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Book ChapterDOI

Multiscale Molecular Modeling of Clay–Polymer Nanocomposites

TL;DR: In this paper, a multiscale molecular simulation protocol for predicting morphologies and properties of nanostructured polymer systems is presented, and applied to three examples of industrial relevance.
Abstract: A current challenge of physical, chemical, and engineering sciences is to develop computational tools for predicting the structure and properties of complex materials from the knowledge of a few input parameters. Accordingly, in this chapter, we present a multiscale molecular simulation protocol for predicting morphologies and properties of nanostructured polymer systems, and we apply it to three examples of industrial relevance. In this chapter, we will discuss a new strategy of study of many polymer–clay nanocomposites using multiscale molecular modeling (atomistic, mesoscale, and finite element calculations) for the prediction of morphological, thermophysical, mechanical, and transport properties, as well as for the development of theories and models for polymer nanocomposites.
Citations
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01 Jan 2006
TL;DR: In this article, a hierarchical procedure for bridging the gap between atomistic and macroscopic modeling passing through mesoscopic simulations is presented, and examples of applications of multiscale procedures to polymer-organoclay nanocomposites are discussed.
Abstract: Atomistic-based simulations such as molecular mechanics (MM), molecular dynamics (MD), and Monte Carlo-based methods (MC) have come into wide use for materials design. Using these atomistic simulation tools, one can analyze molecular structure on the scale of 0.1–10 nm. Although molecular structures can be studied easily and extensively by these atom-based simulations, it is less realistic to predict structures defined on the scale of 100–1000 nm with these methods. For the morphology on these scales, mesoscopic modeling techniques such as the dynamic mean field density functional theory (Mesodyn) and dissipative particle dynamics (DPD) are now available as effective simulation tools. Furthermore, it is possible to transfer the simulated mesoscopic structure to finite element modeling tools (FEM) for calculating macroscopic properties for a given system of interest. In this paper, we present a hierarchical procedure for bridging the gap between atomistic and macroscopic modeling passing through mesoscopic simulations. In particular, we will discuss the concept of multiscale modeling, and present examples of applications of multiscale procedures to polymer–organoclay nanocomposites. Examples of application of multiscale modeling to immiscible polymer blends and polymer–carbon nanotubes systems will also be presented. © 2006 Elsevier B.V. All rights reserved.

103 citations

01 Jan 2003
TL;DR: In this paper, molecular simulation techniques are used to explore and characterize the atomic scale structure, and to predict binding energies and basal spacing of polymer/clay nanocomposites based on polypropylene (PP) and maleated polypropylon (PPMA), montmorillonite (MMT), and different alkylammonium ions (quats) as surfactants.
Abstract: Molecular simulation techniques are used to explore and characterize the atomic scale structure, and to predict binding energies and basal spacing of polymer/clay nanocomposites based on polypropylene (PP) and maleated polypropylene (PPMA), montmorillonite (MMT), and different alkylammonium ions (quats) as surfactants. Our evidences suggest that shorter hydrocarbonic chains are more effective in producing favorable binding energies with respect to longer ones, and the substitutions of hydrogen atoms with polar groups on the quaternary ammonium salt (quat) generally results in greater interaction between quat and both polymer and clay. Under the hypothesis, that montmorillonite platelets are uniformly dispersed in a polymer matrix, the modified polypropylene yields higher interfacial strength with clay than neat polypropylene. The use of neat PP and quats with higher molecular volume offer the higher values of the basal spacing and thus, in principle, they should be more effective in the exfoliation process.

87 citations

Journal Article
TL;DR: In this article, two varieties of clay (Cloisite and Laponite RD) have been used to prepare TPU-based nanocomposites, and a detailed investigation of the thermal, morphological, and rheological behavior reflects the affinity of Cloisite towards the soft segment.
Abstract: Thermoplastic polyurethane (TPU) is a versatile polymer exhibiting many engineering applications. In this article, two varieties of clay (Cloisite and Laponite RD) have been used to prepare TPU-based nanocomposites. They differ in, chemical composition, hydrophobicity, aggregation tendency, and dispersibility in a particular solvent. A detailed investigation of the thermal, morphological, and rheological behavior reflects the affinity of Cloisite towards the soft segment, whereas it is the hard segment for modified Laponite. The maximum improvement in onset degradation temperature has been observed to be 17.5 and 8.3 °C for Cloisite and Laponite, respectively. Five percent Cloisite-filled sample shows optimum storage modulus in the glassy region where as it is the 10% filled sample at the rubbery region. However, the trend remains indifferent both in rubbery and glassy regions for Laponite, and properties have been found optimum for 3% filled sample. To explore the behavior in the terminal and flow regions, dynamic rheological experiments were performed in low shear rate. Variation in dynamic rheological properties can be explained well on the basis of the combination of partly exfoliated, intercalated, and aggregated structures of the nano clay inside the TPU matrix, depending on their nature and preferential association with different segments.

37 citations

Journal ArticleDOI
TL;DR: In this article, the accelerated photo-oxidation under UV light of polyimide (PI) films filled with functionalized vermiculite (VMT) clay (i.e., 1 − 7 wt %) were examined from 0 to 600h.
Abstract: Herein, accelerated photo-oxidation under UV light of polyimide (PI) films filled with functionalized vermiculite (VMT) clay (i.e., 1–7 wt %.) were examined from 0 to 600 h. Thick films (⁓ 60 µm) were fabricated and exposed to accelerated UV light (λ > 295 nm). The as-synthesized PI-reinforced clay nanocomposites were examined by Fourier transform infrared (FT-IR), scanning surface micrograph (SEM), yellowing index, and thermogravimetric analysis (TGA), respectively. The surface morphology examined by SEM exhibits well exfoliation of VMT clay in the PI matrix. The change in internal chemistry on a higher temperature and clay composition is found to be the result of the aggregation of clay. The yellowing index determined by UV–Vis spectroscopy followed a similar tendency as the carbonyl index. TGA analysis revealed good heat resistance in clay-based PI due to the lower thermal expansion of clay reinforcement. Overall, the data clearly showed a better photo-stability of the developed clay/PI composites over the pristine polymer. It is concluded that clay-based PI could be a better alternative in applications requiring harsh conditions, as clay has improved the oxidative, thermal, and insulation properties of the PI matrix.

