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A microwave-assisted two-steps method was proposed for the facile and fast preparation of silver nanoparticle conductive ink. The nanoparticles in the ink are of multi-sized, which is beneficial to getting higher packing density and better conductivity of the printed/written pattern. The effects of the reaction parameters of microwave and additives on the written pattern resistivity were studied on the basis of scanning electron microscope, X-ray diffraction and surface porosity results. Both of the microwave energy and the addition of PVP as the capping agent were found to be critical for the formation of face-centered cubic silver nanoparticles in the conductive ink. The surface porosity and the pore distribution form were also demonstrated to affect the pattern conductivity. The electrical resistivity or the pattern written with the ink prepared at microwave irradiation time of 90 s was calculated to be 364 μΩ cm. The second step of simple centrifugation process could improve the pattern conductivity effectively. After concentrated the conductive ink for two times, the electrical resistivity of the written pattern reduced from 364 to 77 μΩ cm. The proposed two-steps of microwave combined with centrifugation method is a simple and useful way for the preparation of silver nanoparticle conductive ink that can be used in printed electronics.

A facile one-step microwave approach was employed to synthesize silver nanoparticle (AgNP) conductive ink. The conductive ink contained multi-sized silver nanoparticles. Different particle size distribution can be obtained by adding different amounts of the silver source. The relationship between the conductivity of the direct written pattern using the as-prepared silver conductive ink, the particle packing morphology and the particle size distribution standard deviation was investigated. Among all the samples, conductive ink with a silver weight percentage of 10% can have an optimal electrical resistance of 98 μΩ cm after post-hot/pressure treatment at 100°C and 20 MPa for 10 min. The as-prepared conductive ink is of potential application in printed electronics because the sintering condition of low temperatures is feasible for most kinds of flexible substrate materials.

Silver micro/nanomaterials have attracted a great deal of attention due to their superior physicochemical properties. The atomic migration driven by electromigration or stress-induced migration has been demonstrated to be a promising method for the fabrication of metallic micro-/nanomaterials because of the advantage of simple processing. However, how to realize the controllable fabrication and mass production is still the critical technical problem for the method to be used in large-scale industrial applications. In this paper, the multilayered samples consisted of copper foil substrate, Ti adhesive layer, Ag film, and TiN passivation layer and with arrays of artificial holes on the passivation layer were applied to prepare arrays of Ag micro-particles. For the purpose of controllable fabrication, stress-induced migration experiments combined with finite element simulation were applied to analyze the influence of the passivation layer thickness and the heating temperature on the atom migration and Ag particles growing behavior. And the relationship between size of the fabricated Ag particles and the processing parameters of stress-induced migration experiments were also investigated. As a result, a proper structure size of the multilayered samples and heating temperature were recommended, which can be used for the Ag micro-particles controllable fabrication and mass production.

We perform multiscale simulations based on the coupling of molecular dynamics and lattice-Boltzmann (LB) method to study the electrohydrodynamics of a polyampholyte-grafted spherical nanoparticle. The long-range hydrodynamic interactions are modeled by coupling the movement of particles to a LB fluid. Our results indicate that the net-neutral soft particle moves with a nonzero mobility under applied electric fields. We systematically explore the effects of different parameters, including the chain length, grafting density, electric field, and charge sequence, on the structures of the polymer layer and the electrophoretic mobility of the soft particle. It shows that the mobility of nanoparticles has remarkable dependence on these parameters. We find that the deformation of the polyampholyte chains and the ion distribution play dominant roles in modulating the electrokinetic behavior of the polyampholyte-grafted particle. The enhancement or reduction in the accumulation of counterions around monomers can be attributed to the polymer layer structure and the conformational transition of the chains in the electric field. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017

