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Polar groups have long been recognized to greatly influence the glass transition temperature (Tg) of polymers, but understanding the underlying physical mechanism remains a challenge.

Morphological and rheological properties are examined for poly(styrene-co-2-vinyl pyridine) (P(S-co-2VP)) copolymers upon introducing phosphotungstic acid, one kind of polyoxometalates (POMs). The phosphotungstic acid protonates the 2VP monomers, and the deprotonated phosphotungstic acid effectively crosslinks the protonated 2VP monomers, inducing phase segregation into the S-rich and 2VP-rich domains. Linear viscoelasticity (LVE) of the composite samples strongly relies on the continuity of the 2VP-rich domains and can be classified into the following three types. (1) For 2VP-rich sphere domains in the S-rich matrix, LVE is akin to the conventional elastomer characterized by a wide rubbery regime before the terminal relaxation. (2) For bicontinuous morphology, where both the 2VP-rich and S-rich domains are continuous, two glassy processes manifest in LVE, and the chain relaxation is controlled by the continuous ion dissociation in the less mobilized 2VP-rich domain. (3) When the 2VP-rich domain is the only continuous phase, only the glassy modulus of the 2VP-rich domain manifests in LVE, and the chain relaxation is activated by the continuous ionic dissociations in the matrix. Surprisingly, the relaxation time obtained for all three abovementioned morphologies can be reduced to a universal behavior once the average glass transition temperature of the 2VP-rich region and the number of effective stickers per chain have been properly normalized, indicating that these two parameters control the chain-dimensional dynamics.

Synthetic polymer single-chain nanoparticles (SCNPs) are an emerging new class of nanomaterials that possess similar folded structures as natural proteins. However, most SCNPs reported so far are p...

We use coarse-grained molecular dynamics simulations to study the self-assembly behavior of polyoxometalate (POM) nanoparticles (NPs) decorated with mobile polymer ligands under melt conditions. We demonstrate that due to the mobile nature of the grafted ligands on the NP surface, NPs have the ability to expose a part of their surfaces, leading to a block-copolymer-like self-assembly behavior. The exposed NP surface serves as one block and the grafted ligand polymers as another. This system has a strong ability to self-assemble into long-range ordered structures such as block copolymers due to large incompatibility between POM and ligand polymers, i.e., POM NPs can form lamellar, cylindrical, and spherical structures, which are consistent with previous experimental results. More importantly, these ordered structures are on the sub-10 nm scale, which is an important requirement for many applications. At low graft density, we find a new inverse-cylindrical structure formation where polymers form cylinders and POMs form a continuous network structure. A full self-assembly phase diagram is constructed which illustrates rules to manipulate the self-assembly structures of NPs decorated with mobile polymer ligands. We hope that these computational results will be useful for the new design of nanostructures with improved optical or electronic functions.

Modern electrochemical and electronic devices require advanced electrolytes. Liquid crystals have emerged as promising electrolyte candidates due to their good fluidity and long-range order. However, the mesophase of liquid crystals is variable upon heating, which limits their applications as high-temperature electrolytes, e.g., implementing anhydrous proton conduction above 100 °C. Here, we report a highly stable thermotropic liquid-crystalline electrolyte based on the electrostatic self-assembly of polyoxometalate (POM) clusters and zwitterionic polymer ligands. These electrolytes can form a well-ordered mesophase with sub-10 nm POM-based columnar domains, attributed to the dynamic rearrangement of polymer ligands on POM surfaces. Notably, POMs can serve as both electrostatic cross-linkers and high proton conductors, which enable the columnar domains to be high-temperature-stable channels for anhydrous proton conduction. These nanochannels can maintain constant columnar structures in a wide temperature range from 90 to 160 °C. This work demonstrates the unique role of POMs in developing high-performance liquid-crystalline electrolytes, which can provide a new route to design advanced ion transport systems for energy and electronic applications.

Incorporating nanoparticles (NPs) into polymers is a practical method to tune the mechanical properties of the material. In such composite systems, it is well accepted that the interface properties...

