The interaction of partially hydrolyzed polyacrylamide (HPAM) with dodecyl-oxypropyl-ß-hydroxyl trimethyl-ammonium bromide (C 12NBr) and nonyl-phenyl-oxypropyl-ß-hydroxyl trimethyl-ammonium bromide (C 9phNBr) in the solution was investigated by the Dissipative Particle Dynamics (DPD) method. The calculated interaction parameters between HPAM and C 12NBr or C 9phNBr showed that C 12NBr is most likely to form polymer/surfactant complex with HPAM in contrast to C 9phNBr. The experiment of binding isotherm was used to validate the DPD results via surfactant-selective electrode and equilibrium dialysis method. In DPD method, the mean square end-to-end distance 2> of polymer chain firstly increased, then reduced, and finally increased again. In addition, some polymer/surfactant complexes were also shown. One conclusion is that mesoscopic simulation can be considered as an adjunct to experiments and provide otherwise inaccessible (or not easily accessible) information in the experiment. 相似文献
There is a growing interest in the study of surfactant self-assemble in oil/water/surfactant system because of their applications not only in traditional colloid chemistry but in analytical, synthetic, and medicinal chemistry as well1,2. In these systems, one of the most commonly studied surfactants which can form reverse micelles is sodium bis(2-ethylhexyl) sulfosuccinate, i.e. Aerosol OT (AOT)3. The properties of the AOT reverse micelles have been discussed by some experimental methods4… 相似文献
The authors analyzed extensively the dynamics of polymer chains in solutions simulated with dissipative particle dynamics (DPD), with a special focus on the potential influence of a low Schmidt number of a typical DPD fluid on the simulated polymer dynamics. It has been argued that a low Schmidt number in a DPD fluid can lead to underdevelopment of the hydrodynamic interaction in polymer solutions. The authors' analyses reveal that equilibrium polymer dynamics in dilute solution, under typical DPD simulation conditions, obey the Zimm [J. Chem. Phys. 24, 269 (1956)] model very well. With a further reduction in the Schmidt number, a deviation from the Zimm model to the Rouse model is observed. This implies that the hydrodynamic interaction between monomers is reasonably developed under typical conditions of a DPD simulation. Only when the Schmidt number is further reduced, the hydrodynamic interaction within the chains becomes underdeveloped. The screening of the hydrodynamic interaction and the excluded volume interaction as the polymer volume fraction is increased are well reproduced by the DPD simulations. The use of soft interaction between polymer beads and a low Schmidt number do not produce noticeable problems for the simulated dynamics at high concentrations, except for the entanglement effect which is not captured in the simulations. 相似文献
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
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
The influence of salt and shear force on the stability of the micelle formed by surfactants and polymer are studied using dissipative particle dynamics (DPD) simulation method. The research system mainly includes four types of surfactants with different hydrophilic/hydrophobic chain branches and two kinds of polymers with hydrophilic/hydrophobic properties, respectively. The stability of the micelle is studied based on the analyses of the density peak and root mean square (RMS) of polymer chain under different salt and shear force. The calculated results show that the density peak reduced and RMS increased for all surfactants with the salt concentration and shear force increasing, and then indicate that the micelle has a certain degree of deformation. Whereas, the surfactant chain branch has important influence on the deformation extent of the micelle. For hydrophobic polymer, surfactants containing hydrophobic chain branch (T2H2T2) are beneficial to the stability of the micelle. On the contrary, for hydrophilic polymer, the micelle formed by surfactants with stronger hydrophilic nature such as the hydrophilic groups located in the both ends of the molecule (H1T4H1) have the best salt and shear resistance. The results have certain theoretical significance and can provide theoretical support for the selection of surfactants and polymers in practical application. 相似文献
Dissipative particle dynamics (DPD), a mesoscopic simulation approach, has been used to investigate the chain length effect on the structural property of the immiscible polyethylene (PE)/poly(L-lactide) (PLLA) polymer in a polymer blend and in a system with their diblock copolymer. In this work, the interaction parameter in DPD simulation, related to the Flory-Huggins interaction parameter chi, is estimated by the calculation of mixing energy for each pair of components in molecular dynamics simulation. The immiscibility property of PE and PLLA polymers induces the phase separation and exhibits different architectures at different volume fractions. In order to observe the structural property, the radius of gyration is used to observe the detailed arrangement of the polymer chains. It shows that the structure arrangement of a polymer chain is dependent on the phase structure and has a significantly different structural arrangement character for the very short chains in the homopolymer and copolymers. The chain length effect on the degree of stretching or extension of polymers has also been observed. As the chain length increases, the chain exhibits more stretching behavior at lamellae, perforated lamellae, and cylindrical configurations, whereas the chain exhibits a similar degree of stretching or extension at the cluster configuration. 相似文献
Summary: The structure of polymer brushes is investigated by dissipative particle dynamics (DPD) simulations that include explicit solvent particles. With an appropriate choice of the DPD interaction parameters , we obtain good agreement with previous molecular dynamics (MD) results where the good solvent behavior has been modeled by an effective Lennard–Jones potential. The present results confirm that DPD simulation techniques can be applied for large length scale simulations of polymer brushes. A relation between the different length scales and is established.