Coarse-grained molecular dynamics simulations are used to investigate physical deposition behavior of charged amphiphlic diblock copolymers. The effects of solvent selectivity, charge distribution in amphiphlic diblock copolymers, and electric field strength on deposition conformations are studied qualitatively. Flat amphiphilic bilayers, which consist of hydrophilic monolayer and hydrophobic brush, are formed by physical deposition of charged amphiphlic diblock copolymers in nonselective solvents. For physically deposited amphiphlic diblock copolymers in selective solvents, amphiphilic bilayers consist of disc-shaped hydrophilic monolayers and hydrophobic nanospheres are found. This study sheds light on the formation of various amphiphlic diblock copolymer deposition conformations in different solvents and interaction mechanism of different components. Furthermore, the evolution of physical deposition process of charged amphiphlic diblock copolymers layer offers new insight to the controlling of amphiphilic bilayer thickness, hydrophobic nanosphere size, and interface property of depositional amphiphlic diblock copolymers.

In this work, we proposed a microwave method to the fast-and-direct preparation of silver nano-ink. The conductive ink is composed of multi-scaled silver nanoparticles (AgNPs) and a few of silver nanorods (AgNRs) as the conductive components. The differently sized nano-silver can provide high conductivity of the written tracks by affording high packing density. The existed one dimensional nanorods can build bridges between nanoparticles to decrease the silver content while maintaining the conductivity of the written pattern. The as-prepared conductive ink can be stored for 20 days without affecting its usability. The written tracks showed satisfying conductivity with a relatively low silver content of 0.025 mol L−1.

Using molecular dynamics simulations based on explicit-solvent model, we study migration of polymer-modified nanoparticles through nanochannels coated with polymers. The polymers densely grafted on the spherical nanoparticle and the channel surface form spherical polymer brush (SPB) and planar polymer brush (PPB), respectively. The migration of the neutral polymer-modified nanoparticle is driven by electroosmotic flow (EOF). The effects of the electric field strength and the SPB–PPB interaction on polymer conformations and transport dynamics of the SPB are explored. The migration velocity of the SPB reduces as the interaction between the SPB and the PPB increases. For strong SPB–PPB interaction, the directional migration of the SPB can be triggered only after the electric field strength exceeds a critical value. The high EOF velocity forces the center of mass of the spherical nanoparticle to keep near the central region of the channel due to high shear rate close to the brush–fluid interface. Unlike electrophoresis of charged polymer-grafted spherical particles, the SPB adopts a more extended conformation in the plane perpendicular to the EOF direction.

Current-induced changes of surface morphology in printed Ag thin wires were investigated by current stressing tests and numerical simulation. The samples were printed Ag thin wires on a flexible substrate with input and output pads. Different experimentalresults were obtainedthroughchangingthe current density after current supply and the mechanism of those phenomena were investigated by numerical simulations based on the method of atomic flux divergence. Good agreement between the simulations and experimental results was reached. It was found that electromigration was the main factor that caused the change of the surface morphology. The contribution of thermal migration can be ignored, and the Joule heating lead by the supplied current had a very significant accelerating effect on electromigration. Guidelines for effectively changing the Ag thin wire surface through providing predetermined current density was proposed, which were expected to be useful for improving the electrical reliability and lifetime of printed Ag thin wires in flexible electronic devices.

Recently, organic thermoelectric (TE) materials have attracted increasing attention in green energy conversion. However, researches on polymer nanostructured TE materials are still scarce, especially for the 1 D nanostructured polymer materials. In this work, 1D poly(3,4-ethylenedioxythiophene) (PEDOT) nanofiber was synthesized by a self-assembled micellar soft-template approach using anionic surfactant sodium dodecyl sulfate (SDS). Then, a flexible and free-standing PEDOT nanofiber film was prepared through a simple vacuum-assisted filtration method. FE-SEM and TEM characteristics real 1D configuration for all the PEDOT nanostructures. Through adjusting the molar ratio of SDS, oxidizing agent FeCl3 and EDOT monomer (nSDS: nFeCl3: nEDOT), nanofiber with different diameter (10–200 nm) and microtopography can be obtained. Electrical conductivity and Seebeck coefficient measurement indicates that the TE properties of PEDOT can be effectively tuned by adjusting its nanostructure, and a variation range as high as three orders of magnitude for the power factors (10-2–101 μW/mK2) can be realized. Due to a more ordered structure caused by the edge-on packing mode of PEDOT chain, the sample prepared with nSDS: nFeCl3: nEDOT = 30:15:7 shows the highest power factor of 7.2 μW/mK2. This value can be further enhanced to 14.4 μW/mK2 by constructing PEDOT nanofiber/SWCNTs composite.

