Structure, dynamics and primitive path network of polymer nanocomposites containing spherical nanoparticles

2014 ◽  
Vol 1619 ◽  
Author(s):  
Argyrios Karatrantos ◽  
Nigel Clarke ◽  
Russel J. Composto ◽  
Karen I. Winey
Keyword(s):  
Polymer Nanocomposites ◽  
Volume Fraction ◽  
Md Simulations ◽  
Polymer Structure ◽  
Polymer Chains ◽  
Radius Of Gyration ◽  
Spherical Nanoparticles ◽  
Topological Constraints ◽  
Nanoparticle Radius ◽  
Entangled Polymer

ABSTRACTWe investigate the effect of nanoparticles on polymer structure, polymer dimensions and topological constraints (entanglements) in polymer melts for nanoparticle loading above percolation threshold as high as 40.9% using stochastic molecular dynamics (MD) simulations. We show unambiguously that short polymer chains are not disturbed by the presence of repulsive nanoparticles. In contrast entangled polymer chains can be perturbed by the presence of attractive nanoparticles when the polymer radius of gyration is larger than the nanoparticle radius. They can expand under the presence of attractive nanoparticles even at low nanoparticle loadings of very small nanoparticle size. We observe an increase in the number of entanglements (decrease of Ne with 40.9% volume fraction of nanoparticles dispersed in the polymer matrix) in the nanocomposites as evidenced by larger contour lengths of the primitive paths. Attraction between polymers and nanoparticles affects the entanglements in the nanocomposites and alters the primitive path.

scholarly journals Entanglements in polymer nanocomposites containing spherical nanoparticles

Soft Matter ◽  
2016 ◽  
Vol 12 (9) ◽  
pp. 2567-2574 ◽  
Author(s):  
Argyrios Karatrantos ◽  
Nigel Clarke ◽  
Russell J. Composto ◽  
Karen I. Winey
Keyword(s):  
Molecular Dynamics ◽  
Polymer Nanocomposites ◽  
Polymer Melts ◽  
Md Simulations ◽  
Spherical Nanoparticles ◽  
Pure Polymer ◽  
Topological Constraints ◽  
Polymer Nanoparticle ◽  
Polymer Packing

We investigate the polymer packing around nanoparticles and polymer/nanoparticle topological constraints (entanglements) in nanocomposites containing spherical nanoparticles in comparison to pure polymer melts using molecular dynamics (MD) simulations.

scholarly journals Interface and Interphase in Polymer Nanocomposites with Bare and Core-Shell Gold Nanoparticles

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 541 ◽  
Author(s):  
Albert J. Power ◽  
Ioannis N. Remediakis ◽  
Vagelis Harmandaris
Keyword(s):  
Polymer Nanocomposites ◽  
Polymer Matrix ◽  
Md Simulations ◽  
Polymer Chains ◽  
Core Shell ◽  
Wulff Construction ◽  
Density Profiles ◽  
Au Nps ◽  
Polymeric Chains ◽  
Terminal Dynamics

Metal nanoparticles are used to modify/enhance the properties of a polymer matrix for a broad range of applications in bio-nanotechnology. Here, we study the properties of polymer/gold nanoparticle (NP) nanocomposites through atomistic molecular dynamics, MD, simulations. We probe the structural, conformational and dynamical properties of polymer chains at the vicinity of a gold (Au) NP and a functionalized (core/shell) Au NP, and compare them against the behavior of bulk polyethylene (PE). The bare Au NPs were constructed via a systematic methodology starting from ab-initio calculations and an atomistic Wulff construction algorithm resulting in the crystal shape with the minimum surface energy. For the functionalized NPs the interactions between gold atoms and chemically adsorbed functional groups change their shape. As a model polymer matrix we consider polyethylene of different molecular lengths, from the oligomer to unentangled Rouse like systems. The PE/Au interaction is parametrized via DFT calculations. By computing the different properties the concept of the interface, and the interphase as well, in polymer nanocomposites with metal NPs are critically examined. Results concerning polymer density profiles, bond order parameter, segmental and terminal dynamics show clearly that the size of the interface/interphase, depends on the actual property under study. In addition, the anchored polymeric chains change the behavior/properties, and especially the chain density profile and the dynamics, of the polymer chain at the vicinity of the Au NP.

