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Hypothesis Delivery of multiple payloads using the same micelle is of significance to achieve multifunctional or synergistic effects. The interacting distribution of different payloads in micelles is expected to influence the loading stability and capacity. It is highly desirable to explore how intermolecular interactions affect the joint distribution of multi-payloads. Experiments Dissipative Particle Dynamics simulations were performed to probe the loading of three payloads: decane with a linear carbon chain, butylbenzene with an aromatic ring connected to carbon chain, and naphthalene with double aromatic rings, within poly(β-amino ester)-b-poly(ethylene glycol) micelles. Properties of core-shell micelles, e.g., morphological evolution, radial density distribution, mean square displacement, and contact statistics, were analyzed to reveal payloads loading stability and capacity. Explorations were extended to vesicular, multi-compartment, double helix, and layer-by-layer micelles with more complex inner structures. Findings Different payloads have their own preferred locations. Decane locates at the hydrophilic/hydrophobic interface, butylbenzene occupies both the hydrophilic/hydrophobic interface and the hydrophobic core, while naphthalene enters the hydrophobic core. More efficient delivery of multi-payloads is achieved since the competition of payloads occupying preferred locations is minimized. The fusion of micelles encapsulating different payloads suggests that specific payloads will move to their preferred positions without interfering other payloads.

A three-dimensional hollow NiCo2O4 structure was successfully prepared with a precipitation-hydrothermal method. A balance between magnetic and dielectric losses was achieved by using a hollow NiCo2O4 structure loaded with benzotriazole (BTA), and thus the performance of electromagnetic waves was attenuated. The minimum reflection loss value of BTA@NiCo2O4 at 16.01 GHz was −35.39 dB when the absorber thickness was 2 mm, at which the absorption bandwidth for an RL of less than −10 dB is as high as 4.64 GHz. The absorption mechanism was characterized by the synergy among interfacial polarization, multiple reflection, and dipole polarization enhancement between NiCo2O4 and BTA. Interestingly, the epoxy/BTA@NiCo2O4 coating not only exhibited an outstanding microwave absorption (MA) performance but also has excellent anticorrosion and self-healing properties, as shown by the results of electrochemical impedance spectroscopy and confocal laser scanning microscopy. This work would be very helpful to the development of novel coatings with excellent MA performance and anticorrosion and self-healing properties.

Dissipative particle dynamics (DPD) simulations were applied to investigate the effect of SiO2 nanoparticles (SNPs) modified with different tertiary amine chain length and concentration on O/W emulsion properties, the influence mechanism was also revealed from the molecular level. On this basis, the influence of the modified SNPs volume fraction in the emulsion system was studied. The results showed that with the increase number of tertiary amine chain alkyl carbon, the stability of the original emulsion system was first enhanced and then weakened while the responsiveness of the protonated emulsion system was first weakened and then slightly enhanced, the number of tertiary amine chains modified on SNPs has the same influence rule on emulsion performance, which was determined by the hydrophobicity of modified SNPs. In addition, with the increase of the modified SNPs volume fraction in the emulsion system, the stability of the emulsion is gradually enhanced. However, when the volume fraction of SiO2 exceeds 3%, the amplitude of stability enhancement decreases. The increase in the interaction energy between oil droplets in the equilibrium process is caused by emulsion fusion, which in turn is affected by SNPs. The repulsive force between oil and water is greater than that between two oil drops, which is the reason for the oil drop fusion. The presence of SNPs can reduce the repulsive force between oil and water to different degrees, thus slowing down the fusion of emulsion.

Self-healing materials with high self-healing efficiency and excellent mechanical properties are desired for practical applications. Herein, imine-based epoxy composites enhanced by surface modified halloysite nanotubes (SiUr@HNTs) were fabricated. According to DSC curves, epoxy composites with 3 wt% of SiUr@HNTs have an excellent cure state. The addition of 3 wt% of SiUr@HNTs not only gives a certain fluidity to the composites to improve the self-healing performance (the tensile strength can restore to 7.10 MPa and the self-healing efficiency can reach 99.8%), but SiUr@HNTs can also be used as a mechanical enhancer to enhance the mechanical properties (the tensile strength increases from 5.16 MPa to 7.12 MPa). In addition, the epoxy composites can withstand large stretching and a weight of more than 400 g after ex situ self-healing. Besides, the epoxy composites have great thermal stability and solvent resistance. In general, this work proposed a method to improve the mechanical properties of self-healing materials, which is promising in the development of high-strength self-healing composite materials.

Molecular dynamics simulations are used to investigate the effects of temperature, strain rate and molecule length on the deformation of graphene/polyethylene composites. At higher temperature, the host molecules move easily to fit the strain during the deformation. When the strain rate is lower, atoms in the composite model are more relaxed to fit the strain, thus the yield stress of the composite model is smaller than that at a higher strain rate. Due to the longer the length of molecules, the relative movement between molecules is more difficult with the increase of the strain, resulting in a larger yield stress.