Small organic multiamine and multihydroxyl molecules have great potential for enhancing overall properties of poly(vinyl alcohol) (PVA) through the cross-linking effect of hydrogen bonds. However, experimentally there remains a remarkable lack of insightful understanding of the cross-linking effect on a molecular level. In the work, we report molecular dynamics simulations to reveal the cross-linking effect of hydrogen bonds of tetraaminopyrimidine (4N-2456) molecules on the structure, chain dynamics and mechanical properties of the PVA matrix. It was found that the addition of 4N-2456 leads to a nonlinear decrease of the free volume of PVA. A critical concentration of 4N-2456, about 5 wt%, was identified, resulting in the formation of 4N-2456 clusters. At this concentration, the PVA chains show the relatively slow mobility, the higher glass transition temperature and elastic modulus. Further increasing the 4N-2456 concentration enhances aggregation, and conversely weakens the interactions of hydrogen bonds between the PVA chains. Our work offers an understanding of how the 4N-2456 molecules influence the PVA chain dynamics and mechanical properties of the PVA matrix on molecular level.

Nanochannels modified with stimuli-responsive copolymer brushes offer a smart nanovalve mechanism. The potential application of these special nanovalves is wide-ranging and includes the areas of drug delivery and signal transduction, as well as molecular machines. In this study, molecular dynamics simulations were performed to study nanovalve systems that use thermo-responsive amphiphilic triblock copolymer brushes grafted onto the surface of the nanochannel. Varying the system temperature facilitated the extension/collapse transition of the copolymer brushes, which resulted in the opening/closing of the nanochannels. The results of the investigation of the effect of the grafting density and the composition of the copolymers on the conformational transition behavior showed that the composition of copolymer has a significant influence on the nanovalve system. A remarkable result is the effectiveness of the use of intermediate or relatively low grafting density in obtaining an ideal controlling effe...

Symmetrical electrical double layer capacitors with ionic liquid potassium hydroxide (KOH)-based poly(acrylic acid) gel polymer electrolytes and activated charcoal electrodes were constructed and characterised. The optimised composition of gel polymer electrolytes exhibits high room temperature ionic conductivity of 0.46 S cm−1 with good mechanical and dimensional stability, which is suitable for their application as electrolyte in electrical double layer capacitors. Analysis shows that the maximum value of capacitance was 0.343 F cm−2, and this value corresponds to an energy density equal to 0.111 J cm−2. Electrical double layer capacitor exhibits large capacitance and high energy density. The results indicate that the gel polymer electrolyte used in our study is promising and is suitable as a solid electrolyte for high-performance all-solid-state electrochemical devices.

Solid Al&ndash, air batteries are a promising power source for potable electronics due to their environmentally friendly qualities and high energy density. However, the solid Al&ndash, air battery suffers from anodic corrosion and it is difficult to achieve a higher specific capacity. Thus, this work aims at suppressing the corrosion of Al anode by adding an electrospun Al2O3 interlayer on to the surface of the anode. The Al2O3 interlayer effectively inhibits the self-corrosion of the Al anode. Further, the effects of the thickness of the Al2O3 film on corrosion behavior were investigated. The results showed that the Al&ndash, air battery with a 4 &mu, m Al2O3 interlayer is more suitable for a low current density discharge, which could be applied for mini-watt devices. With a proper thickness of the Al2O3 interlayer, corrosion of the anode was considerably suppressed without sacrificing the discharge voltage at a low current density. The Al&ndash, m Al2O3 interlayer provided a significantly high capacity (1255 mAh/g at 5 mA/cm2) and an excellent stability. This wo presents a promising approach for fabricating an inhibiting corrosion interlayer for solid Al&ndash, air battery designed for mini-watt devices.