Development of a simple model to characterize the complex constrained polymer chains in polymer nanocomposites at the interphase of amorphous/semicrystalline ethylene vinyl acetate and nanosheets

2016 ◽  
Vol 51 (2) ◽  
pp. 179-186 ◽  
Author(s):  
Omid Yousefzade ◽  
Hamid Garmabi
Keyword(s):  
Simple Model ◽  
Polymer Nanocomposites ◽  
Vinyl Acetate ◽  
Volume Fraction ◽  
Expanded Graphite ◽  
Ethylene Vinyl Acetate ◽  
Analysis Data ◽  
Polymer Chains ◽  
Polymeric Nanocomposites ◽  
Dispersion State

A simple model was developed to characterize the constrained polymer chains at the interphase of amorphous/semicrystalline polymer nanocomposites based on ethylene vinyl acetate copolymer and some nanosheets such as expanded graphite, graphene and organo-modified montmorillonite. It was found that this method is a useful tool to describe the reinforcement efficiency of nanoparticles. Models were developed using dynamical mechanical thermal analysis data to identify the interphase properties. The volume fraction of constrained polymer chains shows power law relationship with filler content. Since the total volume fraction consists of the confined polymer chains at the surface of nanoparticles and in crystal lamellas, the contribution of nanosheet interphase was evaluated separately. Moreover, the thickness of constructed interphase between polymer chains and nanosheets were predicted using the filler characteristics in the polymer nanocomposites. This implies that the dispersion state of nanofiller in polymeric nanocomposites can be obtained by using this simple model.

The Role of Polymer-particle Interactions on the Viscoelastic Properties of Polymer Nanocomposites

2007 ◽  
Vol 1056 ◽  
Author(s):  
Alireza Sarvestani ◽  
Esmaiel Jabbari
Keyword(s):  
Polymer Nanocomposites ◽  
Volume Fraction ◽  
Molecular Model ◽  
Low Frequency ◽  
Maxwell Model ◽  
Equilibrium Structure ◽  
Polymer Chains ◽  
Spherical Particles ◽  
Filler Concentration ◽  
Adsorbed Polymer

ABSTRACTA molecular model is proposed for the dynamics of polymer chains in dilute polymer solutions containing well-dispersed spherical particles. In the presence of short range energetic affinity between the monomers and filler surface, the equilibrium structure of the adsorbed polymer layer is determined by a scaling theory. The viscoelastic response of the suspension is studied by a Maxwell model. It is shown that the solid-like properties of polymer nanocomposites in low frequency regimes could be attributed to the slowdown of the relaxation process of polymer chains. This process is controlled by the monomer-particle frictional interactions, density of the adsorbed polymer chains on the particles surface (controlled by monomer-particle adsorption energy), and volume fraction of the interfacial layer which can be enhanced by reduction of filler size or increasing the filler concentration.

scholarly journals The Effect of Grafting Density on the Crystallization Behaviors of Polymer Chains Grafted onto One-Dimensional Nanorod

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Tongfan Hao ◽  
Yongqiang Ming ◽  
Shuihua Zhang ◽  
Ding Xu ◽  
Zhiping Zhou ◽  
...  
Keyword(s):  
Polymer Nanocomposites ◽  
Polymer Chains ◽  
Radius Of Gyration ◽  
Mean Square ◽  
Crystalline Morphology ◽  
One Dimensional ◽  
Crystallization Behaviors ◽  
Grafting Density ◽  
Dynamic Monte Carlo ◽  
The Mean

The crystallization behaviors of five polymer chain systems grafted on a nanorod and the corresponding effect of grafting density were investigated by dynamic Monte Carlo simulations. The segment density near the interfacial regions, the number of crystallites, and the mean square radius of gyration (<Rg2>) increase with increasing grafting density, which are beneficial to the enhancement of crystallizability. Meanwhile, the crystalline morphology is greatly influenced by grafting density and polymer-nanorod interaction. For the grafted system with 52 chains, a nanohybrid shish-kebab (NHSK) structure is formed, when the polymer-nanorod interaction (Eb/Ec) is -0.4. For the system with 128 chains, a NHSK structure is formed, when Eb/Ec is -1.0. For the system with 252 chains, NHSK structure cannot be formed. The findings in this work can supply important theoretical reference for the design, preparation, and application of polymer nanocomposites.