Pseudomorphic conversion of metal-organic frameworks (MOFs) enables the fabrication of nanomaterials with well-defined porosities and morphologies for enhanced performances. However, the commonly reported calcination strategy usually requires high temperature to pyrolyze MOF particles and often results in uncontrolled growth of nanomaterials. Herein, we report the controlled alkaline hydrolysis of MOFs to produce layered double hydroxide (LDH) while maintaining the porosity and morphology of MOF particles. The preformed trinuclear M3(μ3-OH) (M = Ni2+ and Co2+) clusters in MOFs were demonstrated to be critical for the pseudomorphic transformation process. An isotopic tracing experiment revealed that the 18O-labeled M3(μ3-18OH) participated in the structural assembly of LDH, which avoided the leaching of metal cations and the subsequent uncontrolled growth of hydroxides. The resulting LDHs maintain the spherical morphology of MOF templates and possess a hierarchical porous structure with high surface area (BET surface area up to 201 m2·g-1), which is suitable for supercapacitor applications. As supercapacitor electrodes, the optimized LDH with the Ni:Co molar ratio of 7:3 shows a high specific capacitance (1652 F·g-1 at 1 A·g-1) and decent cycling performance, retaining almost 100% after 2000 cycles. Furthermore, the hydrolysis method allows the recycling of organic ligands and large-scale synthesis of LDH materials.

Dissipative particle dynamics (DPD) simulations were applied to investigate the solution self-assembly and pH-responsive behavior of hydrophobic DCPD (dicyclopentadiene)-loaded microcapsules from triblock copolymers poly (1,2-ethanediol, homopolymer-b-2-Diethylaminoethylmethacrylate-b-methyl methacrylate) (PEG- b -PDMAEMA- b -PMMA). Results indicate that micelles with longer hydrophilic PEG blocks and shorter hydrophobic PMMA blocks were in favor of encapsulating hydrophobic DCPD. Cross-linking at the core/shell interface generates a chemically bonded network structure in the micelle and leads to a significant decrease of their thermodynamic mobility (i.e., the increase of stability). Both non cross-linked and cross-linked micelles show a good pH-responsive behavior. In particular, cross-linked micelles still have the ability to carry DCPD due to the incomplete dispersion even completely protonation of PDMAEMA, which indicates that the cross-linked micelles could be expected to realize the slow release of encapsulated DCPD agent.

Frequent oil spills pose severe damages to the marine ecosystems and result in hazardous fires when the spilled oil is ignited. Developing high-performance, flame-retardant absorbent materials for large-scale water treatment is therefore urgently needed. Herein, we report an efficient post-synthetic silylation process to achieve a porous covalent-organic framework (COF), denoted as [CF3] − COF. The absorption capacity of oils and organic solvents in [CF3] − COF was explored by experimental measurements with the absorption mechanism illuminated by molecular simulations. The prepared [CF3] − COF powders were further loaded into melamine sponge to yield a highly hydrophobic absorbent denoted as [CF3] − COF@sponge, which was demonstrated to effectively remove oils/organic solvents with outstanding stability and excellent flame retardancy. Moreover, an oil-collecting apparatus was designed to continuously separate oils/organic solvents from water. The rapid recovery of oils/organic solvents from water using this device proves the great promise of [CF3] − COF@sponge in water treatment.

The separation of ethylene (C2 H4 ) from a mixture of ethane (C2 H6 ), ethylene (C2 H4 ), and acetylene (C2 H2 ) at normal temperature and pressure is a significant challenge. The sieving effect of pores is powerless due to the similar molecular size and kinetic diameter of these molecules. We report a new modification method based on a stable ftw topological Zr-MOF platform (MOF-525). Introduction of a cyclopentadiene cobalt functional group led to new ftw-type MOFs materials (UPC-612 and UPC-613), which increase the host-guest interaction and achieve efficient ethylene purification from the mixture of hydrocarbon gases. The high performance of UPC-612 and UPC-613 for C2 H2 /C2 H4 /C2 H6 separation has been verified by gas sorption isotherms, density functional theory (DFT), and experimentally determined breakthrough curves. This work provides a one-step separation of the ternary gas mixture and can further serve as a blueprint for the design and construction of function-oriented porous structures for such applications.

Self-assembly of polymer and surfactant mixtures has attracted great interests because of its potential applications, ranging from tertiary oil recovery to drug delivery. However, the mechanism by which the hydrolysis degree of polymers promotes morphology transition is still experimentally challenging. In this study, self-assembly of the cationic surfactant dodecyltrimethylammonium bromide (DTAB) and anionic polyelectrolyte partially hydrolyzed polyacrylamide (HPAM) mixture was investigated by coarse-grained molecular dynamics (CG MD) simulation. In the polymer-surfactant mixtures, a sphere-to-rod transition of aggregates was obtained with the increasing concentration of DTAB. The increase of HPAM hydrolysis degree can promote the morphological transition from spherical into rod-like aggregates. Our simulation revealed that the flexibility of HPAM chain and the electrostatic attraction between DTAB headgroups ( N(CH3)3+) and HPAM carboxylate ions ( COO−) exerted a crucial role in promoting the morphological transition of aggregates. These simulation results brought to light the molecular-level information of sphere-to-rod transitions in polymer-surfactant aggregates. This work is expected to trigger further studies on morphology transition of polymer-surfactant mixtures.

Density functional theory was used to investigate the adsorption of imidazole (IMD), benzotriazole (BTAH) and 2-mercaptobenzoxazole (MBO) on the grain boundary (GB) of Cu (100) surface. Results show that molecules prefer to adsorb on the grain boundary with the larger distortion degree and more adsorption sites. The main interaction of molecules and grain boundary is chemisorption through C, N, S Cu bonds in both perpendicular and parallel modes. Hydrogen bonds and the lateral dipole-dipole interactions are also found. Based on the adsorption behaviour, the coverage effect and charge redistribution might be two possible inhibition mechanisms of inhibitor molecules.