Compared with the traditional fuel vehicle, the pure electric vehicle has excellent characteristics in the emissions and energy use. But its driving ranges are much shorter than the traditional fuel vehicle. It has become a bottleneck problem for the development of electric vehicle. It is difficult to establish the accurate model of driving ranges in the actual working condition. Its main reason is that the influence factors of electric vehicle driving ranges and driving ranges have a non-linear relationship. BP neural network can map the complex non-linear relationship and has strong non-linear fitting ability. Compared the driving ranges of fuzzy control with fuzzy PI control in pure electric vehicle with dual-energy storage system, the results of simulation experiment indicate that the fuzzy PI control can extend the driving rages of electric vehicle. The maximum value of the average error is 2.66% in BP neural network prediction.

Using concentrating photovoltaic (CPV) cells is an effective method for the low-cost photovoltaic conversion. However, higher temperature and non-uniform surface temperature distribution will result in the electrical output decline of CPV cells and shorten their life time. To obtain higher net output power of CPV cells and prolong their life time, we designed a novel multi-layer manifold microchannel cooling system to effectively lower the cell surface temperature and improve the uniformity of surface temperature distribution. Thermal image analysis indicated that the surface temperature difference of the CPV cells was below 6.3 °C. The multi-layer manifold microchannel had a heat transfer coefficient of 8235.84 W/m2 K and its pressure drop was lower than 3 kPa. The results show that the hybrid CPV cells have a satisfactory net output power due to their lower pumping power and the higher electrical output of CPV cells.

We comprehensively illustrate a general process of fitting all-atom molecular mechanics force field (FF) parameters based on quantum mechanical calculations and experimental thermodynamic data. For common organic molecules with free dihedral rotations, this FF format is comprised of the usual bond stretching, angle bending, proper and improper dihedral rotation, and 1–4 scaling pair interactions. An extra format of 1–n scaling pair interaction is introduced when a specific intramolecular rotation is strongly hindered. We detail how the preferred order of fitting all intramolecular FF parameters can be determined by systematically generating characteristic configurations. The intermolecular Van der Waals parameters are initially taken from the literature data but adjusted to obtain a better agreement between the molecular dynamics (MD) simulation results and the experimental observations if necessary. By randomly choosing the molecular configurations from MD simulation and comparing their energies computed from FF parameters and quantum mechanics, the FF parameters can be verified self-consistently. Using an example of a platform chemical 3-hydroxypropionic acid, we detail the comparison between the new fitting parameters and the existing FF parameters. In particular, the introduced systematic approach has been applied to obtain the dihedral angle potential and 1–n scaling pair interaction parameters for 48 organic molecules with different functionality. We suggest that this procedure might be used to obtain better dihedral and 1–n interaction potentials when they are not available in the current widely used FF. © 2014 Wiley Periodicals, Inc.

Aluminum–air (Al–air) battery is one of the most promising candidates for next-generation energy storage systems because of its high capacity and energy density, and abundance. The polyacrylic acid (PAA)-based alkaline gel electrolyte is used in all-solid-state Al–air batteries instead of aqueous electrolytes to prevent leakage. The optimal gel electrolyte exhibits an ionic conductivity of 460 mS cm −1 , which is close to that of aqueous electrolytes. The Al–air battery peak capacity and energy density considering only Al can reach 1166 mAh g −1 -Al and 1230 mWh g −1 -Al, respectively, during constant current discharge. The battery prototype also exhibits a high power density of 91.13 mW cm −2 . For the battery is a laminated structure, area densities of 29.2 mAh cm −2 and 30.8 mWh cm −2 are presented to appraise the performance of the whole cell. A novel design to inhibit anodic corrosion is proposed by separating the Al anode from the gel electrolyte when not in use, thereby effectively maintaining the available capacity of the battery.

