A hierarchical procedure bridging the gap between atomistic and mesoscopic simulation for polymer-clay nanocomposite (PCN) design is presented. The dissipative particle dynamics (DPD) is adopted as the mesoscopic simulation technique, and the interaction parameters of the mesoscopic model are estimated by mapping the corresponding energy values obtained from atomistic molecular dynamics (MD) simulations. The predicted structure of the nylon 6 PCN system considered is in excellent agreement with previous experimental and atomistic simulation results. 相似文献
Hybrid polymeric micelles self-assembled from a mixture containing poly(γ-benzyl-L-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) block copolymer and gold nanoparticles (AuNPs) were prepared. The effect of AuNPs on the self-assembly behavior of PBLG-b-PEG was studied both experimentally by transmission electron microscopy, scanning electron microscopy, and laser light scattering and computationally using dissipative particle dynamics (DPD) simulations. It was found that, the pure PBLG-b-PEG block copolymer self-assembles into long cylindrical micelles. By introducing AuNPs to the stock block copolymer solution, the formed aggregate morphology transforms to spherical micelles. The DPD simulation results well reproduced the morphological transformations observed in the experiments. And the simulation revealed that the main reason for the aggregate morphology transformation is the breakage of ordered packing of PBLG rods in micelle core by the added nanoparticles. Moreover, from the DPD simulations, the distribution information on nanoparticles was obtained. The nanoparticles were found to prefer to locate near the core/shell interface as well as in the core center of the micelles. The combination of experimental and simulation methods lead to a comprehensive understanding of such a complex self-assembly system. 相似文献
The formation of microemulsions in the presence of cyclohexane, Triton X-100, n-butanol, water, and task-special ionic liquid (TSIL) (1-2-aminoethyl-3-butylimidazolium tetrafluoroborate) was studied at 25°C. The phase behavior of this ternary system was investigated. Three subregions (namely, water-in-oil phase, bicontinuous phase, and oil-in-water phase) were identified in the single-phase region by dynamic light scattering (DLS) technique and electrical conductivity measurement. Microstructures of microemulsions with different water contents have been predicted by using dissipative particle dynamics (DPD) simulation. It was found that the DPD simulations successfully reproduce the experimental results in the article. The location of TSIL in the microemulsions was predicted by DPD simulation further. The result indicates that TSIL is more easy to locate in the surfactant and cosurfactant layer and has amphiphilicity, which provides us new insights into the potential applications of TSIL-based microemulsions in separation and new nano-scale material preparation because of the interaction of TSIL with some special components at the interface of oil and water. 相似文献
Multicompartment micelles are a new class of nanomaterials that may find wide applications in the fields of drug delivery, nanotechnology and catalysis. Due to their structural complexity, as well as the wide parameter space to explore, experimental investigations are a difficult task, to which molecular simulation may contribute greatly. In this paper, the application of the dissipative particle dynamics simulation technique to the understanding of multicompartment micelles is introduced, illustrating that DPD is a powerful tool for identifying new morphologies by varying block length, block ratio and solvent quality in a systematic way. The formation process of multicompartment micelles, as well as shear effects and the self-assembly of nanoparticle mixtures in multicompartment micelles, can also be studied well by DPD simulation. The present work shows that DPD, as well as other simulation techniques and theories, can complement experiments greatly, not only in exploring properties in a wider parameter space, but also by giving a preview of phenomena prior to experiments. DPD, as a mesoscopic dynamic simulation technique, is particularly useful for understanding the dynamic processes of multicompartment micelles at a microscopic level.
