Search

Under spherical confinement with different conditions, defects of LCs change from bipolar to striped textures, then change into tetrahedral defects.

Colloidal cubic diamond crystals with low-coordinated and staggered structures could display a wide photonic bandgap at low refractive index contrasts, which makes them extremely valuable for photonic applications. However, self-assembly of cubic diamond crystals using simple colloidal building blocks is still considerably challenging, due to their low packing fraction and mechanical instability. Here we propose a new strategy for constructing colloidal cubic diamond crystals through cooperative self-assembly of surface-anisotropic triblock Janus colloids and isotropic colloidal spheres into superlattices. In self-assembly, cooperativity is achieved by tuning the interaction and particle size ratio of colloidal building blocks. The pyrochlore lattice formed by self-assembly of triblock Janus colloids acts as a soft template to direct the packing of colloidal spheres into cubic diamond lattices. Numerical simulations show that this cooperative self-assembly strategy works well in a large range of particle size ratio of these two species. Moreover, photonic band structure calculations reveal that the resulting cubic diamond lattices exhibit wide and complete photonic bandgaps and the width and frequency of the bandgaps can also be easily adjusted by tuning the particle size ratio. Our work will open up a promising avenue toward photonic bandgap materials by cooperative self-assembly employing surface-anisotropic Janus or patchy colloids as a soft template.

Designing complex cluster crystals with a specific function using simple colloidal building blocks remains a challenge in materials science. Herein, we propose a conceptually new design strategy for constructing complex cluster crystals via hierarchical self-assembly of simple soft Janus colloids. A novel and previously unreported colloidal cluster-χ (χc) phase, which resembles the essential structural features of α-manganese but at a larger length scale, is obtained through molecular dynamics simulations. The formation of the χc phase undergoes a remarkable two-step self-assembly process, that is, the self-assembly of clusters with specific size dispersity from Janus colloids, followed by the highly ordered organization of these clusters. More importantly, the dynamic exchange of particles between these clusters plays a critical role in stabilizing the χc phase. Such a conceptual design framework based on intercluster exchange has the potential to effectively construct novel complex cluster crystals by hierarchical self-assembly of colloidal building blocks.

It remains extremely challenging to build three-dimensional photonic crystals with complete photonic bandgaps by simple and experimentally realizable colloidal building blocks. Here, we demonstrate that particle softness can enhance both the self-assembly of pyrochlore- and perovskite-like lattice structures from simple deformable triblock Janus colloids and their photonic bandgap performances. Dynamics simulation results show that the region of stability of pyrochlore lattices can be greatly expanded by appropriately increasing softness, and the perovskite lattices are unexpectedly obtained at enough high softness. Photonic calculations show that the direct pyrochlore lattices formed from overlapping soft triblock Janus particles exhibit even larger photonic bandgaps than the ideal nonoverlapping pyrochlore lattice, and proper overlap arising from softness can also dramatically improve the photonic properties of the inverse pyrochlore and perovskite lattices. Our study offers a new and feasible self-assembly path toward three-dimensional photonic crystals with large and robust photonic bandgaps.

Controlling the structural order of nanoparticles (NPs), morphology, and composition is of paramount significance in tailoring the physical properties of nanoassembly. However, the commonly reported symmetrical nanocomposites often suffer an interference or sacrifice of the photophysical properties of the original components. To address this challenge, we developed a novel type of organic-inorganic Janus nanocomposite (JNCP) with an asymmetric architecture, offering unique features such as the precisely controlled localization of components, combined modular optical properties, and independent stimuli. As a proof of concept, JNCPs were prepared by incorporating two photoacoustic (PA) imaging agents, namely an organic semiconducting dye and responsive gold nanoparticles (AuNP) assembly in separate compartments of JNCP. Theoretical simulation results confirmed that the formation mechanism of JNCPs arises from the entropy equilibrium in the system. The AuNP assembly generated a PA images with the variation of pH, while the semiconducting molecule served as an internal PA standard agent, leading to ratiometric PA imaging of pH. JNCP based probe holds great potential for real-time and accurate detection of diverse biological targets in living systems.