By using coarse-grained molecular dynamics simulations, we have investigated the structure and dynamics of supercooled single-chain cross-linked nanoparticle (SCNP) melts having a range of cross-linking degrees ϕ. We find a nearly linear increase in glass-transition temperature (Tg) with increasing ϕ. Correspondingly, we have also experimentally synthesized a series of polystyrene-based SCNPs and have found that the measured Tg estimated from differential scanning calorimetry is qualitatively consistent with the trend predicted by our simulation estimates. Experimentally, an increase in Tg as large as ΔTg = 61 K for ϕ = 0.36 is found compared with their linear chain counterparts, indicating that the changes in dynamics with cross-links are quite appreciable. We attribute the increase in Tg to the enlarged effective hard-core volume and the corresponding reduction in the free volume of the polymer segments. Topological constraints evidently frustrate the local packing. In addition, the introduction of intra-molecular cross-linking bonds slows down the structural relaxation and simultaneously enhances the local coupling motion on the length scales within SCNPs. Consequently, a more pronounced dynamical heterogeneity (DH) is observed for larger ϕ, as quantified by measuring the dynamical correlation length through the four-point susceptibility parameter, χ4. The increase in DH is directly related to the enhanced local cooperative motion derived from intra-molecular cross-linking bonds and structural heterogeneity derived from the cross-linking process. These results shed new light on the influence of intra-molecular topological constraints on the segmental dynamics of polymer melts.

The formation of polymer-patch nanoparticles (PNPs) involves a condensation process of grafted chains on a nanoparticle (NP) surface, which is conventionally achieved via a fine-tuning of the solvent quality. However, such a critical solvent condition differs dramatically between polymers, and the formation mechanism of different patchy structures remains under debate. In this study, we demonstrate by a combined simulation and experimental study that such a surface-patterning process can be easily achieved via a simple solvent evaporation process, which creates a natural nonsolvent condition and is, in principle, adaptable for all polymers. More importantly, we find that patchy structures are controlled by a delicate balance between enthalpic interaction and the entropy penalty of grafted chains. A small variation of cohesive energy density can lead to a dramatic change in patch structure. This work offers a robust yet easy approach for the fabrication of PNPs and provides new insights into polymer segregation on spherical surfaces.

We study the interfacial structure and dynamics of a polymer nanocomposite (PNC) composed of octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and poly(2-vinylpyridine) (P2VP) by performing full atomistic molecular dynamics simulations. There are eight aminophenyl groups grafted on the surface of the OAPS particle and the particle has a size comparable to the Kuhn segment of P2VP. These aminophenyl groups can form hydrogen bonds (HBs) with pyridine rings from surrounding P2VP chains. We found that OAPS can form ∼2 HBs on average with surrounding polymer chains. The effect of the HBs is investigated in detail by either switching on or off these HBs in our simulation. By analyzing the interfacial static packing structure and dynamic properties, we demonstrate that the system has an ∼1 nm interface width, similar to the OAPS particle size. We also found that HBs can prevent the further penetration of polymers into the inner zone (grafting layer) of the OAPS, and therefore keep the P2VP chains in the outer layer (>1 nm), remaining bulk-like, which is well consistent with experimental results. In addition, we found that NP diffusion is coupled to the absorbed polymer chains, which also dramatically slows down the diffusion of polymer segments in return. The core–shell model in which the NP and absorbed polymers diffuse as a single object is validated here at the full atomistic level. These results provide atomistic insights into the unique structure and dynamics in the small attractive NP–polymer interfacial region. We hope these results will be helpful for the understanding of peculiar phenomena in attractive polymer nanocomposites containing small NPs.

Since the discovery of amorphous red phosphorus (a-red P) in 1847, many possible structures have been proposed. However, the exact molecular structure has not yet been determined because of its amorphous nature. Herein several methods are used to investigate basic properties of a-red P. Data from scanning tunneling microscopy (STM) and gel permeation chromatography (GPC) confirm that a-red P is a linear inorganic polymer with a broad molecular weight distribution. The theoretical single-molecule elasticities of the possible a-red P structures are obtained by quantum mechanical (QM) calculations. The experimental single-molecule elasticity of a-red P measured by single-molecule AFM matches with the theoretical result of the zig-zag ladder structure, indicating that a-red P may adopt this structure. Although this conclusion needs further validation, this fundamental study represents progress towards solving the structure of a-red P. It is expected that the strategy utilized in this work can be applied to study other inorganic polymers.