Membrane-based water desalination has drawn considerable attention for its potential in addressing the increasingly limited water resources, but progress remains limited due to the inherent constraints of conventional membrane materials. In this work, by employing state-of-the-art molecular simulation techniques, we demonstrated that two-dimensional hydrocarbon polymer membranes, materials that possess intrinsic and tunable nanopores, can provide opportunities as molecular sieves for producing drinkable water from saline sources. Moreover, we identified a unique relationship between the permeation and selectivity for membranes with elliptical pores, which breaks the commonly known trade-off between the pore size and desalination performance. Specifically, increase in the area of elliptical pores with a controlled minor diameter can offer an improved water flux without compromising the ability to reject salts. Water distributions and water dynamics at atomic levels with the potential of mean force profiles for water and ions were also analyzed to understand the dependence of permeation and selectivity on the pore geometry. The outcomes of this work are instrumental to the future development of ultrathin-film reverse osmosis membranes and provide guidelines for the design of membranes with more effective and efficient pore structures.

Coaxial titanium vanadium nitride core–sheath nanofibers (VN@TiN) with mesoporous structure are fabricated and explored as efficient Pt-free counter electrodes (CEs) for Dye-sensitized Solar Cells (DSCs). For these nanofibers, the TiN core is covered with a sheath of VN, and their boundary is a continuous series of TiVN solid solutions. Both electrochemical tests and density functional theory computations indicate that the combination of core-sheath nanofibers structure design and the formation of TiVN solid solutions significantly enhance the triiodide reduction activity of parental TiN and VN. Impressively, the devices employing VN@TiN core-sheath nanofibers CEs yield 8.98%, which is 17% higher than that device with Pt CE (7.64%). The design strategy developed in this study may promote a boom in a promising alternative CE for future large-scale application of DSCs.

Molecular dynamics simulations were used to investigate the aggregation of two partially overlapped graphene sheets in hexane, dodecane and eicosane. When partially overlapped graphene shee...

Dissipative particle dynamics (DPD) simulation is used to study the effect of pH on the morphological transition in micelles assembled from dirhamnolipids (diRLs), and analyze the pH-driven mechanism and influence factors of micellar surface patterns. At pH4.0, various multilayer structures with homogeneous surface patterns are observed, whereas diRLs can self-assemble into novel anisotropic morphologies with phase-separated surface patterns at pH7.4, such as patchy spherical micelles, rod-like micelles with helical surface patterns and a lamellar phase with anisotropic surface patterns. The change in a surface pattern results from the diverse molecular arrangement in the course of assembly due to the deprotonation of carboxyl groups. Further studies show that influence factors, such as molecular structure, solvent selectivity and intramolecular interaction, are closely associated with the changes in surface patterns and topological structures. In detail, decreasing the critical packing parameter of rhamnolipids, increasing the solution polarity and weakening the compatibility between rhamnose rings and alkyl chains are all beneficial to the formation of phase-separated surface patterns. Remarkably, a wider variety of surface patterns (randomly anisotropic surface patterns) can be further obtained with the different factors mentioned above. This work is expected to extend the applications of diRLs to advanced functional materials like drug delivery, optoelectronics and nanofiltration membranes.

Smart coatings depending on external nanocontainers are often complex and expensive, which can only inhibit local corrosion depending on the microenvironment change after corrosion. In this work, nanocatalytic anticorrosion based on silica coated nitrogen enriched hollow carbon spheres (NHCs@mSiO2) is developed to achieve the prolongation of coating lifetime and long-term protection of metals. Obtained NHCs@mSiO2 by confined space pyrolysis strategy shows a double-shelled hollow structure with interior N-doped carbon shell and exterior silica shell. Moreover, the NHCs@mSiO2 spheres possess favorable catalytic ability for oxygen thanks to the incorporation of nitrogen. When blended into epoxy coatings, amphiphilic NHCs@mSiO2 spheres distribute uniformly and occupy the pores or cracks in composite coatings. The diffused oxygen through coating micropores are preferentially adsorbed by NHCs@mSiO2 and directly reduced to water through four-electron pathways. Therefore, the corrosion is greatly avoided due to the depletion of oxygen. The introduction of nano-catalyst with excellent dispersity and oxygen reduction ability will pave the way toward the development of new smart coatings with active corrosion resistance.

Molecular dynamics simulations were performed to explore the effect of linker configuration and functionalization on the desalination of Zr-MOF membranes. PTP containing diphenyl rings at linker end and one triple bond at middle has the best permeability (34.50 L/cm2 day MPa). PTP was functionalized by –OH, –CH3, -CF3 and -Cl at two positions that are closer to metal cluster or middle of linker. The Zr-MOF membrane with unmodified PTP has a salt rejection rate 72%, while after functionalization the maximum value reaches 93%. The attraction and blocking effect of functionalized linkers lead to different water permeations and salt rejection rates.