8 citations

Journal ArticleDOI
08 Jan 2020
TL;DR: In this paper, the structural properties of high molecular weight polyisoprene (PI) in contact with graphite were analyzed using a simple and efficient way to optimize a chemically specific bead-and-spring model for polymer/surface systems.
Abstract: Using a simple and efficient way to optimize a chemically specific bead-and-spring model for polymer/surface systems, we analyze the structural properties of high molecular weight polyisoprene (PI) in contact with graphite. We find that in the vicinity of the graphite the adsorbed PI chains assume a pancake structure and are highly packed and highly entangled. The addition of plasticizers even with moderate surface affinity guarantees an almost complete surface coverage and forces the polymer chains to detach from the surface and to become less entangled. The softening effect of the plasticizers is observed also in bulk when they are added to the system but are not adsorbed on the surface. Finally, we show that the definition of the thickness of the interface is not unambiguous but depends on the observable used to characterized the melt: it is function of the polymer molecular weight if defined looking at the chain conformation, but it becomes independent of the polymer chain length if defined looking at...

8 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a method is described to realize coupling to an external bath with constant temperature or pressure with adjustable time constants for the coupling, which can be easily extendable to other variables and to gradients, and can be applied also to polyatomic molecules involving internal constraints.
Abstract: In molecular dynamics (MD) simulations the need often arises to maintain such parameters as temperature or pressure rather than energy and volume, or to impose gradients for studying transport properties in nonequilibrium MD A method is described to realize coupling to an external bath with constant temperature or pressure with adjustable time constants for the coupling The method is easily extendable to other variables and to gradients, and can be applied also to polyatomic molecules involving internal constraints The influence of coupling time constants on dynamical variables is evaluated A leap‐frog algorithm is presented for the general case involving constraints with coupling to both a constant temperature and a constant pressure bath

25,256 citations

Journal ArticleDOI
TL;DR: An overview of the lattice Boltzmann method, a parallel and efficient algorithm for simulating single-phase and multiphase fluid flows and for incorporating additional physical complexities, is presented.
Abstract: We present an overview of the lattice Boltzmann method (LBM), a parallel and efficient algorithm for simulating single-phase and multiphase fluid flows and for incorporating additional physical complexities. The LBM is especially useful for modeling complicated boundary conditions and multiphase interfaces. Recent extensions of this method are described, including simulations of fluid turbulence, suspension flows, and reaction diffusion systems.

6,565 citations

Journal ArticleDOI
TL;DR: In this paper, a general all-atom force field for atomistic simulation of common organic molecules, inorganic small molecules, and polymers was developed using state-of-the-art ab initio and empirical parametrization techniques.
Abstract: A general all-atom force field for atomistic simulation of common organic molecules, inorganic small molecules, and polymers was developed using state-of-the-art ab initio and empirical parametrization techniques. The valence parameters and atomic partial charges were derived by fitting to ab initio data, and the van der Waals (vdW) parameters were derived by conducting MD simulations of molecular liquids and fitting the simulated cohesive energies and equilibrium densities to experimental data. The combined parametrization procedure significantly improves the quality of a general force field. Validation studies based on large number of isolated molecules, molecular liquids and molecular crystals, representing 28 molecular classes, show that the present force field enables accurate and simultaneous prediction of structural, conformational, vibrational, and thermophysical properties for a broad range of molecules in isolation and in condensed phases. Detailed results of the parametrization and validation f...

4,722 citations

Journal ArticleDOI
TL;DR: In this article, a review of dissipative particle dynamics (DPD) as a mesoscopic simulation method is presented, and a link between these parameters and χ-parameters in Flory-Huggins-type models is made.
Abstract: We critically review dissipative particle dynamics (DPD) as a mesoscopic simulation method. We have established useful parameter ranges for simulations, and have made a link between these parameters and χ-parameters in Flory-Huggins-type models. This is possible because the equation of state of the DPD fluid is essentially quadratic in density. This link opens the way to do large scale simulations, effectively describing millions of atoms, by firstly performing simulations of molecular fragments retaining all atomistic details to derive χ-parameters, then secondly using these results as input to a DPD simulation to study the formation of micelles, networks, mesophases and so forth. As an example application, we have calculated the interfacial tension σ between homopolymer melts as a function of χ and N and have found a universal scaling collapse when σ/ρkBTχ0.4 is plotted against χN for N>1. We also discuss the use of DPD to simulate the dynamics of mesoscopic systems, and indicate a possible problem with...

3,837 citations

Journal ArticleDOI
01 Jun 1992-EPL
Abstract: We present a novel method for simulating hydrodynamic phenomena. This particle-based method combines features from molecular dynamics and lattice-gas automata. It is shown theoretically as well as in simulations that a quantitative description of isothermal Navier-Stokes flow is obtained with relatively few particles. Computationally, the method is much faster than molecular dynamics, and the at same time it is much more flexible than lattice-gas automata schemes.

3,338 citations