Vitrimers with dynamic covalent bonds make thermosetting materials plastic, recyclable and self-repairing, and have broad application prospects. However, due to the complex composition of vitrimers and the dynamic bond exchange reactions (BERs), the mechanism behind their unique dynamic behavior is not fully understood. We used the hybrid molecular dynamics-Monte Carlo (MD-MC) algorithm to establish a molecular dynamics model that can accurately reflect BERs, and reveal the intrinsic mechanism of the dynamic behavior of the vitrimer system. The simulation results show that BERs change the diffusion mode of the vitrimer's constituent molecules, which in turn affects the BER and other relaxation dynamics. This provides a theoretical basis and a specific method for the rational design of the rheological properties of vitrimers.

It is widely accepted that adding nanoparticles (NPs) into polymer matrices can dramatically alter the mechanical properties of the material, and that the properties at the NP/polymer interface play a vital role. By performing coarse-grained molecular dynamics simulations, we study the stress-strain behaviour of polymer/NP composites (PNCs) in a glassy state under a triaxial tensile deformation, in which the NPs are well dispersed in the system via bimodal grafting. A 'HOMO' system, in which the short grafted chains are chemically identical to the matrix polymer, and a 'HETERO' system, in which the short grafted chains interact weakly with the matrix, are investigated. Our simulations demonstrate that the HOMO system behaves very similarly to the pure polymer system, with quick cavitation and a drop in stress after the yielding point, corresponding to a craze deformation process. While in the HETERO system, weak interactions between the short grafts and the matrix polymer induce a low local modulus, therefore, rather homogeneous void formation and consequently a slower cavitation process are observed at the surface of the well dispersed NPs during the tensile deformation. As a result, the depletion effect at the NP surface eventually leads to NP re-assembly at large strains. Moreover, the HETERO system undergoes a shear-deformation-tended tensile process rather than the craze deformation found in the HOMO system. At the same time, the HETERO system is more ductile, with a much slower drop in stress after yielding than the HOMO system. In addition, the homogeneous generation of voids at small strain in the HETERO system can be utilized in the fabrication of polymer films with desirable separation abilities for gases or small molecules. We hope that these simulation results will be helpful for the property regulation of PNC materials containing polymer grafted NPs.

We demonstrate that polymer number distribution (PND) for polymer grafted nanoparticles (NPs) fabricated via the grafting-to technique can be described, without any fitting parameters, as a function of the conversion of polymer chains. This distribution function is convenient to be applied since the variables in PND are directly linked to experimental measurements and easy to be obtained. As an independent validation, the molecular dynamics simulation in this study is important since the experimental approach may be prone to artifacts that result from the complex parameters. This distribution is further generalized to describe the PNDs for polymer grafted NPs fabricated via the grafting-from technique. Our study implies that the grafting process, no matter grafting-to or grafting-from, does not alter the heterogeneity. Our results also provide evidence that the Poisson model, often invoked to describe the PND in previous experiments, is not accurate. We also show that the binomial form function of PND wil...

An efficient calculation of NFFT (nonequispaced fast Fourier transforms) is always a challenging task in a variety of application areas, from medical imaging to radio astronomy to chemical simulation. In this article, a new theoretical derivation is proposed for NFFT based on gridding algorithm and new strategies are proposed for the implementation of both forward NFFT and its inverse on both CPU and GPU. The GPU-based version, namely CUNFFT, adopts CUDA (Compute Unified Device Architecture) technology, which supports a fine-grained parallel computing scheme. The approximation errors introduced in the algorithm are discussed with respect to different window functions. Finally, benchmark calculations are executed to illustrate the accuracy and performance of NFFT and CUNFFT. The results show that CUNFFT is not only with high accuracy, but also substantially faster than conventional NFFT on CPU.

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-...

Diffusion dynamics of nanoparticles in polymer nanocomposites is investigated by coarse-grained molecular dynamics simulations. We report a strong polymer chain length dependent non-Gaussian diffusion of nanoparticles (NPs) in entangled polymer melt. By analyzing the NP motion and the polymer relaxation at different length and time scales, we find that the non-Gaussian diffusion of NPs originates from a dynamic coupling at a specific length scale with the melt polymer chain segments that possess similar size with NP. Our results provide a microscopic understanding of the complex particle environment interactions and a detailed mechanism for nanoparticle diffusion in entangled polymer melt.