Separation of methane and ethane using porous materials is a challenge. Size exclusion will reduce the working capacity and increase the difficulty of material fabrication. Covalent organic frameworks (COFs) are hopeful due to the adsorption selectivity of C2H6/CH4 and other advantages. In this paper, we used the grand canonical Monte Carlo (GCMC) simulations to study the adsorption behavior of 1171 theoretical two-dimensional (2D) imine COFs, focusing on the effects of monomer structure and composition on the and C2H6/CH4 separation performance. 11 structures with excellent performance were screened according to C2H6 working capacity and the C2H6/CH4 selectivity. COFs with trigonal nodes were found to have better performance than that with tetragonal nodes. It is supposed that the shape, size, and spatial ductility of the nodes have important effects on structural parameters such as largest free sphere diameter (LCD), surface area, and void fraction. In addition, the nitrogen content of these COFs also has a significant effect on the separation performance of CH4 and C2H6, which is mainly related to the way of nitrogen introduction. We hope that the results of this study can provide guidance for the monomer selection and structural design of the separation materials for CH4 and C2H6.

Density functional theory calculation was conducted to investigate the adsorption behavior and mechanism of benzotriazole (BTA) on the copper surface with the defects of vacancy, impurity, and grain boundary (GB). On the Cu (111) surface with vacancies, BTA tends to obliquely, rather than vertically, adsorb on the copper surface. The surface doped with Zn and O has stronger adsorption activity for negatively charged particles compared with the surface doped with Ni and S. For impurity and GB surface, the adsorption energy and transferred charge show that the oblique and horizontal adsorption configurations are more stable than the vertical adsorption of BTA. Our findings provide profound explanation for corrosion inhibitor protection of defective metal surface.

Molecular dynamics (MD) simulations were implemented to investigate the effect of single adatom (SA) and Stone-Wales (SW) defects on the longitudinal elastic properties of unidirectional carbon nanotube (CNT)/polypropylene (PP) composites. The longitudinal Young's moduli of individual CNTs and CNT/PP composites were calculated from uniaxial tension simulations, and the interfacial shear strengths (IFSSs) between CNTs and PP matrix were also extracted. The moduli of SA and SW defected CNT/PP composites decrease with the increase of the defect degree, and SW defects have a greater impact on the moduli than SA defects. Moreover, the intrinsic moduli of the CNTs with SA and SW defects also decrease due to the structural relaxations under tension loading as the defect degree increases. However, the IFSSs of SA and SW defected CNT/PP composites tardily decrease and increase with the increase of the defect degree, respectively. Analysis of the parametric loss ratios indicates that the longitudinal elastic properties of SA and SW defected CNT/PP composites strongly depend on that of the CNTs, and the variation of interfacial bonding characteristics caused by SA and SW defects might have a negligible effect.

Dissipative particle dynamics (DPD) simulations were applied to investigate the coating repair agent dicyclopentadience (DCPD) in pH-sensitive micelles. The results show micelles self-assembled from triblock copolymers with strong hydrophobic interaction are not conducive to loading DCPD, and only micelles with weak interaction parameter can encapsulate DCPD well. After protonation, the structure of micelle was disassembled and DCPD beads have a stronger ability to shrink polymer chains and exposed to water. This work provides mesoscopic insight into self-assembly and disassembly of desired agent-loaded micelle, and might be useful for the design of new materials for agent delivery.

Molecular dynamics simulations have been carried out to study the stability of gemini surfactant foam with different head groups. The results showed that the interaction strength between the polar head groups of the surfactants and water molecules increased from 12-3S-12 (sulfate) system, 12-3Sn-12 (sulfonate) system to 12-3L-12 (carboxylate) system, and the coordination number of water molecules around head increased. From the perspective of energy, the interface formation energy of 12-3L-12 system was smallest, which means that the foam stability was the best. These results indicated that the different head type had a significant effect on the stability of gemini surfactant foam.

Molecular dynamics simulations are used to investigate the effect of graphene dispersion on the equilibrium structure and deformation of graphene/eicosane composites. Two graphene sheets with four different interlayer distances are incorporated, respectively, into a eicosane matrix to form graphene/eicosane composites representing different graphene dispersions. With greater graphene dispersion, the “adsorption solidification” of the eicosane increases, where eicosane molecular lamination, orientation, and extension become more uniform and stronger. In addition, eicosane molecular motion is inhibited more in the direction perpendicular to graphene surfaces. When these graphene/eicosane composites are deformed, the free volume initially increases slowly due to small, scattered voids. After reaching the yield strains, the free volume rises sharply as the structures of composites are damaged, and small voids merge into large voids. The damage always occurs in the region of the composite with the weakest “adsorption solidification.” Since this effect is stronger when the graphene sheets are more dispersed, more complete dispersion results in higher composite yield stresses. Lessons from these simulations may provide some insights into graphene/polyethylene composites, where suitable models would require very long equilibration times.

Ordered and flexible porous frameworks with solution processability are highly desirable to fabricate continuous and large-scale membranes for the efficient gas separation. Herein, the first microporous hydrogen-bonded organic framework (HOF) membrane has been fabricated by an optimized solution-processing technique. The framework exhibits the superior stability because of the abundant hydrogen bonds and strong π-π interactions. Thanks to the flexible HOF structure, the membrane possesses the unprecedented pressure-responsive H2 /N2 separation performance. Furthermore, the scratched membrane can be healed by the treatment of solvent vapor, achieving the recovery of separation performance.

One-atom-thick materials hold promise for the future of membrane-based gas purification and water filtration applications. However, there are a few investigations on the mechanical properties of these materials under pressure-driven condition. Here, by employing molecular simulation techniques and continuum mechanics simulation, we investigate the mechanical strength of two-dimensional hydrocarbon polymers containing sub-nanometer pores with various topologies. We demonstrate that the mechanical strengths of the membranes are correlated with their pore sizes and geometries. In addition, when the pore size of substrates is controlled within a reasonable range, all of the membrane candidates can withstand the practical hydraulic pressure of few megapascal. The studied materials also exhibit better seawater desalination performance as compared to the traditional polymeric reverse osmosis membrane. This work presents a new route to design new separation membrane, and also propose a simulation method to evaluate the mechanical strength and desalination performance.