Amphiphilic building blocks play an important role in fabricating nanomaterials. To achieve the precise control of self-assembled nanostructures, it is important to understand the self-assembly process at both microscopic and mesoscopic scale. Multiscale simulations could simulate the self-assembly process in both microscopic and mesoscopic scale, and get the metastable and equilibrium assembled structures and the corresponding trajectories. Based on these trajectories, we can further build the kinetic network model and obtain the kinetic transition pathway of the self-assembly process. This approach provides the theoretical principles for designing novel self-assembly building blocks and achieving novel self-assembled structures. In this article, we review our recent progress on the study of mechanisms of self-assembly of amphiphilic building blocks, such as small organic molecules, block copolymers and patchy particles by combining multiscale simulation and kinetic network model analysis.

Multiple highly-ordered 2D crystal structures, including a triangular lattice, kagome lattice, and even a Frank–Kasper σ phase, are found within the layers of bilayered lamellae self-assembled directly from 3D systems of soft Janus particles.

Using simple achiral building blocks modulated by an external field to achieve chiral liquid crystal phases remains a challenge. In this study, a chiral helix liquid crystal phase is obtained for a simple Gay-Berne ellipsoid model under an alternating external field by using molecular dynamics simulations. Our results show that the chiral helix liquid crystal phase can be observed in a wide range of external field strengths when the oscillation period is smaller than the rotational characteristic diffusion timescale of ellipsoids. In addition, we find that the pitch and tilt angle of the helix structure can also be adjusted by changing the strength and oscillation period of the applied alternating external field. This may provide a feasible route for the regulation of chiral liquid crystal phases by an alternating external field.

Normally, defects in two-dimensional, circular, confined liquid crystals can be classified into four types based on the position of singularities formed by liquid crystal molecules, i.e., the singularities located inside the circle, at the boundary, outside the circle, and outside the circle at infinity. However, it is considered difficult for small aspect ratio liquid crystals to generate all these four types of defects. In this study, we use molecular dynamics simulation to investigate the defect formed in Gay–Berne, ellipsoidal liquid crystals, with small aspect ratios confined in a circular cavity. As expected, we only find two types of defects (inside the circle and at the boundary) in circular, confined, Gay–Berne ellipsoids under static conditions at various densities, aspect ratios, and interactions between the wall and liquid crystals. However, when introducing an external field to the system, four types of defects can be observed. With increasing the strength of the external field, the singularities in the circular, confined system change from the inside to the boundary and the outside, and the farthest position that the singularities can reach depends on the strength of the external field. We further introduce an alternating, triangular wave, external field to the system to check if we can observe the transformation of different defects within an oscillating period. We find that the position of the singularities greatly depends on the oscillating intensity and oscillating period. By changing the oscillating intensity and oscillating period of the external field, the defect types can be adjusted, and the transformation between different defects can be easily observed. This provides a feasible way to modulate liquid crystal defects and investigate the transformation between different defects.

Probing the transformation from crystalline form II with 11/3 helical structure to form I with 3/1 helical structure in PB-1 and its nanocomposites is of great importance in both scientific fields and commercial applications. The influence of lamellar thickness on the transformation from form II to form I in isotactic polybutylene-1 (PB-1)/carbon nanotube (CNT) nanocomposites was investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS) techniques. The crystallization kinetics of PB-1/CNT nanocomposites at different isothermal temperatures (Tc) indicates that CNTs significantly accelerate the nucleation and growth of form II, acting as heterogeneous nucleating agents. However, the influence of CNTs on the form II–I transformation strongly depends on the lamellar thickness obtained at different Tc, verified by the change in melting point (Tm) and the SAXS results for form I. The addition of CNTs accelerates the transformation and elevates the Tm of form I when the Tc is lower than ∼88 °C, and slows the transformation and slightly decreases the Tm when the Tc is higher than ∼88 °C. This is probably due to the fact that the incorporation of CNTs facilitates an increase in lamellar thickness of form II formed at lower Tc but decreases the lamellar thickness of form II formed at higher Tc. Our study illustrates that the lamellar thickness is one of the key points to determine the transformation from form II to form I in PB-1.

In this study, we investigate the motion of polymer segments in polymer/nanoparticle composites by varying nanoparticle (NP) volume fractions. By studying the probability distribution of segment displacement, segment trajectory, and the square displacement of segment, we find the intermittent motion of segments, accompanied with the coexistence of slow and fast segments in polymer nanocomposites (PNCs). The displacement distribution of segments exhibits an exponential tail, rather than a Gaussian form. The intermittent dynamics of chain segments is comprised of a long-range jump motion and a short-range localized motion, which is mediated by the weakly attractive interaction between NP and chain segment and the strong confinement induced by NPs. Meanwhile, the intermittent motion of chain segments can be described by the adsorption-desorption transition at low particle loading and confinement effect at high particle loading. These findings may provide important information for understanding the anomalous motion of polymer chains in the presence of NPs.