Polymer based nanocontainers have attracted a myriad of interests due to their functional groups, mechanical stability, combining with inner voids and large specific surface area. Preparation of polymer nanocontainers with specific nonspherical geometric morphology, precisely controllable structure, composition, and functionalities still remains a significant challenge. Here, we report a method that enables synthesizing nonspherical polymer nanocontainers with different morphologies and properties by using anisotropic metal–organic coordination compounds as templates. The preparation process is based on the stronger monomer’s binding ability to metal cations than that to the organic linkers. The correlation between the binding energy and the formation of the hollow structure is calculated theoretically. Polymer nanocontainers with multiple morphologies (such as octahedron, dodecahedron, etc.) are constructed by expanding template materials. The as-prepared polymer nanocontainers exhibit active properties ...

In this work, dissipative particle dynamics simulations are carried out to investigate the phase behaviour of cyclic c-AB diblock copolymers with different designed dispersities in molecular weight...

It is well known that the presence of nanoparticles in polymer melt can dramatically influence the dynamics of the polymers. Here from a molecular dynamics simulation study, we find that such influences can be largely temperature dependent in a polymer/single chain nanoparticle composite. At high temperature, the translational diffusion of polymers can be accelerated due to large deformability of nanoparticle surface. While when temperature decreases, nanoparticle surface deformability decreases dramatically and therefore nanoparticles can impose large excess free energy barrier on polymer diffusion. As a consequence, the diffusion of polymers at low temperature can be largely decelerated.

Here we report a quantum mechanical molecular dynamics (QM/MD) study of a fusion process of an open-ended carbon nanotube on a graphene hole, which results in the formation of a so-called pillared graphene structure – a three-dimensional nanomaterial consisting entirely of sp2-carbons. The self-consistent-charge density-functional tight-binding potential was adopted in this study. Two different sizes of graphene holes with 12 or 24 central carbon atoms removed from a graphene flake, and a (6,6) carbon nanotube with a compatible diameter were adopted. Formations of 6–7–6/5–8–5 defect structures were found on the fusion border between tube and graphene hole. The 6–7–6 structure was found to bear less curvature-induced strain energy and therefore to be more stable and much easier to form than the 5–8–5 structure.

After the discovery of the highly symmetric Buckminsterfullerene (BF), a major goal of the fullerene community has been to understand its formation mechanism. In the various mechanisms proposed in literature, BF forms by either a bottom-up only or a top-down only process. Here we present a comprehensive quantum mechanical molecular dynamics simulation study, that reports for the first time the observations of multiple icosahedral symmetric Ih-C60 cages formations at the atomic level. Our simulation results demonstrate that helium atoms can not only reduce the temperature of the carbon species, but more importantly they can dramatically influence the reaction dynamics and eventually the fullerene yield through thermal collisions with carbon species. The direct evidence for coexistence of both bottom-up and top-down mechanisms are shown. Interestingly, rather than ceasing magically at C60, a similar process also applies to the formation of larger or smaller fullerenes. Prolonged vacuum annealing simulations show a typical top-down process where shrinking and surface healing of defective cages can enhance the Ih-C60 yield. Our results shed new light on the fundamental BF formation process in graphite laser ablation, in carbon arc-discharge experiments, as well as in the interstellar space.

This editorial discusses the broad range and scope of this special issue of Soft Materials. All articles deal with the challenge to model and/or simulate various types of systems of soft matter. De...

Dynamic heterogeneity (DH) is a universal property of glass transition phenomena. In this work, we perform a comparative analysis of DH for pure polymer and polymer/nanoparticle composite systems in both film and bulk states via molecular dynamics simulations. We find that the dynamic gradient and the faster average dynamics due to the presence of a free surface are two leading factors, resulting from a nanoconfinement effect, which influence different parts of DH in a film system. The dynamic gradient results from differences in dynamics at different distances from the mobile surface, which induces a large deviation from the Gaussian distribution for the displacement distribution in the film. At the same time, the maximum string size which describes the region size for cooperative motion (dynamic correlation) can also be influenced by the dynamic gradient, although this influence is much weaker than that on the displacement distribution. On the other hand, reflecting temporal fluctuations of dynamics or temporal parts of DH, characteristic peak times of the non-Gaussian parameter and string size, and the ratio between persistent times and exchange times which describe the dynamic exchange properties, are mainly influenced by the faster dynamics on average. Our results demonstrate that measuring different properties (dynamic distribution, dynamic correlation or dynamic exchange) place an emphasis on distinct temporal and spatial parts of DH. It is necessary to use combinational measurements of these properties to give a complete picture of DH in nanoconfinement environments.