The pullout process of graphene from an epoxy/graphene composite filled with a carbon nanotube (CNT) was simulated by molecular dynamics simulations. The interaction energy and the interfacial adhesion energy were calculated to analyze the effect of CNT addition on the interfacial adhesion between the graphene and the epoxy matrix, with varying CNT radii, distances between the CNT and the graphene sheet, CNT axial directions, and the number of CNT walls. Generally, the addition of a CNT strengthens the interfacial adhesion between the graphene and the polymer matrix. Firstly, a larger CNT radius induces a stronger interfacial adhesion of graphene with the matrix. Secondly, when the CNT is farther away from the graphene sheet, the interfacial adhesion of graphene with the matrix becomes weaker. Thirdly, the CNT axial direction has little effect on the interfacial adhesion of graphene in the equilibrium structure. However, it plays an important role in the graphene pullout process. Finally, compared with a single-walled CNT, the interfacial adhesion between graphene and the matrix is stronger when a double-walled CNT is added to the matrix.

In the lifting process of drainage gas recovery, external conditions and internal components of the foam are complex. We used molecular dynamics simulation to construct a series of fatty alcohol polyoxyethylene ether sulfate (AES) foam models that could represent various foams in different lifting stages from well to ground. The effect of temperature and pressure on foam stability was investigated. We found that there are two main reasons for foam instability in the first-half stage of the lifting process. Firstly, high temperature aggravated the molecule movement; some CH4 molecules entered the foam film and formed a molecular transport channel. Secondly, the interaction between the CH4 phase and condensate oil leads to some alkane molecules entering the gas–liquid interface. The calculation results and theoretical analysis will help to deepen the understanding of the performance of oily foams under harsh conditions.

Developing high-performance materials for efficient isolation of proteins is of great importance. Herein, the authors synthesized a series of magnetic Fe3O4@PS-ANTA-M2+ (M = Ni, Co, Cu and Zn) nanospheres, consisting of fine Fe3O4 nanoparticles encapsulated by functionalized polystyrene shell, where metal ions were complexed by Nα, Nα-Bis(carboxymethyl)-L-lysine hydrate for selectively immobilizing histidine (His)-tagged proteins. The structures of the Fe3O4@PS-ANTA-M2+ were studied by field scanning electron microscopy, transmission microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and vibrating sample magnetometer. The adsorption performance of the Fe3O4@PS-ANTA-M2+ was studied using bovine hemoglobin as a model protein. The thermodynamics of the binding process was studied by isothermal titration calorimetry tests. The resulting Fe3O4@PS-ANTA-Cu2+, Fe3O4@PS-ANTA-Ni2+, Fe3O4@PS-ANTA-Co2+ and Fe3O4@PS-ANTA-Zn2+ possessed adsorption capacities of 21200, 8080, 6640 and 5360 mg g−1, respectively, rendering them as the best adsorbents for protein purification. The adsorption isotherm was better fitted by Langmuir equation. To verify the selectivity, the Fe3O4@PS-ANTA-M2+ was practically employed to isolate His-tagged proteins from cell lysate. The results indicated that the samples showed outstanding adsorption capacity, selectivity and stability, and facile regeneration and separation, outperforming a commercial NTA-Ni column. These findings suggested that the Fe3O4@PS-ANTA-M2+ showed promising applications for specifically isolating proteins from complex biological systems.

Metal corrosion has spread all over all aspects of national economy and life, causing serious economic losses and ecological hazards. Because of its excellent protective effect and universality, coating has become an important choice for metal corrosion protection. Although the conventional coating can realize metal corrosion protection with its shielding effect, the protection performance gradually decreases due to mechanical damage and corrosive species erosion. Based on the actual corrosion reaction process, the concept of nanocatalytic anticorrosion is proposed in this work to realize the long-term protection for metals. Firstly, oxygen reduction catalyst was obtained by confined pyrolysis and added into epoxy resin to prepare a new nanocatalytic anticorrosion coating, and then the protective performance of the coating was studied in detail. The results show that the catalyst adopt a uniform dodecahedral structure with excellent oxygen reduction ability, the half wave potential is 0.85 V. The catalyst added in the coating can spontaneously consume the diffused oxygen in the coating while enhancing the compactness of the coating to block the corrosive medium, reduceing the contribution of the corrosive medium to the corrosion reaction. Therefore, the probability of metal corrosion can be significantly reduced, and the service life of the coating for metal protection has been greatly prolonged.

The adsorption behavior of CO2, CH4 and their mixtures in bituminous coal was investigated in this study. First, a bituminous coal model was built through molecular dynamic (MD) simulations, and it was confirmed to be reasonable by comparing the simulated results with the experimental data. Grand Canonical Monte Carlo (GCMC) simulations were then carried out to investigate the single and binary component adsorption of CO2 and CH4 with the built bituminous coal model. For the single component adsorption, the isosteric heat of CO2 adsorption is greater than that of CH4 adsorption. CO2 also exhibits stronger electrostatic interactions with the heteroatom groups in the bituminous coal model compared with CH4, which can account for the larger adsorption capacity of CO2 in the bituminous coal model. In the case of binary adsorption of CO2 and CH4 mixtures, CO2 exhibits the preferential adsorption compared with CH4 under the studied conditions. The adsorption selectivity of CO2 exhibited obvious change with increasing pressure. At lower pressure, the adsorption selectivity of CO2 shows a rapid decrease with increasing the temperature, whereas it becomes insensitive to temperature at higher pressure. Additionally, the adsorption selectivity of CO2 decreases gradually with the increase of the bulk CO2 mole fraction and the depth of CO2 injection site.

