation. This new analytical method will be utilized for the molecular designing of the tire rubber compound to improve the tire performances such as rolling resistance and wet traction. First, we evaluate the microscopic dynamic viscoelastic properties of the cross-linked polymer using coarse-grained molecular dynamics simulation. This simulation has been conducted by the coarse-grained molecular dynamics program in the OCTA) (http://octa.jp/). To simplify the problem, we employ the bead-spring model, in which a sequence of beads connected by springs denotes a polymer chain. The linear polymer chains that are cross-linked by the cross-linking agents express the three-dimensional cross-linked polymer network. In order to obtain the microscopic dynamic viscoelastic properties, oscillatory deformation is applied to the simulation cell. By applying the time-temperature reduction law to this simulation result, we can evaluate the dynamic viscoelastic properties in the wide deformational frequency range including the rubbery state. Then, the stress is separated into the nonbonding stress and the bonding stress. We confirm that the contribution of the nonbonding stress is larger at lower temperatures. On the other hand, the contribution of the bonding stress is larger at higher temperatures. Finally, analyzing a change of microscopic structure in dynamic oscillatory deformation, we determine that the temperature/frequency dependence of bond stress response to a dynamic oscillatory deformation depends on the temperature dependence of the average bond length in the equilibrium structure and the temperature/frequency dependence of bond orientation. We show that our simulation is a useful tool for studying the microscopic properties of a cross-linked polymer.

scholarly journals Simulation of bonding effects in HRTEM images of light element materials

2011 ◽  
Vol 2 ◽  
pp. 394-404 ◽  
Author(s):  
Simon Kurasch ◽  
Jannik C Meyer ◽  
Daniela Künzel ◽  
Axel Groß ◽  
Ute Kaiser
Keyword(s):  
Density Functional ◽  
Structural Information ◽  
Hexagonal Boron Nitride ◽  
Light Element ◽  
Model Systems ◽  
Single Atom ◽  
Transmission Electron ◽  
Relative Contrast ◽  
Oxygen Substitution ◽  
Simulation Scheme

The accuracy of multislice high-resolution transmission electron microscopy (HRTEM) simulation can be improved by calculating the scattering potential using density functional theory (DFT) Gemming, T.; Möbus, G.; Exner, M.; Ernst, F.; Rühle, M. J. Microsc. 1998, 190, 89–98. doi:10.1046/j.1365-2818.1998.3110863.xDeng, B.; Marks, L. D. Acta Crystallogr., Sect. A 2006, 62, 208–216. doi:10.1107/S010876730601004X. This approach accounts for the fact that electrons in the specimen are redistributed according to their local chemical environment. This influences the scattering process and alters the absolute and relative contrast in the final image. For light element materials with well defined geometry, such as graphene and hexagonal boron nitride monolayers, the DFT based simulation scheme turned out to be necessary to prevent misinterpretation of weak signals, such as the identification of nitrogen substitutions in a graphene network. Furthermore, this implies that the HRTEM image does not only contain structural information (atom positions and atomic numbers). Instead, information on the electron charge distribution can be gained in addition. In order to produce meaningful results, the new input parameters need to be chosen carefully. Here we present details of the simulation process and discuss the influence of the main parameters on the final result. Furthermore we apply the simulation scheme to three model systems: A single atom boron and a single atom oxygen substitution in graphene and an oxygen adatom on graphene.

THE "FOLDING" BEHAVIORS OF HOMOPOLYMERS WITH ONE END FIXED

2004 ◽  
Vol 18 (15) ◽  
pp. 2123-2139 ◽  
Author(s):  
BIN XUE ◽  
JUN WANG ◽  
WEI WANG
Keyword(s):  
Molecular Dynamics ◽  
Chain Length ◽  
Conformational Changes ◽  
Canonical Ensemble ◽  
Interaction Strength ◽  
Simulation Method ◽  
Dynamics Simulation ◽  
Radius Of Gyration ◽  
Native Conformation ◽  
Collapse Temperature