The capability of polyelectrolyte brushes to spontaneously clean oil fouling via water is determined by factors including water wettability and the self-assembled structures of hydrated polyelectrolytes. Although the charged groups of polyelectrolytes provide the original source of water wettability, the self-assembled structures play a significant role in the self-cleaning performances. Here, we employ coarse-grained molecular dynamics simulations to study the general self-cleaning characteristics of two types of surface-grafted polyelectrolyte brushes (i.e., zwitterionic and anionic polyelectrolytes). It has been found that the high grafting density is favorable to fouling reduction for both polyzwitterions and polyanions. To be specific, the hydrated polyzwitterions form an intermolecular cross-linked network via zwitterionic complexes, resulting in better self-cleaning capabilities than the polyanions at lower grafting densities. However, polyanions form bundles with each consisting of several chains via hydrophobic interactions and electrostatic repulsions presenting better self-cleaning performances than the polyzwitterions at higher grafting densities.

Designing complex cluster crystals with a specific function using simple colloidal building blocks remains a challenge in materials science. Herein, we propose a conceptually new design strategy for constructing complex cluster crystals via hierarchical self-assembly of simple soft Janus colloids. A novel and previously unreported colloidal cluster-χ (χ

Topological defects in liquid crystals under confined geometries have attracted extensive research interests. Here, we perform molecular dynamics simulations to investigate the formation and transition of defect patterns in two-dimensional smectic Gay-Berne liquid crystals with a simple rectangular confinement boundary. Two typical types of defect patterns, bridge and diagonal defect patterns, are observed, which can be transformable continuously between each other over time. The transition usually starts from the line or point defect regions, and the competition between neighboring and opposite boundary effects induces the continuous realignments of the smectic layers to connect the neighboring or opposite walls. The relative stability of these two defect patterns can be controlled by changing the confinement conditions. These results deepen our understanding of transition kinetics of defect patterns in confined liquid crystals.

Reversible chemistries have been extensively explored to construct highly crystalline covalent organic frameworks (COFs) via defect correction. However, the mechanisms of defect correction that can explain the formation of products as single crystals, polycrystal/crystallites, or amorphous solids remain unknown. Herein, we employed molecular dynamics simulations combined with a polymerization model to investigate the growth kinetics of two-dimensional COFs. By virtue of the Arrhenius two-state model describing reversible reactions, we figured out the conditions in terms of active energy and binding energy for different products. Specifically, the ultraslow growth of COFs under high reversibility of reactions corresponding to low binding energies resulted in a single crystal by inhibiting the emergence of nuclei as well as correcting defects through continually dropping small defective fragments off at crystal boundaries. High bonding energies responsible for the high nucleation rate and rapid growth that incorporated defects in crystals and caused the division of crystals through defect correcting processes led to small crystallites or polycrystals. The insights into the mechanisms help us to understand and further control the growth kinetics by exploiting reversible conditions to synthesize COFs of higher quality.

Synthesis of covalent organic frameworks with long-range molecular ordering is an outstanding challenge due to the fact that defects against predesigned topological symmetries are prone to form and break crystallization. The physical origins and controlling parameters of topological defects remain scarcely understood. By virtue of molecular dynamics simulations, we found that pentagons for combination [C4 + C4] and [C4 + C2] and heptagons for [C3 + C3] and [C3 + C2] were initial defects for growth dynamics with both uncontrolled and suppressed nucleation, further inducing more complex defects. The defects can be significantly reduced by achieving the growth with monomers added to a single nucleus, agreeing well with previous simulations and experiments. To understand the nature of defects, we proposed a parameter φ to describe the range of biased rotational angle between two monomers, within which chemical reactions are allowed. The parameter φ shows a monotonic relationship with defect population, which is demonstrated to be highly computable by using density functional theory calculations. When φ < 20, we can even observe defect-free growth for the four combinations, irrespective of growth dynamics. The results are essential for screening and designing condensation reactions for the synthesis of single crystals of high quality.