Multiscale hierarchical morphologies are greatly desired for fabricating nanocomposites with tunable macroscopic properties, but challenges remain in precisely manipulating the spatial arrangement of nanoparticles in polymer matrices across multiple length scales. Here, we demonstrate a class of mobile-ligand nanoparticle system built upon 1 nm anionic polyoxometalate molecular nanoparticles and cationic terminated polymer chains by electrostatic interaction. The highly rearrangeable polymer chains can serve as mobile ligands to direct the polyoxometalates to align into sub-10 nm anisotropic superlattice-like nanoarrays in the bulk state. Moreover, these nanoarrays can further serve as structural units to assemble into hierarchically ordered morphologies in polymer matrices, e.g., percolated networks over hundreds of micrometers which are comprised of cylindrically packed polyoxometalate superlattices down to sub-10 nm scale. These hierarchical morphologies enable the nanocomposites with reinforced mechanical performance. The presented mobile-ligand approach can provide a paradigm to design functional polymer nanocomposites with improved properties such as mechanical reinforcement and collective optical and electronic functions.

In polymer/nanoparticle composite (PNC) thin films, polymer chains experience strong confinement effects not only at the free surface area but also from nanoparticles (NPs). In this work, the influence of NP–polymer interaction and NP distribution on the polymer segmental dynamics and the glass transition behavior of PNC free-standing films are investigated through molecular dynamics simulations. We demonstrate that NPs will migrate to the film surface area and form an NP-concentrated layer when NP–polymer interactions are weak, while NPs are well dispersed in the bulk region when NP–polymer interactions are strong. In both cases, we find increases in the glass transition temperature Tg compared with the pure film without NPs, although with a different degree. The weakly interacting system has the same Tg as the pure bulk system without NPs. The NP layer formed at the surface area reduces both the mobility of the surface polymer beads and the mobility gradient in the film normal direction (MGFND), therefore resulting in an increase in the Tg which highlights the vital role of the mobile surface layer. In contrast, the NPs in the bulk region enlarge the MGFND. NPs have opposite influences on the polymer bead dynamic anisotropy when they interact weakly or strongly with polymers, weakened for the former and enhanced for the latter. These findings offer a clear picture of the segmental dynamics and glass transition behavior in free-standing PNC films with different NP–polymer interaction strengths. We hope these results will be helpful for the property design of related materials.

The controllable distribution of nanoparticles (NPs) in polymer nanocomposites (PNCs) is a challenge in materials science. An important method is grafting chains that are chemically identical to the polymer matrix on NPs. By performing comprehensive molecular dynamics simulations, the self-assembly behavior of polymer-grafted NPs in a polymer matrix is investigated in this study. The relationship between the grafted chain length N, grafting density σ and the NPs' self-assembly morphologies is studied. Phase diagrams of the NP self-assembly structures for both unimodal and bimodal grafted NP systems are constructed on a parameter space, where P is the matrix polymer chain length. NP self-assembly structures of strings, connected/sheet and small clusters are identified in different regions. In order to quantitatively characterize the NP self-assembly morphology, we define a morphological measurement parameter which characterizes the distribution of the Voronoi cell volume of the NPs. Using this parameter, we discuss the influences of both long and short grafted chains on the dispersion of bimodal polymer-grafted NPs in a polymer melt. We find that the short grafted chains can not only shield the NP surface from the polymer matrix but also elongate the long grafted chains into the polymer matrix, therefore favoring a better dispersion of NPs. Our results also indicate that the bimodal grafted NPs will not be fully dispersed until the short grafted chains are dense enough to elongate the long grafted chains, hence forming a wetting NP/matrix interface.