Meso-scale Simulations of Poly(N-isopropylacrylamide) Grafted Architectures

2014 ◽  
Vol 1619 ◽  
Author(s):  
Sanket A. Deshmukh ◽  
Ganesh Kamath ◽  
Derrick C. Mancini ◽  
Subramanian K.R.S. Sankaranarayanan ◽  
Wei Jiang
Keyword(s):  
Conformational Dynamics ◽  
Md Simulations ◽  
Polymer Chains ◽  
Effect Of Temperature ◽  
Solution Temperature ◽  
Radius Of Gyration ◽  
Core Particle ◽  
Thermosensitive Polymer ◽  
Critical Solution Temperature ◽  
Different Diameters

ABSTRACTPoly(N-isopropylacrylamide) (PNIPAM) is a thermosensitive polymer that is well-known for its behavior at a lower critical solution temperature (LCST) around 305 K. Below the LCST, PNIPAM is soluble in water, and above this temperature, polymer chains collapse and transform into a globule state. The conformational dynamics of single chains of polymer in a solution is known to be different from those of grafted structures that comprise of an ensemble of such single chains. In this study, we have carried out MD simulations of a mesoscopic nanostructure of PNIPAM polymer chains consisting of 60 monomer units grafted onto gold nanoparticles of different diameters, to study the effect of temperature and core particle size on the polymer conformations. Additionally, we have also studied the effect of grafting density on the coil-to-globule transition exhibited by PNIPAM through the LCST. The systems investigated consisted of ∼3 and ∼6 million atoms. Simulations were carried out below and above the LCST of PNIPAM, at 275K and 325K. Simulation trajectories were analyzed for radius of gyration of PNIPAM chains.

Effect of Methanol/Water Mixtures on the Lower Critical Solution Temperature of Poly(N-isopropylacrylamide)

2014 ◽  
Vol 1622 ◽  
pp. 25-30 ◽  
Author(s):  
Sanket A. Deshmukh ◽  
Ganesh Kamath ◽  
Derrick C. Mancini ◽  
Subramanian K.R.S. Sankaranarayanan
Keyword(s):  
Mole Fraction ◽  
Lower Critical Solution Temperature ◽  
Md Simulations ◽  
Polymer Chains ◽  
Solution Temperature ◽  
Radius Of Gyration ◽  
Solvation Dynamics ◽  
Water Mixture ◽  
Critical Solution Temperature ◽  
Lcst Behavior

ABSTRACTPoly(N-isopropylacrylamide) (PNIPAM) is a thermo-sensitive polymer that exhibits a lower critical solution temperature (LCST) around 305 K. Below the LCST, PNIPAM is soluble in water and above this temperature polymer chains collapse prior to aggregation. In the presence of methanol, electron paramagnetic resonance (EPR) spectroscopy suggests that, LCST of PNIPAM is depressed up to certain mole fraction of methanol (0.35 mole fraction) and it is speculated that addition of methanol affects the PNIPAM-water interactions. Above 0.35 mole fraction of methanol, LCST gets elevated to temperatures above ∼305 K (32°C) and cannot be detected up to 373 K (100 °C). The atomistic origin of this co-solvency effect on the LCST behavior is not completely understood. In the present study, we have used molecular dynamics (MD) simulations to investigate the effect of methanol-water mixtures on conformational transitions and the LCST of PNIPAM. We employ two different force fields i.e. polymer consistent force-field (PCFF) and CHARMM to study solvation dynamics and the PNIPAM LCST phase transition in various methanol-water mixture compositions (0.018, 0.09, 0.27, 0.5, and 0.98 mole fractions). Simulations are conducted at fully atomistic level for three different temperatures (260, 278, and 310 K) and radius of gyration (Rg) of PNIPAM chains was computed for determination of LCST behavior of PNIPAM.

Effect of Ionic Strength on the Aggregation Propensity of Aβ1-42 Peptide: An In-silico Study

2020 ◽  
Vol 14 (3) ◽  
pp. 216-226
Author(s):  
Priyanka Borah ◽  
Venkata S.K. Mattaparthi
Keyword(s):  
Diffusion Coefficient ◽  
Ionic Strength ◽  
Marked Effect ◽  
Computational Study ◽  
Conformational Dynamics ◽  
Rapid Change ◽  
Md Simulations ◽  
Radius Of Gyration ◽  
Aggregation Propensity ◽  
In Silico Study