Molecular dynamics simulations were carried out to investigate the influence of cations (Ca2+/Mg2+) on the stability of the foam system stabilized by sodium dodecyl polyoxyethylene sulfonate (A12E2SO3). First, the structure of A12E2SO3 monolayer at the air/water interface was studied through analyzing the distribution of A12E2SO3 headgroups and the orientation of surfactant molecules. Results show that the addition of Mg2+ can increase the distance between A12E2SO3 headgroups, broaden the distribution thickness of A12E2SO3 headgroups along z axis, and improve the orientation of A12E2SO3 molecules, which favored the foam stability. On the contrary, the addition of Ca2+ in the foam system made surfactant molecules more aggregated, which was detrimental to the foam stability. Second, the interaction of surfactant molecules and cations was also studied through calculating their binding/dissociation energy and mobility. Results reveal that the binding tendency of the head-Ca2+ ion-pair was stronger than that of the head-Mg2+ ion-pair, which disturbed the foam stability. Third, we studied the hydration of surfactant headgroups and cations through calculating the number and the mobility of hydrated water molecules around headgroups. Results show that due to the extra hydration of cations in the foam system, especially for that with the addition of Mg2+, the number of water molecules around headgroups was increased and their mobility was restricted, which was beneficial to the foam stability. In addition, two forms of hydrogen bond bridging structures (O1⋯H2O⋯O2 and O2⋯H2O⋯Os) were observed for the first time in anionic surfactants. The location and the formation probability of these structures were found to be related to the gauche conformation of A12E2SO3 headgroup backbones. It was also found that hydrogen bond bridging structures can affect the foam stability.

Ultrafiltration (UF) membranes have found great application in sewage purification and desalination due to their high permeation flux and high rejection rate for contaminants under low-pressure conditions, but the flux and antifouling ability of UF membranes needs to be improved. Tetrakis (4-carboxyphenyl) porphyrin (TCPP) has good hydrophilicity, and it is protonated under strongly acidic conditions and then forms strong hydrogen bonds with N, O and S, so that the TCPP would be well anchored in the membrane. In this work, NaHCO3 was used to dissolve TCPP and TMC (trimesoyl chloride) was used to produce a strong acid. Then, TCPP was modified in a membrane with a different rejection rate by a method similar to interfacial polymerization. Performance tests of TCPP/polysulfone (PSf) membranes show that for the membrane with a high BSA (bovine serum albumin) rejection, when the ratio of NaHCO3 to TCPP is 16:1 (wt.%), the pure water flux of membrane Z1 16:1 is increased by 34% (from 455 to 614 Lm&minus, 2h&minus, 1bar&minus, 1) while the membrane retention was maintained above 95%. As for the membrane with a low BSA rejection, when the ratio of NaHCO3 to TCPP was 32:1, the rejection of membrane B2 32:1 was found to increase from 81% to 96%. Although the flux of membrane B2 32:1 decreased, it remained at 638 Lm&minus, 1, which is comparable to the reported polymer ultrafiltration membrane. The above dual results are thought to be attributed to the synergistic effect of protonated TCPP and NaHCO3, where the former increases membrane flux and the latter increases the membrane rejection rate. This work provides a way for the application of porphyrin and porphyrin framework materials in membrane separation.

In order to effectively enhance the performances of supercapacitors (SCs), novel electrode materials with high energy density and long cycling lives are urgently needed. Herein, we provide an universal strategy to improve the cycling stablity of transition metal phosphides as supercapacitor electrodes. Ni1.4Co0.6P@C hierarchical core@shell microspheres with abundant electrochemical active sites for large energy storage and coated porous carbon shells for drastically improved conductivity and cycling stability are purposely prepared and obtained. Benefiting from its excellent structural and compositional advantages, the as-derived Ni1.4Co0.6P@C microspheres possess attractive electrochemical properties such as remarkably high specific capacitance (1571.3 F g−1 at 1 A g−1), good rate capability (80.2%, from 1 A g−1 to 25 A g−1), and outstanding cycling stability (retained 82.8% after 5000 cycles). The fabricated all-solid state asymmetric supercapacitor using Ni1.4Co0.6P@C spheres and hollow carbon nanospheres (HCNs) as electrodes delivers the energy density of 40.8 Wh∙kg−1 at a power density of 80.8 W kg−1 and excellent cycling stability (retained 89.3% after 10000 cycles), illustrating its promising application potentials.