Abstract A simple model, i.e., sodium bis(2‐ethylhexyl) sulfosuccinate [Aerosol OT (AOT)] represented by one‐head and two‐tail beads tied together by a harmonic spring and water or isooctane by one bead, was put forward via dissipative particle dynamics (DPD) simulation method. According to the experimental AOT/water/isooctane system, the aggregates of simulated reverse micelle can be obtained in the three‐dimensional cell. Three types of water morphology, such as bound water, trapped water, and bulky water, were distinguished using the water isodensity slice in DPD simulation. The IR spectra experiment also showed three types of water in the same system. One conclusion is that DPD simulation can be considered as an adjunct to experiments and provide other valuable information for the experiment. 相似文献
Dissipative particle dynamics (DPD) is a mesoscopic simulation method for studying hydrodynamic behavior of complex fluids. Ideally, a mesoscopic model should correctly represent the thermodynamic and hydrodynamic properties of a real system beyond certain length and time scales. Traditionally defined DPD quite successfully mimics hydrodynamics but is not flexible enough to accurately describe the thermodynamics of a real system. The so-called multibody DPD (MDPD) is a pragmatic extension of the classical DPD that allows one to prescribe the thermodynamic behavior of a system with only a small performance impact. In an earlier paper [S. Y. Trofimov, E. L. F. Nies, and M. A. J. Michels, J. Chem. Phys. 117, 9383 (2002)] we much improved the accuracy of the MDPD model for strongly nonideal systems, which are of most practical interest. The ability to correctly reproduce the equation of state of realistic systems in turn makes simulations at constant pressure sensible and useful. This situation of constant-pressure conditions is very common in experimental studies of (soft) condensed matter but has so far remained unexplored with the traditional DPD. Here, as a proof of concept, we integrate a modified version of the Andersen barostat into our improved MDPD model and make an evaluation of the performance of the new model on a set of single- and multicomponent systems. The modification of the barostat suppresses the "unphysical" volume oscillations after a sudden pressure change and simplifies the equilibration of the system. 相似文献
Lowe-Andersen (LA) temperature controlling method [C. P. Lowe, Europhys. Lett. 47, 145 (1999)] is applied in a series of mesoscopic polymer simulations to test its validity and efficiency. The method is an alternative for dissipative particle dynamics simulation (DPD) technique which is also Galilean invariant. It shows excellent temperature control and gives correct radial distribution function as that from DPD simulation. The efficiency of LA method is compared with other typical DPD integration schemes and is proved to be moderately efficient. Moreover, we apply this approach to diblock copolymer microphase separation simulations. With LA method, we are able to reproduce all the results from the conventional DPD simulations. The calculated structure factors of the microphases are consistent with the experiments. We also study the microphase evolution dynamics with increasing chiN and find that the bath collision frequency Gamma does not affect the order of appearing phases. Although the thermostat does not affect the surface tension, the order-disorder transition (ODT) is somewhat sensitive to the values of Gamma, i.e., the ODT is nonmonotonic with increasing Gamma. The dynamic scaling law is also tested, showing that the relation obeys the Rouse theory with various Gamma. 相似文献
We present a mesoscale simulation technique, called the reaction ensemble dissipative particle dynamics (RxDPD) method, for studying reaction equilibrium of polymer systems. The RxDPD method combines elements of dissipative particle dynamics (DPD) and reaction ensemble Monte Carlo (RxMC), allowing for the determination of both static and dynamical properties of a polymer system. The RxDPD method is demonstrated by considering several simple polydispersed homopolymer systems. RxDPD can be used to predict the polydispersity due to various effects, including solvents, additives, temperature, pressure, shear, and confinement. Extensions of the method to other polymer systems are straightforward, including grafted, cross-linked polymers, and block copolymers. To simulate polydispersity, the system contains full polymer chains and a single fractional polymer chain, i.e., a polymer chain with a single fractional DPD particle. The fractional particle is coupled to the system via a coupling parameter that varies between zero (no interaction between the fractional particle and the other particles in the system) and one (full interaction between the fractional particle and the other particles in the system). The time evolution of the system is governed by the DPD equations of motion, accompanied by changes in the coupling parameter. The coupling-parameter changes are either accepted with a probability derived from the grand canonical partition function or governed by an equation of motion derived from the extended Lagrangian. The coupling-parameter changes mimic forward and reverse reaction steps, as in RxMC simulations. 相似文献