Background: Aggregation of misfolded proteins under stress conditions in the cell might lead to several neurodegenerative disorders. Amyloid-beta (Aβ1-42) peptide, the causative agent of Alzheimer’s disease, has the propensity to fold into β-sheets under stress, forming aggregated amyloid plaques. This is influenced by factors such as pH, temperature, metal ions, mutation of residues, and ionic strength of the solution. There are several studies that have highlighted the importance of ionic strength in affecting the folding and aggregation propensity of Aβ1-42 peptide. Objective: To understand the effect of ionic strength of the solution on the aggregation propensity of Aβ1-42 peptide, using computational approaches. Materials and Methods: In this study, Molecular Dynamics (MD) simulations were performed on Aβ1-42 peptide monomer placed in (i) 0 M, (ii) 0.15 M, and (iii) 0.30 M concentration of NaCl solution. To prepare the input files for the MD simulations, we have used the Amberff99SB force field. The conformational dynamics of Aβ1-42 peptide monomer in different ionic strengths of the solutions were illustrated from the analysis of the corresponding MD trajectory using the CPPtraj tool. Results: From the MD trajectory analysis, we observe that with an increase in the ionic strength of the solution, Aβ1-42 peptide monomer shows a lesser tendency to undergo aggregation. From RMSD and SASA analysis, we noticed that Aβ1-42 peptide monomer undergoes a rapid change in conformation with an increase in the ionic strength of the solution. In addition, from the radius of gyration (Rg) analysis, we observed Aβ1-42 peptide monomer to be more compact at moderate ionic strength of the solution. Aβ1-42 peptide was also found to hold its helical secondary structure at moderate and higher ionic strengths of the solution. The diffusion coefficient of Aβ1-42 peptide monomer was also found to vary with the ionic strength of the solution. We observed a relatively higher diffusion coefficient value for Aβ1-42 peptide at moderate ionic strength of the solution. Conclusion: Our findings from this computational study highlight the marked effect of ionic strength of the solution on the conformational dynamics and aggregation propensity of Aβ1-42 peptide monomer.

scholarly journals Recent Advances in the Synthesis of Polymer-Grafted Low-K and High-K Nanoparticles for Dielectric and Electronic Applications

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2942
Author(s):  
Bhausaheb V. Tawade ◽  
Ikeoluwa E. Apata ◽  
Nihar Pradhan ◽  
Alamgir Karim ◽  
Dharmaraj Raghavan
Keyword(s):  
Energy Density ◽  
Polymer Nanocomposites ◽  
High Performance ◽  
Breakdown Strength ◽  
Polymer Nanocomposite ◽  
High Energy ◽  
Polymer Chains ◽  
High Energy Density ◽  
Grafted Nanoparticles ◽  
Grafting From

The synthesis of polymer-grafted nanoparticles (PGNPs) or hairy nanoparticles (HNPs) by tethering of polymer chains to the surface of nanoparticles is an important technique to obtain nanostructured hybrid materials that have been widely used in the formulation of advanced polymer nanocomposites. Ceramic-based polymer nanocomposites integrate key attributes of polymer and ceramic nanomaterial to improve the dielectric properties such as breakdown strength, energy density and dielectric loss. This review describes the ”grafting from” and ”grafting to” approaches commonly adopted to graft polymer chains on NPs pertaining to nano-dielectrics. The article also covers various surface initiated controlled radical polymerization techniques, along with templated approaches for grafting of polymer chains onto SiO2, TiO2, BaTiO3, and Al2O3 nanomaterials. As a look towards applications, an outlook on high-performance polymer nanocomposite capacitors for the design of high energy density pulsed power thin-film capacitors is also presented.

scholarly journals Conformational Ensembles by NMR and MD Simulations in Model Heptapeptides with Select Tri-Peptide Motifs

2021 ◽  
Vol 22 (3) ◽  
pp. 1364
Author(s):  
V. V. Krishnan ◽  
Timothy Bentley ◽  
Alina Xiong ◽  
Kalyani Maitra
Keyword(s):  
Principal Component ◽  
Md Simulations ◽  
Conformational Space ◽  
Random Coil ◽  
Radius Of Gyration ◽  
Small Peptides ◽  
Conformational Ensembles ◽  
Solution State ◽  
Peptide Motifs ◽  
Explicit Solvent

Both nuclear magnetic resonance (NMR) and molecular dynamics (MD) simulations are routinely used in understanding the conformational space sampled by peptides in the solution state. To investigate the role of single-residue change in the ensemble of conformations sampled by a set of heptapeptides, AEVXEVG with X = L, F, A, or G, comprehensive NMR, and MD simulations were performed. The rationale for selecting the particular model peptides is based on the high variability in the occurrence of tri-peptide E*L between the transmembrane β-barrel (TMB) than in globular proteins. The ensemble of conformations sampled by E*L was compared between the three sets of ensembles derived from NMR spectroscopy, MD simulations with explicit solvent, and the random coil conformations. In addition to the estimation of global determinants such as the radius of gyration of a large sample of structures, the ensembles were analyzed using principal component analysis (PCA). In general, the results suggest that the -EVL- peptide indeed adopts a conformational preference that is distinctly different not only from a random distribution but also from other peptides studied here. The relatively straightforward approach presented herein could help understand the conformational preferences of small peptides in the solution state.

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