The pure electric vehicle with dual-energy storage system is driven under complex driving states. Owing to its nonlinear model, the fuzzy control is usually used in energy distribution. It is difficult for the conventional fuzzy controller without integral part to eliminate the static errors. Its control effect is not satisfactory. The required power minus actual power is the deviation. The self-adaptive fuzzy PI control adjusts the deviation values through tuning the parameters of PI controller in real time. Its control effect is satisfactory. The results of simulation experiment indicate that the self-adaptive fuzzy PI control is more economical than the fuzzy control under the same driving states.

Molecular dynamics simulations are conducted to investigate the suppression of electroosmotic flow by grafting polyampholyte brushes onto two parallel channel walls. The effects of grafting density and charge distribution of polyampholyte brushes on the electroosmotic flow velocity, salt ion distribution, and conformational characteristics of grafted brushes are studied in detail. Simulation results indicate that increasing the grafting density induces a stronger suppression of electroosmotic flow. The flow velocity is significantly influenced by the different charge distributions of polyampholyte brushes. In addition, an important flow phenomenon we have found is that the flow velocity profile shows a valley at the center of the channel. These results reveal that the flow velocity is dependent not only on the conformation of the polyampholyte brushes but also on the anion and cation distributions. The hierarchical distribution of salt ions is caused by the special properties of polyampholyte brushes.

In this paper a hierarchical multiscale model for microfluidic fuel cells with porous electrodes is developed for the first time. An example of the hierarchical multiscale model for all-vanadium microfluidic fuel cells is presented in this study, in which the diffusion coefficient is used as a bridge between the microscale, mesoscale, and macroscale models. Three-level theories are used to describe the microfluidic fuel cells systems. The development of the model in different time and length scales is emphasized. Results from each scale model are compared with the corresponding experimental and other reasonable data in the literature. We demonstrate that the multiscale model is able to predict the characteristics of microfluidic fuel cells more accurately than before. The hierarchical multiscale model can be a potential tool for developing, designing, and optimizing microfluidic fuel cells.

We report an all-atom molecular dynamics study of the structures and dynamics of salty water droplets on a silicon surface under the influence of applied electric field. Our simulation results support ion-specific effects on the elongation dynamics of salty nanodroplets, induced by the field. This feature has not been explored up to now in monovalent salts. Nevertheless, the importance of ion-specific effects is widely confirmed in biological and colloidal systems. In particular, the increase of salt concentration enhances the effect of the nature of ions on the wetting properties of droplets. In the presence of electric field (0.05 V A-1), a complete spreading is implemented in a short time for different droplets at a concentration of 1 M, and the droplet morphology is stable, observed at long time scales. However, a higher salt concentration of 4 M considerably suppresses the spreading process owing to the increase of surface tension. It was found that the NaCl droplet shows deformation oscillations along the external field, but cannot fully wet the substrate surface. By contrast, the CsCl droplet reaches complete elongation rapidly and adopts a steady strip shape. The KCl droplet undergoes frequent transitions between breakup and connection. Additionally, the droplets can be elongated only when the electric field strength exceeds a threshold value. The dipole orientation of interfacial water and the ionic diffusion exhibit ion-specific dependences, but the hydrogen bond network is scarcely disturbed, excluding a concentration-dependent effect.