The main goal of the current paper is to investigate the surface structure of ionic surfactant solutions at molecular level and the influences of the counter-ion in this course. The used methods are molecular dynamics simulation and neutral impact collision ion scattering spectroscopy. The surfactants are sodium dodecyl sulfate and cesium dodecyl sulfate. With Material Studio (MS), the concentration-depth profiles of all the components in the surface layer have been simulated. With those profiles, the surface pictures of the ionic surfactant solutions are mapped out in angstrom scale and the orientation of surface active dodecyl sulfate ion at the surface dependent on its surface density is derived. Simultaneously, neutral impact collision ion scattering spectroscopy is employed to investigate the same systems experimentally. The results indicate that the surface structure is profoundly influenced by surface density of the surfactant and specificity of the counter-ion; however, the orientation of the dodecyl sulfate ion on the surface is only subjected to its surface density but hardly affected by the properties of its counter-ion. The comparison between those simulated and experimental results reveals reasonable agreements, indicating the reliability of this investigation as well as the reliability of the simulation strategy applied in these systems.

Molecular dynamics simulations at the atomistic level were performed to investigate the glass transition of a highly crosslinked thermoset epoxy resin system composed of diglycidyl ether bisphenol A and isophorone diamine. The crosslinked model was first constructed using a cyclic dynamic method, and extended by investigating the effect of conversion degree on the static properties of local structure, internal energy and volume shrinkage. Based on this model, a systematic investigation on volume, energy and dynamic properties against temperature was made, which determined the glass transition temperature (Tg). The Tgs obtained from various volumetric and energy properties agree well with the differential scanning calorimetry experimental data available, yet a dynamic Tg obtained from the diffusion coefficient is relatively higher. Moreover, the investigation on epoxy segmental dynamics confirmed that the glass transition of the highly crosslinked epoxy resin has a strong dependence on the backbone bond to...

Multicompartment nanostructures, such as microcapsules with clearly separated shell and core, are not easily accessible by conventional block copolymer self-assembly. We assess a versatile computational strategy through cooperative assembly of diblock copolymer blends to generate spherical and cylindrical compartmentalized micelles with intricate structures and morphologies. The co-assembly strategy combines the advantages of polymer blending and incompatibility-induced phase separation. Following this strategy, various nanoassemblies of pure AB, binary AB/AC and ternary AB/AC/AD systems such as compartmentalized micelles with sponge-like, Janus, capsule-like and onion-like morphologies can be obtained. The formation and structural adjustment of microcapsule micelles, in which the shell or core can be occupied by either pure or mixed diblock copolymers, were explored. The mechanism involving the separation of shell and core copolymers is attributed to the stretching force differences of copolymers which drive the arrangement of different copolymers in a pathway to minimize the total interfacial energy. Moreover, by adjusting block interactions, an efficient approach is exhibited for regulating the shell or core composition and morphology in microcapsule micelles, such as the transition from the "pure shell/mixed core" morphology to the "mixed shell/pure core" morphology in the AB/AC/AD micelle. This mesoscale simulation study identifies the key factors governing co-assembly of diblock copolymer blends and provides bottom-up insights towards the design and optimization of new multicompartment micelles.

© 2017 American Chemical Society. Using dissipative particle dynamics simulation, we probe the tunable permeability of cross-linked microcapsules made from pH-sensitive diblock copolymers poly(ethylene oxide)-b-poly(N,N-diethylamino-2-ethyl methacrylate) (PEO-b-PDEAEMA). We first examine the self-assembly of non-cross-linked microcapsules and their pH-responsive collapse and then explore the effects of cross-linking and block interaction on the swelling or deswelling of cross-linked microcapsules. Our results reveal a preferential loading of hydrophobic dicyclopentadiene (DCPD) molecules in PEO-b-PDEAEMA copolymers. Upon reduction of pH, non-cross-linked microcapsules fully decompose into small wormlike clusters as a result of large self-repulsions of protonated copolymers. With increasing degree of cross-linking, the morphology of the microcapsule becomes more stable to pH change. The highly cross-linked microcapsule shell undergoes significant local polymer rearrangement in acidic solution, which eliminates the amphiphilicility and therefore enlarges the permeability of the shell. The responsive cross-linked shell experiences a disperse-to-buckle configurational transition upon reduction of pH, which is effective for the steady or pulsatile regulation of shell permeability. The swelling rate of the cross-linked shell is dependent on both electrostatic and nonelectrostatic interactions between the pH-sensitive groups as well as the other groups. Our study highlights the combination of cross-linking structure and block interactions in stabilizing microcapsules and tuning their selective permeability.

Molecular dynamics simulations are used to investigate the aggregation and behavior of two parallel graphene sheets (22.0–64.0 A in length) in dodecane. The dodecane layer formed on the graphene surface leads to an energy barrier which slows the rate of the graphene aggregation process when the two sheets are totally separated by dodecane molecules. The graphene sheets aggregate in dodecane only when portions of one graphene sheet are in contact with another sheet. The aggregation rate depends on the combined structures of the two graphene sheets. The aggregation rate for two parallel graphene sheets in half contact with one another is constant since the relative sheet geometry and spacing are nearly constant in the transition region between sheets where dodecane molecules are being displaced during aggregation. The aggregation rate for partially overlapped graphene sheets becomes progressively slower as aggregation continues since the area not overlapped decreases as the aggregation proceeds.

Dissipative particle dynamics (DPD) simulation has been used to study the effect of pH on the morphology transition of micelles assembled by monorhamnolipids (monoRLs). Results show that micellar structures and transition modes with increasing mass concentrations are multiform due to the changeable hydrophilicity of pH-responsive beads at different pH levels. Various chaotic multilayer aggregations of monoRLs are observed at low pH (pH4.0) whereas well-ordered single-layer structures are obtained at high pH (pH7.4). At medium pH region (4.0pH7.4), morphologies with semi-chaotic structures will transform from multilayer to single layer with increasing pH due to the hydrophilicity increase of micelles. In addition, three micellar transition modes are built by varying the hydrophilicity of pH-responsive beads and validated by solvent accessible surface areas (SASAs) as a function of mass concentrations. This work is expected to trigger further studies on the stimuli-driven phenomena of glycolipids.