Synthetic vesicles of amphiphilic Janus dendrimers are known as dendrimersomes. The understanding of the conditions and formation mechanism of dendrimersomes is meaningful for further controlling the structures. Herein, the characteristics of the self-assembly of amphiphilic Janus dendrimer/water solutions into unilamellar and onion-like dendrimersomes are studied by molecular dynamics simulations via a spherical single-site Janus particle model. The model with two distinct surfaces, one hydrophobic side and another hydrophilic side, describes the amphiphilic nature of Janus dendrimers. By reducing the dendrimers with complex architectures to be simple Janus particles, we investigate the concentration-dependent self-assembled structures as well as the enthalpy-driven formation process of onion-like dendrimersomes, in contrast to the entropy-mediated self-assembly of amphiphilic flexible chains. Three typical equilibrium morphologies including linear micelles, lamellar structures and vesicles are found upon varying the Janus balance and dendrimer concentration. It is observed that the dendrimersomes consisting of the dendrimers with neglectable molecular configuration entropy become very stable, which agrees well with experimental observation. Specifically, different from many lipidsomes and polymersomes which can spontaneously merge, the size of dendrimersomes will not increase through mutual fusion once the well-defined onion-like structure is formed. Moreover, the discharge of water is achieved by water diffusion in our simulations, instead of in the "peeling-one-onion-layer-at-a-time" fashion. Our study combined with the previous ones using flexible chain models could depict a complete picture of dendrimersomes in favor of their applications in drug and gene delivery.

Tert-butyl-substituted tetramethylcyclopentadiene [C5HMe 4 Bu] was reacted with Ru3(CO)12 to prepare [(η5-C5Me 4 Bu)Ru(CO)(μ-CO)]2. The complex was characterized by IR, 1H NMR, 13C NMR, elemental analysis, and single-crystal X-ray diffraction. The complex was investigated as a catalyst in the aerobic oxidation of alcohols to the corresponding aldehydes and ketones in the presence of 2,2’,6,6’-tetramethylpiperidine N-oxide (TEMPO) as co-oxidant. The combination of [(η5-C5Me 4 Bu)Ru(CO)(μ-CO)]2 and TEMPO afforded an efficient catalytic system for the aerobic oxidation of a variety of primary and secondary alcohols, giving the corresponding carbonyl compounds in good-to-excellent yields.

Reactions of the substituted tetramethylcyclopentadienes [C5HMe4R] [R = t Bu, Ph, CH2CH2C(CH3)3] with Mo(CO)3(CH3CN)3 in refluxing xylene gave a series of dinuclear molybdenum carbonyl complexes [(η5-C5Me4R)Mo(CO)3]2 [R = t Bu (1), Ph (2), CH2CH2C(CH3)3 (3)], [(η5-C5Me t Bu)Mo(μ-CO)2]2 (4)], and [(η5-C5Me4) t Bu]2Mo2O4(μ-O) (5)], respectively. Complexes 1–5 were characterized by elemental analysis, IR, 1H NMR, and 13C NMR spectroscopy. In addition, their crystal structures were determined by X-ray crystal diffraction analysis. The catalytic activities of complexes 1–3 in Friedel–Crafts acylation in the presence of o-chloranil has also been investigated; the reactions were achieved under mild conditions to give the corresponding products in moderate yields.

We describe the algorithm of employing multi-GPU power on the basis of Message Passing Interface (MPI) domain decomposition in a molecular dynamics code, GALAMOST, which is designed for the coarse-...

Hollow polyhedral cages hold great potential for application in nanotechnological and biomedical fields. Understanding the formation mechanism of these self-assembled structures could provide guidance for the rational design of the desired polyhedral cages. Here, by constructing kinetic network models from extensive coarse-grained molecular dynamics simulations, we elucidated the formation mechanism of the dodecahedral cage, which is formed by the self-assembly of patchy particles. We found that the dodecahedral cage is formed through increasing the aggregate size followed by structure rearrangement. Based on this mechanistic understanding, we improved the productivity of the dodecahedral cage through the rational design of the patch arrangement of patchy particles, which promotes the structural rearrangement process. Our results demonstrate that it should be a feasible strategy to achieve the rational design of the desired nanostructures via the kinetic analysis. We anticipate that this methodology could be extended to other self-assembly systems for the fabrication of functional nanomaterials.