High-value-added recycling of hazardous waste is a key problem in environmental science and engineering. In previous reports, a hazardous-waste-derived catalyst showed better activity than a catalyst synthesised from pure reagents for the reduction of nitric oxide. The multimetallic nature of hazardous waste was speculated to increase the catalytic activity. In this work, a further investigation was conducted to confirm this speculation. It was found that bimetallic catalysts showed better activity than monometallic ones at 50–200 °C. A bimetallic catalyst removed 75.05% of nitric oxide (990 ppm) at 150 °C, whereas monometallic ones removed only 19.50%. Moreover, the bimetallic catalyst removed 11.46 mmol/g of nitric oxide after 1200 min at 300 °C, which was a much higher concentration than that removed by the monometallic catalyst (2.72 mmol/g). Experimental and simulated Raman spectroscopy revealed that enhanced activity was accompanied by a larger blue shift of the metal band (indicating catalytic centre activity) and a smaller blue shift of the carbon band (indicating reductant stability). In a theoretical calculation, a second metal changed the electron density difference of the catalytic centre and activated the distant reductant, increasing both the low-temperature activity and activity stability. The main result of this study explained the reason bimetallic catalysts outperformed the monometallic ones. Because hazardous waste usually contains bimetallic species, it can be used as a suitable resource for producing effective catalysts.

A new approach for network survivability problem in Internet protocol (IP) over wavelength division multiplexing (WDM) optical network is proposed to enhance the IP layer restorability under physical link failure through logical topology reconfiguration. More specifically, after traffic arrival and departure, reconfiguring the logical topology correspondingly is helpful to minimize the traffic disruption after physical link failure. So, in this paper, this problem is proposed for first time and formulated as an integer linear programming (ILP) problem. And then, two heuristic algorithms are proposed. The performance of proposed algorithms have been evaluated through simulations, and the results show that reconfiguring the logical topology dynamically could achieve more than 20% improvement of the restorability of traffic in IP layer, but with acceptable resource cost.

Molecular dynamics simulations were performed for electro-osmotic flow (EOF) confined in a polyelectrolyte- grafted nanochannel under variable grafting density and nor- mal electric field. With decreasing the value of the normal elec- tric field, the brush undergoes a collapse transition, and the ion distribution is changed significantly. The brush thickness increases on increasing the grafting density at positive and weak negative electric fields, whereas a reduced brush thick- ness is observed at strong negative electric field. Our results further reveal that the flow velocity is not only dependent on conformational transition of the brush but also related to the cation and anion distributions. At low grafting density, the EOF is almost completely quenched at high electric field strength due to strong surface friction between ions and walls. For the case of very dense grafting, the flow velocity is influenced weakly within the brush when varying the grafting density. Additionally, a bidirectional flow occurs at an intermediate electric field. The investigation on fluid flux indicates that the fluid flux is insensitive to the grafting density, when the normal electric field is removed. For nonzero normal electric fields, a significant change in the fluid flux is observed at low grafting densities. V C 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 50: 805-811, 2012

The adsorption and wrapping process of a single flexible comb-like polymer to a single wall nanotube was studied by Molecular Dynamics simulation of a coarse-grained model. We varied the grafting density and length of the side chains, the radius of the nanotube and strength of interaction between the monomers of nanotube and side chains of polymer brush. We investigated the structural and dynamical characters of interactions of the nanotube-polymer composite, such as the effect of Lennard-Jones energy parameter ɛLJ and the nanotube radius on the adsorption behavior and how the wrapping conformation is affected by the structure of the polymer brush. The simulation results indicate that single comb-like polymer with flexible backbone tends to adsorb and wrap around the nanotube, when the interaction energy exceeds a critical value. The monomer adsorption ratio, interaction energy profiles and moment of inertia are obtained. The helical wrapping only occurs when the interaction energy is large enough. Also, the influence of the polymer structure on the conformational behavior is analyzed. This work underscores design elements important for engineering well-defined nanotube-polymer nanocomposite.