Recent progress in producing short chain length diblock copolymers facilitates the fabrication of block copolymer nanostructures with extremely small feature sizes. In this work, phase diagrams for monodisperse, one-sided and two-sided polydisperse short diblock copolymer melts are constructed using dissipative particle dynamics (DPD) simulations. Detailed comparisons are carried out between these systems to elucidate the influence of chain length polydispersity on the phase behavior of short diblock copolymers. In particular, we find an unexpected stability of a bicontinuous structure over a wide composition range between 0.7

Block copolymers have the unique property to self-assemble into ordered microstructures with well-defined periodicity. Among the various attainable microdomain morphologies, complex morphologies with inherent structural connectivity are highly desirable. While such structures are difficult to obtain in monodisperse block copolymers, they may be stabilized by increasing block dispersity. In this study, we prepare poly (styrene-b-methyl methacrylate) (PS-b-PMMA) diblock copolymers where dispersity of both PS and PMMA blocks are varied independently. Morphology examination of the diblocks reveals that at fixed block composition, dispersity dictated phase transition is observed. In particular, in the case where dispersity of both blocks are high, the polymers are found to exhibit perforated lamellae and disordered bicontinuous morphologies. Dissipative particle dynamics (DPD) simulations are also carried out to confirm the stability of the observed morphologies. These results show that control of block dispersity can effectively stabilize energetically disfavored complex morphologies in block copolymers.

Patchy nanoparticles (PNPs) have received increased attention since they serve as a new type of self-assembly unit. However, the precise synthesis of PNPs with target patch numbers and their spatial distribution on a nanoparticle (NP) surface are still a formidable challenge. A recent experimental study [R. M. Choueiri et al., Nature, 2016, 538, 79] has demonstrated that following a change in the solvent quality, the collapse and thermodynamically driven segregation of the grafted homopolymer (HP) chains on the NP surface can lead to the formation of surface-pinned micelles, and therefore, PNPs. In this study, by using coarse-grained molecular dynamics simulations, we demonstrate that the collapse of the grafted diblock copolymer (DBC) chains on the NP surface can also lead to the formation of PNPs, but in a more controllable manner with target patch numbers and symmetric surface distribution. In addition, our studies have shown that PNPs formed from the collapse of surface-grafted DBC chains are superior to those formed from the collapse of HP chains. We have shown that the use of DBC can generate more spherical patches than that using HP. More importantly, grafting DBC chains on the NP surface offers a larger adjustable parameter space due to their distinct properties, tunable volume fractions of the two blocks, and the different interaction types with the NP surface. In addition, solvent-phobicity and the sequence of collapsing of each block can also be utilized to control the formation pathway of the PNP structures.

Polymeric single-chain nanoparticles (SCNPs) are soft nano-objects synthesized by intramolecular crosslinking of isolated single polymer chains. Syntheses of such SCNPs usually need to be performed in a dilute solution. In such a condition, the bonding probability of the two active crosslinking units at a short contour distance along the chain backbone is much higher than those which are far away from each other. Such a reaction condition often results in local spheroidization and, therefore, the formation of loosely packed structures. How to inhibit the local spheroidization and improve the compactness of SCNPs is thus a major challenge for the syntheses of SCNPs. In this study, computer simulations are performed and the fact that a precollapse of the polymer chain conformation in a cosolvent condition can largely improve the probability of the crosslinking reactions at large contour distances is demonstrated, favoring the formations of closely packed globular structures. As a result, the formed SCNPs can be more spherical and have higher compactness than those fabricated in ultradilute good solvent solution in a conventional way. It is believed this simulation work can provide a insight into the effective syntheses of SCNPs with spherical conformations and high compactness.

The diffusion dynamics of fullerene (C 60 ) in unentangled linear atactic polystyrene (PS) and polypropylene (PP) melts and the structure and dynamic properties of polymers in interface area are investigated by performing all-atom molecular dynamics simulations. The comparison of the results in two systems emphasises the influence of local interactions exerted by polymer side group on the diffusion dynamics of the nanoparticle. In the normal diffusive regime at long time scales, the displacement distribution function (DDF) follows a Gaussian distribution in PP system, indicating a normal diffusion of C 60 . However, we observe multiple peaks in the DDF curve for C 60 diffusing in PS melt, which indicates a diffusion mechanism of hopping of C 60 . The attractive interaction between C 60 and phenyl ring side groups are found to be responsible for the observed hopping diffusion. In addition, we find that the C 60 is dynamically coupled with a subsection of a tetramer on PS chain, which has a similar size with C 60 . The phenyl ring on PS chain backbone tends to have a parallel configuration in the vicinity of C 60 surface, therefore neighbouring phenyl rings can form chelation effect on the C 60 surface. Consequently, the rotational dynamics of phenyl ring and the translational diffusion of styrene monomers are found to be slowed down in this interface area. We hope our results can be helpful for understanding of the influence of the local interactions on the nanoparticle diffusion dynamics and interfacial properties in polymer/nanoparticle composites.