We study the "folding" behaviors of homopolymers with one end fixed. By using canonical ensemble molecular dynamics simulation method, we observe the conformational changes during folding processes. Long chains collapse to the helical nuclei, then regroup to helix from the free-end to form the compact conformations through the middle stages of helix-like coil and helix-like cone, while short chains do not apparently have the above mentioned middle stages. Through simulated annealing, the native conformation of homopolymer chain in our model is found to be helix. We show the relations between specific heat C v (T) and radius of gyration R g (T) as functions of temperature, chain length and the interaction strength, respectively. We find that these two quantities match well and can be combined to interpret the "folding" process of the homopolymer. It is found that the collapse temperature Tθ and the native-like folding temperature T f do not change with the chain length in our model, however the interaction strength affects the values of Tθ and T f .

Information retrieval from X-ray small-angle scattering with polychromatic (`white') synchrotron radiation

1983 ◽  
Vol 16 (1) ◽  
pp. 42-46 ◽  
Author(s):  
O. Glatter ◽  
P. Laggner
Keyword(s):  
Synchrotron Radiation ◽  
Small Angle ◽  
Particle Shape ◽  
Structural Information ◽  
Small Angle Scattering ◽  
Radius Of Gyration ◽  
X Ray ◽  
Angle Scattering ◽  
Slit Length ◽  
Hinge Bending

The possibilities of obtaining structural information from X-ray small-angle scattering experiments with `white' polychromatic synchrotron radiation using line collimation are investigated by numerical simulation. Theoretical scattering curves of geometrical models were smeared with the appropriate wavelength distributions and slit-length functions, afflicted by statistical noise, and then evaluated by identical methods as normally used for experimental data, as described previously [program ITP; Glatter (1977). J. Appl. Cryst. 10, 415–421]. It is shown that even for a wavelength distribution of 50% half width, the information content is not limited to the parameters derived from the central part of the scattering curves, i.e. the radius of gyration and the zero-angle intensity, but also allows qualitative information on particle shape via the distance distribution function p(r). By a `hinge-bending model' consisting of two cylinders linked together at different angles it is demonstrated that changes in the radius of gyration amounting to less than 5% can be detected and quantified, and the qualitative changes in particle shape be reproduced.

scholarly journals Research on the Mechanism of Surfactant Warm Mix Asphalt Additive-Based on Molecular Dynamics Simulation

Coatings ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1303
Author(s):  
Pinhui Zhao ◽  
Mingliang Dong ◽  
Yansheng Yang ◽  
Jingtao Shi ◽  
Junjie Wang ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Shear Stress ◽  
Shear Rate ◽  
Asphalt Binder ◽  
Warm Mix Asphalt ◽  
Dynamics Simulation ◽  
Stone Surface ◽  
Lubricating Film ◽  
Lubrication Performance ◽  
Shear Friction

Warm mix asphalt (WMA) technology can bring certain environmental and technical benefits through reducing the temperature of production, paving, and compaction of mixture asphalt. Recent studies have shown that some WMA additives are able to reduce the temperature by increasing the lubricating properties of asphalt binder.-based on the tribological theory, this paper studied the mechanism of adsorbing and lubricating film of base asphalt and WMA on the surface of stone by molecular dynamics (MD) simulation method, and the effect of surfactant WMA additive on the lubrication performance of the shear friction system of “stone–asphalt–stone”. The model of base asphalt lubricating film, including saturates, aromatics, resin and asphaltene, as well as the model of warm mix asphalt lubricating film containing imidazoline-type surfactant WMA (IMDL WMA) additive molecule, were established. The shear friction system of “stone–asphalt–stone” of base asphalt and warm mix asphalt was built on the basis of an asphalt lubrication film model and representative calcite model. The results show that the addition of IMDL WMA additive can effectively improve the lubricity of asphalt, reduce the shear stress of asphalt lubricating film, and increase the stability of asphalt film. The temperature in the WMA lubricating film rises, while the adsorption energy on the stone surface decreases with the increase of shear rate, indicating that the higher the shear rate is, the more unfavorable it is for the WMA lubricating film to wrap on the stone surface. In addition, the shear stress of the WMA lubricating film decreased with increasing temperature, while the shear stress of the base asphalt lubricating film increased first and then decreased, demonstrating that the compactability of the asphalt mixture did not improve linearly with the increase of temperature.

scholarly journals Flexibility of Short-Strand RNA in Aqueous Solution as Revealed by Molecular Dynamics Simulation: Are A-RNA and A´-RNA Distinct Conformational Structures?