We developed dual biologically responsive nanogapped gold nanoparticle vesicles loaded with immune inhibitor and carrying an anticancer polymeric prodrug for synergistic concurrent chemo-immunotherapy against primary and metastatic tumors, along with guided cargo release by photoacoustic (PA) imaging in the second near-infrared (NIR-II) window. The responsive vesicle was prepared by self-assembly of nanogapped gold nanoparticles (AuNNPs) grafted with poly(ethylene glycol) (PEG) and dual pH/GSH-responsive polyprodug poly(SN38-co-4-vinylpyridine) (termed AuNNP@PEG/PSN38VP), showing intense PA signal in the NIR-II window. The effect of the rigidity of hydrophobic polymer PSN38VP on the assembled structures and the formation mechanism of AuNNP@SN38 Ve were elucidated by computational simulations. The immune inhibitor BLZ-945 was encapsulated into the vesicles, resulting in pH-responsive release of BLZ-945 for targeted immunotherapy, followed by the dissociation of the vesicles into single AuNNP@PEG/PSN38VP. The hydrophilic AuNNP@PEG/PSN38VP nanoparticles could penetrate deep into the tumor tissues and release the anticancer drug SN38 under the reductive environment. A PA signal in the NIR-II window in the deep tumor region was obtained. The BLZ-945-loaded vesicle enabled enhanced PA imaging-guided concurrent chemo-immunotherapy efficacy, inhibiting the growth of both primary tumors and metastatic tumors.

The design and discovery of new two-dimensional materials with desired structures and properties are always one of the most fundamental goals in materials science. Here we present an atom-mimicking design concept to achieve direct self-assembly of two-dimensional low-coordinated open lattices using three-dimensional patchy particle systems. Besides honeycomb lattices, a new type of two-dimensional square-octagon lattice is obtained through rational design of the patch configuration of soft three-patch particles. However, unexpectedly the building blocks with thermodynamically favoured patch configuration cannot form square-octagon lattices in our simulations. We further reveal the kinetic mechanisms controlling the formation of the honeycomb and square-octagon lattices. The results indicate that the kinetically favoured intermediates play a critical role in determining the structure of obtained open lattices. This kinetics-controlled design principle provides a particularly effective and extendable framework to construct other novel open lattice structures.

In the present study, we report the development of magnetic-plasmonic bilayer vesicles assembled from iron oxide-gold Janus nanoparticles (Fe3O4-Au JNPs) for reactive oxygen species (ROS) enhanced chemotherapy. The amphiphilic Fe3O4-Au JNPs were grafted with poly(ethylene glycol) (PEG) on the Au surface and ROS-generating poly(lipid hydroperoxide) (PLHP) on the Fe3O4 surface, respectively, which were then assembled into vesicles containing two closely attached Fe3O4-Au NPs layers in opposite directions. The self-assembly mechanism of the bilayered vesicles was elucidated by performing a series of numerical simulations. The enhanced optical properties of the bilayered vesicles were verified by the calculated results and experimental data. The vesicles exhibited enhanced T2 relaxivity and photoacoustic properties over single JNPs due to the interparticle magnetic dipole interaction and plasmonic coupling. In particular, the vesicles are pH responsive and disassemble into single JNPs in the acidic tumor environment, activating an intracellular biochemical reaction between the grafted PLHP and released ferrous ions (Fe2+) from Fe3O4 NPs, resulting in highly efficient local ROS generation and increased intracellular oxidative stress. In combination with the release of doxorubicin (DOX), the vesicles combine ROS-mediated cytotoxicity and DOX-induced chemotherapy, leading to greatly improved therapeutic efficacy than monotherapies. High tumor accumulation efficiency and fast vesicle clearance from the body were also confirmed by positron emission tomography (PET) imaging of radioisotope 64Cu-labeled vesicles.

A series of six alkyl-substituted tetramethylcyclopentadienyl mononuclear metal carbonyl complexes [(η 5-C5Me4R)Re(CO)3] [R = allyl (1), i-Pr (2), n-butyl (3), t-butyl (4), benzyl (5), CH(CH2)4 (6)] have been synthesized by treating the corresponding ligands (C5Me4R) [R = allyl, i-Pr, n-butyl, t-butyl, benzyl, CH(CH2)4] with Re2(CO)10 in refluxing xylene. The six new complexes were characterized by elemental analysis, IR, 1H NMR and 13C NMR spectroscopy. The crystal structures of all six complexes were determined by X-ray crystal diffraction analysis, showing that they have similar molecular structures, being mononuclear carbonyl complexes. In each of these complexes, the Re atom is η 5 -coordinated to the cyclopentadienyl ring. Complexes 1–5 have significant catalytic activity in Friedel–Crafts reactions of aromatic compounds with alkylation reagents. Compared with traditional catalysts, these mononuclear rhenium carbonyl complexes have obvious advantages such as lower amounts of catalyst, mild reaction conditions and environmentally friendly chemistry.