Density functional theory was used to investigate the adsorption of H2S and H/HS, H/H/S on Cu(100). The pathways and transition states of H2S dissociation were also studied. Results show that H2S prefers the top site, while H, S and HS prefer the hollow site during the adsorption process. H2S, HS and S can chemisorb on Cu(100) through the S Cu bond due to the hybridization of the s, p orbit of S and the d orbit of Cu. The order of the adsorption energy for three forms is as follows: H/H/S, H/HS and H2S. In addition, the dissociation of H2S molecule on Cu(100) is thought to be an exothermic process. The activation energy of the first and second S H bonds in H2S are low and similar (approximately 10.15 kcal/mol). In the dissociation of H2S, Cu atoms attract electrons from H S bond which leads the bond-breaking.

A novel CO2/N2 switchable aqueous foam was developed using a CO2-responsive surfactant N,N-dimethyl-N-dodecyl amine (C12A) and a conventional surfactant sodium dodecyl sulfate (SDS). The performance and mechanism of this switchable foam were studied by both experiment and molecular simulation methods. Experimental results demonstrate that the foam stabilized by SDS/C12A surfactants has better stability and water carrying capacity than single C12A foam. The foam could be rapidly switched between stable and unstable states at ambient temperature with CO2 or N2 as the triggers. Simulation results shows that when CO2 was introduced, most of SDS and C12A molecules aggregated in the water phase, instead of adsorbing at the air-water interface to stabilize the foam films. The strong electrostatic attraction between protonated C12A and SDS molecules could account for the aggregation. Due to the presence of limited surfactants located at the air-water interface after introducing CO2, the foam bursts quickly.

Oil phase has strong hydrophobicity and weak interface tension in the foam system, which will destroy the internal structure of foam and reduce the intrinsic stability of the foam film. Coarse-grained molecular simulation techniques were employed to investigate the effect of oil phases on the structural instabilities of two typical foam systems, i.e., ionic sodium dodecyl sulfate (SDS) and nonionic pentaethylene glycol monododecyl ether (C 12 E 5 ). In both systems, the pseudo-emulsion film ruptures at a critical thickness, subsequently the oil phase enters the air-water interface subsequently. Instability mechanisms are obtained by analyzing dynamic processes of the foam systems. For the SDS foam system, an oil-bridge is formed in the foam film, which is attributed to the electrostatic repulsion between the SDS at the oil-water interface and that at the air-water interface, as well as the discontinuous distribution of SDS at the air-water interface caused by the structural reversal of SDS molecules. However, for the C 12 E 5 foam system, oil phase spreads at the air-water interfaces, which is caused by the continuous distribution of the C 12 E 5 molecules at the air-water interface and the attractive interaction between the neutral C 12 E 5 molecules at the air-water interface and that at the oil-water interface. The outcomes of this work shed light on the destructive mechanism of foam films induced by oil phase and provide guidelines for the design of novel oil-resistant foam system.

In this article, decane, methyl benzene, pyridine and acetic acid were selected as different polarity components in crude oil, and their adsorption behavior on water-wet silica surface was investigated by molecular dynamics simulation. Simulation results indicated that polar components could penetrate through water film and adsorb on silica surface, while it was difficult for apolar components. And then, the adsorption mechanism of these four oil components was studied, and researched results showed that the adsorption capability of oil components is related to three factors, viz. interaction between oil components and silica surface, penetration in water film and competitive adsorption with water molecules. Furthermore, how the pre-adsorbed polar components affecting the adsorption of apolar components was investigated. The simulation results demonstrated that the pre-adsorbed polar components could improve the adsorption capability of apolar components. Based on our researches, a two-step adsorption process was proposed, viz. the polar oil components preferentially absorbed on mineral surface, and then these polar components, playing the role of anchor, promoted the adsorption of apolar components. Our researches were beneficial to reveal the adsorption process of oil components in the formation of oil reservoir, which was helpful in guiding the oil-displacing agent design and oil exploitation.

Molecular dynamics simulation method was adopted to investigate the synergistic inhibition mechanism of three inhibitor membranes, including ODD–Cl − , ODD–Br − and ODD–I − . The effects of diffusion coefficient, fractional free volume, self-diffusion coefficient and interaction energy on the synergistic inhibition mechanism were studied. The results demonstrated that the value of diffusion coefficient, fractional free volume, self-diffusion coefficient and interaction energy decreased in the order ODD–Cl − > ODD–Br − > ODD–I − . The synergistic inhibition effect increased in the order ODD–Cl − − − . It agreed well with the previous experimental results.

In this article, the feasibilities of five different monomer aromatic substances as calibration standards by analytical pyrolysis with gas chromatographic separation and mass selective detection (Py-GC/MS) were applied for the quantification of lignin in paper and pulp. The stabilities of these substances in the pyrolysis process were evaluated and the curves of peak response area to mass also were obtained. The results showed that the substances with exact same substitutions on the benzene ring as lignin units had good stabilities in the pyrolysis process with good lineabilities of peak response area to the mass curves, which implicated these substances can be applied as calibration standards in the liginin quick quantitative analyse without tedious pretreatments and structure changes.