2009 ◽  
Vol 62 (9) ◽  
pp. 1054 ◽  
Author(s):  
Defang Ouyang ◽  
Hong Zhang ◽  
Dirk-Peter Herten ◽  
Harendra S. Parekh ◽  
Sean C. Smith
Keyword(s):  
Molecular Dynamics ◽  
Aqueous Solution ◽  
Structural Information ◽  
Structural Parameters ◽  
Biological Molecules ◽  
Dynamics Simulation ◽  
Viral Gene ◽  
Conformational Structure ◽  
Crystal Forms ◽  
Gene Delivery Vectors

We use molecular dynamics simulations to compare the conformational structure and dynamics of a 21-base pair RNA sequence initially constructed according to the canonical A-RNA and A′-RNA forms in the presence of counterions and explicit water. Our study aims to add a dynamical perspective to the solid-state structural information that has been derived from X-ray data for these two characteristic forms of RNA. Analysis of the three main structural descriptors commonly used to differentiate between the two forms of RNA – namely major groove width, inclination and the number of base pairs in a helical twist – over a 30 ns simulation period reveals a flexible structure in aqueous solution with fluctuations in the values of these structural parameters encompassing the range between the two crystal forms and more. This provides evidence to suggest that the identification of distinct A-RNA and A′-RNA structures, while relevant in the crystalline form, may not be generally relevant in the context of RNA in the aqueous phase. The apparent structural flexibility observed in our simulations is likely to bear ramifications for the interactions of RNA with biological molecules (e.g. proteins) and non-biological molecules (e.g. non-viral gene delivery vectors).

Xanthine oxidase inhibitory activity of Euphorbia peplus L. phenolics

2021 ◽  
Vol 24 ◽  
Author(s):  
Emadeldin M. Kamel ◽  
Noha A. Ahmed ◽  
Ashraf A. El-Bassuony ◽  
Omnia E. Hussein ◽  
Barakat Alrashdi ◽  
...  
Keyword(s):  
Xanthine Oxidase ◽  
Active Site ◽  
Inhibitory Activity ◽  
Drug Binding ◽  
Dynamics Simulation ◽  
Solvent Accessible Surface Area ◽  
Radius Of Gyration ◽  
Euphorbia Peplus

Background: Various phenolics show inhibitory activity towards xanthine oxidase (XO), an enzyme that generates reactive oxygen species which cause oxidative damage. Objective: This study investigated the XO inhibitory activity of Euphorbia peplus phenolics. Methods: The dried powdered aerial parts of E. peplus were extracted, fractioned and phenolics were isolated and identified. The XO inhibitory activity of E. peplus extract (EPE) and the isolated phenolics was investigated in vitro and in vivo. Results: Three phenolics were isolated from the ethyl acetate fraction of E. peplus. All isolated compounds and the EPE showed inhibitory activity towards XO in vitro. In hyperuricemic rats, EPE and the isolated phenolics decreased uric acid and XO activity. Molecular docking showed the binding modes of isolated phenolics with XO, depicting significant interactions with the active site amino acid residues. Molecular dynamics simulation trajectories confirmed the interaction of isolated phenolics with XO by forming hydrogen bonds with the active site residues. Also, the root mean square (RMS) deviations of XO and phenolics-XO complexes achieved equilibrium and fluctuated during the 10 ns MD simulations. The radius of gyration and solvent accessible surface area investigations showed that different systems were stabilized at ≈ 2500 ps. The RMS fluctuations profile depicted that the drug binding site exhibited a rigidity behavior during the simulation. Conclusion: In vitro, in vivo and computational investigations showed the XO inhibitory activity of E. peplus phenolics. These phenolics might represent promising candidates for the development of XO inhibitors.

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