In lithium-ion batteries, separator serves to isolate the positive and negative electrodes, as well as provide a free shuttle for Li-ion transport inside the battery. Commercial polyolefin separator has relatively higher thermal shrinkage and lower electrolyte wettability, which limits the application of batteries in extreme conditions. In this work, we prepared phenolic resin (AF) modified polyethylene (PE) composite separators by the process of immersion in situ reaction. The obtained PE@AF composite separator has lower thermal shrinkage and higher electrolyte wettability than pure PE separator. The shrinkage of our prepared PE@AF separator is only 6% when stored at 145 °C for 30 min, greatly smaller than the pure PE separator (more than 77%). Moreover, the ion conductivity of PE@AF composite separator increases from 0.206 mS cm−1 for the pure one to 0.604 mS cm−1. Apart from this, the Li/electrolyte-soaked PE@AF separator/LiFePO4 battery exhibits a higher coulombic efficiency (96.7%) and discharge capacity retention rate (86.0%) after 450 cycles than the pure one (67.4% and 72.7%, respectively). Our results indicate that the AF coating plays a vital part in improving the thermal stability and electrochemical property of polyolefin separators.

The wheelchair climbing-stairs is a complex mehatronics system, which includes the front leg mechanism, rear leg mechanism, seat mechanism, and so on. Each has an independent CPU to control itself motion. Their coordination can implement the climbing-stair act for the wheelchair climbing robot. Firstly, the paper presents the control system platform for the wheelchair robot, and introduces its functions and requirements. Secondly, describes the process of each component work, such as, the front leg mechanism, rear leg mechanism, and seat mechanism. And designs a control system platform to implement their act based on VC++6.0 software. Finally, the serial communication protocol is given to describe the data exchange process of the upper and lower CPUs towards wheelchair climbing-stairs.

We present a general patchy ellipsoidal particle model suitable for conducting dynamics simulations of the aggregation behaviors of various shape- and/or surface-anisotropic colloids, especially patchy ellipsoids with continuously variable shape and tunable patchiness. To achieve higher computational efficiency in dynamics simulations, we employ a multi-GPU acceleration technique based on a domain decomposition algorithm. The validation and performance evaluation of this GPU-assisted model are performed by simulating several typical benchmark systems of non-patchy and patchy ellipsoids. Given the generality and efficiency of our GPU-assisted patchy ellipsoidal particle model, it will provide a highly feasible dynamics simulation framework to investigate the aggregation behaviors of anisotropic soft matter systems comprised of shape- and/or surface-anisotropic building blocks.

Because of the unique architectures and promising potential applications of biomimetic helical structures in biotechnology and nanotechnology, the design and fabrication of these structures by experimentally realizable anisotropic colloidal particles remain one of the most challenging tasks in materials science. Here we show how soft Janus particles self-assemble into supracolloidal helices with distinctive structural characteristics, including single helices, double helices, and Bernal spirals, by appropriately tuning the particle softness. We further examine the kinetic mechanisms governing the formation of different helical structures by using particle-based dynamics simulations. Our results provide a new way for experimentally fabricating structure-controllable supracolloidal helices solely from the self-assembly of soft Janus particles.

Molecular dynamics simulations are useful tools to unveil molecular mechanisms of polymer phase separation, self-assembly, adsorption, and so on. Due to large molecular size and slow relaxation of the polymer chains, a great amount of issues related to large-distance chain displacement cannot be tackled easily with conventional molecular dynamic simulations. Systematic coarse-graining and enhanced sampling methods are two types of improvements that can boost spatiotemporal scales in polymer simulations. We present two typical ways to obtain the coarse-graining potential either by fitting to correct liquid structures or by fitting to available thermodynamic properties of polymer systems. The newly proposed anisotropic coarse-grained particle model can be used to describe aggregation and assembly of polymeric building blocks from disk-like micelles to Janus particles. We also present a stochastic polymerization model combined with coarse-grained simulations to investigate the problems strongly influenced by the coupling of polymerization and excluded volume effects. Finally, a facile implementation of integrated tempering sampling method is illustrated to be very efficient on bypassing local energy minima and having access to true equilibrium polymer structures.