A hybrid particle–continuum method is used to study the shear flow confined between two opposing walls, one of which is coated with polymer chains. Molecular dynamics (MD) is used in the particle region near the brush and Navier–Stokes (NS) equations are applied in the remaining region where the continuum assumption holds. The information exchange from the continuum region to the particle region is implemented using the constrained particle dynamics. Both Couette shear flow and oscillatory flow are considered in the present work. The effect of the shear flow on the conformational characteristics of polymer brushes is analyzed. In the overlap region, the velocities obtained from MD simulations are smoothly connected with those from NS equations. Our investigations demonstrate that the hybrid particle–continuum model is valid in exploring the shear behavior of polymer brushes.

Molecular dynamics simulations were done to study the electroosmotic flow (EOF) transport in a nanochannel grafted with polyelectrolytes under the control of an electric field normal to the channel wall. This study first addresses some problems on the interplay between complex EOF and non-equilibrium conformational behavior of polyelectrolyte brushes at a molecular level. We demonstrated that changing the normal electric field has a significant impact on the conformational transition of polyelectrolytes and ion distributions, further leading to some new flow phenomena. The coupling mechanisms of polyelectrolyte chain dynamics and electrohydrodynamics were discussed. A remarkable result obtained is that fluid flux depends nonmonotonically on the normal electric field. Our work provides fundamental understanding of the EOF modulation using polyelectrolyte brushes and guidance for the design of smart nanofluidic channels.

Dissipative particle dynamics (DPD) is used to investigate solvent flow controlled by a cylindrical nanofluidic channel grafted with polymer brushes. Results for monomer and solvent beads density for different solvent quality were obtained, as well as the height and inclination angle of the polymer brushes in Poiseuille flow. The velocity profile and solvent permeability in Poiseuille flow for varying solvent quality were also examined. The polymer brushes expand and inhibit flow under good solvent conditions. However, under poor solvent conditions the chains collapse to open the channel. Additionally, the dependence of the permeability on the grafting density is given. The results indicate that the system is capable of changing the permeability and flow rate drastically upon changing the solvent quality.

We report molecular dynamics simulations on bottle-brush polyelectrolytes end-grafted to a planar surface. For each bottle-brush polyelectrolyte, flexible charged side chains are anchored to one neutral main chain. The effects of the counterion valence and the grafting density on the density profiles and the structural characteristics of the brush were studied in this work. It is found that the electrostatic repulsion between charged monomers in the side chains leads an extended conformation of the brush in a solution containing monovalent counterions, while strong electrostatic binding of multivalent counterions to the side chains has a significant contribution to the collapse of the brush. For the trivalent case, the distribution of end monomers in the main chains becomes broader upon decreasing the grafting density, as compared with the monovalent case. However, the position of the distribution for the monovalent case is relatively insensitive to the change of the grafting density. Additionally, with increased counterion valence, enhanced electrostatic correlation between counterions and charged side chains also weakens the diffusive ability of counterions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011

Using Brownian dynamics simulations, we study the effect of the charge ratio, the surfactant length, and the grafting density on the conformational behavior of the complex formed by the polyelectrolyte brush with oppositely charged surfactants. In our simulations, the polyelectrolyte chains and surfactants are represented by a coarse-grained bead-spring model, and the solvent is treated implicitly. It is found that varying the charge ratio induces different morphologies of surfactant aggregates adsorbed onto the brush. At high charge ratios, the density profiles of surfactant monomers indicate that surfactant aggregates exhibit a layer-by-layer arrangement. The surfactant length has a strong effect on the adsorption behavior of surfactants. The lengthening of surfactant leads to a collapsed brush configuration, but a reswelling of the brush with further increasing the surfactant length is observed. The collapse of the brush is attributed to the enhancement of surfactants binding to polyelectrolyte chains. The reswelling is due to an increase in the volume of adsorbed surfactant aggregates. At the largest grafting density investigated, enhanced excluded volume interactions limit the adsorption of surfactant within the polyelectrolyte brush. We also find that end monomers in polyelectrolyte chains exhibit a bimodal distribution in cases of large surfactant lengths and high charge ratios.