Quantum chemical molecular dynamics simulations of graphene growth from small island precursors in different carbon nucleation densities on the Ni(111) surface at high temperatures have been conducted. The results indicate that small islands are not static, i.e. lateral diffusion and vertical fluctuation are frequently observed. In the case of low carbon nucleation density, carbon atoms or small carbon patches diffuse and attach to the edge of the nuclei to expand the size of the growing carbon network. The growth of graphene precursors is accompanied by the corresponding changes in the bonding of nickel atoms with the precipitation of subsurface carbon atoms. This is because the carbon-carbon interaction is stronger than the nickel-carbon interaction. In the case of high carbon nucleation densities, the dominant ripening mechanism depends on different growth stages. In the initial stage, the coalescence of carbon islands takes place via the Smoluchowski ripening mechanism. In the later stage the Smoluchowski ripening process is damped owing to the higher diffusion barrier of larger clusters and the restriction of movement by self-assembled nickel step edges. The cross-linking mechanism eventually takes over by the coalescence of extended polyyne chains between graphene islands. In either case, the Ostwald ripening process is not found in our molecular dynamics simulations due to the stability of carbon-carbon bonds within the islands. These investigations should be instructive to the control of graphene growth in experiments.

The coassembly of block copolymers (BCPs) with nanoscale inorganic objects is an important route to fabricate nanostructured polymer composites. However, the immiscibility of inorganic/polymeric interface is a recurring challenge to overcome, particularly for inorganic clusters, such as the polyoxometalates (POMs)/BCPs system. In this paper, we present a general method to incorporate POMs into BCP matrices, in which a POM cluster is embedded as a core in a supramolecular star polymer (SSP) whose arms possess the same chemical composition as a BCP segment. Because of the enthalpic interaction between SSP arms and BCP segments, the SSP can carry POM into BCP matrices to realize their coassembly. By this way, we successfully localize a Keggin-type POM cluster [CoW12O40]6– modified with polystyrene (PS) arms into the PS domain of poly(styrene-b-ethylene oxide) micelles, which induces the formation of a series of hybrid micelles with spherical, toroidal, and bicontinuous structures. The morphological transitio...

Natural cellulose (NC) is the most abundant biomacromolecule. The fact that each pyranose ring of NC has three hydroxyl groups implies that NC should be highly hydrophilic. The paradoxical water insolubility of NC is usually explained by the strong tendency to form the hydrogen-bonding network by the high content of hydroxyl groups. In this study, we present the first experimental evidence that NC is rather hydrophobic, even if the chains are molecularly dispersed. By single-molecule force spectroscopy, the single-chain mechanics of NC has been studied in various liquid environments. In a common nonpolar solvent, octane, NC shows the elastic force–extension (F–E) curve. We find that this kind of F–E curve can be fitted well by the QM-FJC model, in which the single-chain elasticity obtained from quantum mechanical (QM) calculations is integrated into the freely jointed-chain (FJC) model. However, the result of NC obtained in water is different, which shows a long plateau in the F–E curve. Further study sho...

It is crucial to understand how much and how far the structure and dynamics properties of the polymer melt can be affected by incorporating nanoparticles (NPs) in the system. Here, we show that in an athermal all-polymer nanocomposites prepared from mixtures of linear polystyrene chains and cross-linked polystyrene NPs, the influence range of the NP on the melt polymer properties, namely interphase thickness, depends on the properties investigated. The local segment conformations can be affected in the range of an NP radius. However, if the interphase thickness is defined by the influence range of the NP on the radius of gyration (Rg) of the melt chain, it can be 1.5Rg for short-chain melts where the chain has a Rg smaller than particle radius Ra. For intermediate chain length polymer melts (Rg > Ra), the influence range of the NP does not change with the chain length. With the chain length further increasing, melt chains cannot feel the existence of the NP; the influence of the NP on the Rg tensors of th...