We present a mesoscale simulation model that is suitable for describing the deformable and non-centrosymmetric characteristics of soft triblock Janus particles. The model parameters are readily mapped onto experimental systems under different ambient conditions. We examine the influence of Janus balance and the flexibility of Janus particle aggregates on the packing structures. Some ordered structures, such as the hexagonal columnar structure and the body-centered tetragonal structure, are observed in our simulations. Our study demonstrates that the Janus balance and the flexibility of Janus particle aggregates can be tuned to obtain various ordered packing structures. The soft Janus particles with soft and deformable characteristics may bring new excitement to materials science.

How to create novel desired structures by rational design of building blocks represents a significant challenge in materials science. Here we report a conceptually new design principle for creating supracolloidal fullerene-like cages through the self-assembly of soft patchy particles interacting via directional nonbonded interactions by mimicking non-planar sp2 hybridized carbon atoms in C60. Our numerical investigations demonstrate that the rational design of patch configuration, size, and interaction can drive soft three-patch particles to reversibly self-assemble into a vast collection of supracolloidal fullerene-like cages. We further elucidate the formation mechanisms of supracolloidal fullerene-like cages by analyzing the structural characteristics and the formation process. Our results provide conceptual and practical guidance towards the experimental realization of supracolloidal fullerene-like cages, as well as a new perspective on understanding the fullerene formation mechanisms.

Existing conceptual design methods mainly focus on component modeling and representation, which makes them insufficient to help in the conceptual design stage. Port ontology, as an approach to formally expressing product design, has been effectively applied to concept description of a product. An incidence matrix support for product conceptual design based on port ontology is given in this paper. It formally represents and organizes product information in both functional ontology and physical domain in a hierarchy. Port compatibilities are used to map and link the two components. This makes it possible to build incidence matrix and decompose it into an independence matrix, and allow designers from different backgrounds with various interests to access the design ontology. A multilevel matrix is constructed to generate principle schemes of products at different levels of abstraction, which facilitates design decision-making through the whole conceptual design stage. A case study is also given to demonstrate the proposed approach.

A novel mesoscopic simulation method is adopted to study the ordered packing of the anisotropic disklike particles with a soft repulsive interaction, which possesses a modified anisotropic conservative force type used in dissipative particle dynamics. We examine the influence of the shape of the particles, the angular width of the repulsion, and the strength of the repulsion on the packing structures. Specifically, an ordered hexagonal columnar structure is obtained in our simulations. Our study demonstrates that an anisotropic repulsive potential between soft discoidal particles is sufficient to produce a relatively ordered hexagonal columnar structure.

Molecular dynamics simulations are adopted to calculate the equation of state characteristic parameters P*, rho*, and T* of isotactic polypropylene (iPP) and poly(ethylene-co-octene) (PEOC), which can be further used in the Sanchez-Lacombe lattice fluid theory (SLLFT) to describe the respective physical properties. The calculated T* is a function of the temperature, which was also found in the literature. To solve this problem, we propose a Boltzmann fitting of the data and obtain T* at the high-temperature limit. With these characteristic parameters, the pressure-volume-temperature (PVT) data of iPP and PEOC are predicted by the SLLFT equation of state. To justify the correctness of our results, we also obtain the PVT data for iPP and PEOC by experiments. Good agreement is found between the two sets of data. By integrating the Euler-Lagrange equation and the Cahn-Hilliard relation, we predict the density profiles and the surface tensions for iPP and PEOC, respectively. Furthermore, a recursive method is proposed to obtain the characteristic interaction energy parameter between iPP and PEOC. This method, which does not require fitting to the experimental phase equilibrium data, suggests an alternative way to predict the phase diagrams that are not easily obtained in experiments. As an example, in the framework of SLLFT, the spinodal curve for the iPP/PEOC blend is predicted at the low molecular weights that are used in the simulations.

We propose a simple and general mesoscale soft patchy particle model, which can felicitously describe the deformable and surface-anisotropic characteristics of soft patchy particles. This model can be used in dynamics simulations to investigate the aggregation behavior and mechanism of various types of soft patchy particles with tunable number, size, direction, and geometrical arrangement of the patches. To improve the computational efficiency of this mesoscale model in dynamics simulations, we give the simulation algorithm that fits the compute unified device architecture (CUDA) framework of NVIDIA graphics processing units (GPUs). The validation of the model and the performance of the simulations using GPUs are demonstrated by simulating several benchmark systems of soft patchy particles with 1 to 4 patches in a regular geometrical arrangement. Because of its simplicity and computational efficiency, the soft patchy particle model will provide a powerful tool to investigate the aggregation behavior of soft patchy particles, such as patchy micelles, patchy microgels, and patchy dendrimers, over larger spatial and temporal scales.

Patchy particles are a type of colloidal particles with one or more well-defined patches on the surfaces. The patchy particles with multiple compositions and functionalities have found wide applications from the fundamental studies to practical uses. In this research patchy micelles with thiol groups in the patches were prepared based on coassembly of free block copolymer chains and block copolymer brushes on silica particles. Thiol-terminated and cyanoisopropyl-capped polystyrene-block-poly(N-isopropylacrylamide) block copolymers (PS-b-PNIPAM-SH and PS-b-PNIPAM-CIP) were synthesized by reversible addition-fragmentation chain transfer polymerization and chemical modifications. Pyridyl disulfide-functionalized silica particles (SiO2-SS-Py) were prepared by four-step surface chemical reactions. PS-b-PNIPAM brushes on silica particles were prepared by thiol-disulfide exchange reaction between PS-b-PNIPAM-SH and SiO2-SS-Py. Surface micelles on silica particles were prepared by coassembly of PS-b-PNIPAM-CIP and block copolymer brushes. Upon cleavage of the surface micelles from silica particles, patchy micelles with thiol groups in the patches were obtained. Dynamic light scattering, transmission electron microscopy, and zeta-potential measurements demonstrate the preparation of patchy micelles. Gold nanoparticles can be anchored onto the patchy micelles through S-Au bonds, and asymmetric hybrid structures are formed. The thiol groups can be oxidized to disulfides, which results in directional assembly of the patchy micelles. The self-assembly behavior of the patchy micelles was studied experimentally and by computer simulation.

The design and fabrication of two-dimensional (2D) well-ordered nanostructures by a facile and effective strategy remain a major scientific and technological challenge, hitherto achieved mainly through the aid of interfaces or substrates with an ordered arrangement. Here we introduce a new concept in achieving template-free fabrication of diverse 2D ordered nanostructures by utilizing anisotropic characteristics of soft triblock Janus particles. Our numerical investigation demonstrates how particle softness and controllable directional attraction interplay to generate a number of fascinating non-close-packed 2D nanostructures and even three-dimensional (3D) vesicles. These non-close-packed nanostructures are of great interest for scientific reasons and lead to promising applications in soft nanotechnology and biotechnology.

GALAMOST [graphics processing unit (GPU)-accelerated large-scale molecular simulation toolkit] is a molecular simulation package designed to utilize the computational power of GPUs. Besides the common features of molecular dynamics (MD) packages, it is developed specially for the studies of self-assembly, phase transition, and other properties of polymeric systems at mesoscopic scale by using some lately developed simulation techniques. To accelerate the simulations, GALAMOST contains a hybrid particle-field MD technique where particle-particle interactions are replaced by interactions of particles with density fields. Moreover, the numerical potential obtained by bottom-up coarse-graining methods can be implemented in simulations with GALAMOST. By combining these force fields and particle-density coupling method in GALAMOST, the simulations for polymers can be performed with very large system sizes over long simulation time. In addition, GALAMOST encompasses two specific models, that is, a soft anisotropic particle model and a chain-growth polymerization model, by which the hierarchical self-assembly of soft anisotropic particles and the problems related to polymerization can be studied, respectively. The optimized algorithms implemented on the GPU, package characteristics, and benchmarks of GALAMOST are reported in detail. © 2013 Wiley Periodicals, Inc.

We develop a mesoscale nonequilibrium simulation model to study the effect of steady shear on the hierarchical self-assembly of soft disklike particles in dilute solutions. By properly tuning shear rates and solvent conditions, soft disklike particles can self-assemble into flexible threads and bundle-like structures along the flow direction. Shear flow facilitates the self-assembly of soft disklike particles into one-dimensional long threads along the flow direction; however, it suppresses the formation of flexible bundles from the threads while decreasing the solvent quality. The relatively well-defined bundle structures along the flow direction can only be obtained when the solvent condition becomes even worse. Our study elucidates how the solvent condition and shear rate can be utilized to control the shear-induced self-assembled structures, which would enable designed nanofabrication.

An image-based rendering method to separate specular and diffuse reflection elements in an image is presented. A method to reconstruct a new image with only the specular reflection effect by the separated results is further proposed using a neural network. The resulting virtual image is composed of the reconstructed specular and diffuse reflection images and is photo-realistic.