Nonperturbative effects of attraction on dynamical behaviors of glass-forming liquids

We investigate systematically the effects of the inter-particle attraction on the structure and dynamical behaviors of glass-forming liquids via molecular dynamics simulations.We find that the inter-particle attraction does not influence the structure,but greatly affects the dynamics and dynamical heterogeneity of the system.After the system changes from a purely repulsive glass-forming liquid to an attractive one,the dynamics slows down and the dynamical heterogeneity becomes greater,which is found interestingly to be associated with larger cooperative rearrangement regions(CRRs).Additionally,the structures of CRRs are observed to be compact in attractive glass-forming liquids but string-like in purely repulsive ones.Our findings constitute an important contribution to the ongoing study of the role of attractions in properties of glasses and glass-forming liquids.

Observation of the Pinning-Induced Crystal-Hexatic-Glass Transition in Two-Dimensional Colloidal Suspensions

Identification of the glass formation process in various conditions is of importance for fundamental understanding of the mechanism of glass transitions as well as for developments and applications of glassy materials.We investigate the role of pinning in driving the transformation of crystal into glass in two-dimensional colloidal suspensions of monodisperse microspheres.The pinning is produced by immobilizing a fraction of microspheres on the substrate of sample cells where the mobile microspheres sediment.Structurally,the crystal-hexatic-glass transition occurs with increasing the number fraction of pinningρpinning,and the orientational correlation exhibits a change from quasi-long-range to short-range order atρpinning=0.02.Interestingly,the dynamics shows a nonmonotonic change with increasing the fraction of pinning.This is due to the competition between the disorder that enhances the dynamics and the pinning that hinders the particle motions.Our work highlights the important role of the pinning on the colloidal glass transition,which not only provides a new strategy to prevent crystallization forming glass,but also is helpful for understanding of the vitrification in colloidal systems.

Adhesion of an Ultrasmall Nanoparticle on a Bilayer Membrane is Still Size and Shape Dependent

It has been found recently that an ultrasmall nanoparticle whose size is smaller than the thickness of a cell membrane has unique roles in biomedical applications including the development of next generation of drugs or advanced nanoscale cargo carriers.However,the effect of physical properties of an ultrasmall nanoparticle on its adhesion to a bilayer membrane,which is a key step for Nano-Bio interaction as well as the biomedical applications,is still largely unknown.By using molecular dynamics,we find that both size and shape of an ultrasmall nanoparticle strongly affect its adhesion states on a bilayer membrane(e.g.,adhesion,separation or entwined by polymer chains).Interestingly,our simulations show that with decreasing particle size,the effect of particle shape becomes even more evident for the adhesion behavior.It is indicated that the competition between nanoparticle-polymer binding and polymer chain deformation,both of which are influenced by particle size and shape,determines the final adhesion states of an ultrasmall nanoparticle.Our results are helpful for the full understanding of interaction mechanism between nanoparticles and cell membranes and the practical applications of such ultrasmall nanoparticles.

=unctional interlayer of PVDF-HFP and carbon nanofiber for long-life lithium-sulfur batteries

In the present work we develop a scalable and inexpensive design for lithium- sulfur （Li-S） batteries by capping a flexible gel polymer/carbon nanofiber （CNF） composite membrane onto a free-standing and binder-free CNF ＋ ni2s6 cathode, thus achieving a three-dimensional （3D） structural design. The CNF network is used as the current collector and S holder to overcome the insulating nature and volume expansion of S, while the composite membrane comprises a gel polymer poly（vinylidene fluoride-co-hexafluoropropylene） （PVDF-HFP）, and CNF additive is used as an interlayer to trap polysulfides and recycle the remaining S species, leading to a high specific capacity and long cycle life. This 3D structure enables excellent cyclability for 500 cycles at 0.5℃ with a small capacity decay of 0.092% per cycle. Furthermore, an outstanding cycle stability was also achieved at even higher current densities （1.0 to 2.0℃）, indicating its good potential for practical applications of Li-S batteries.

Non-equilibrium steady structures of confined liquid crystals driven by a dynamic boundary

Steady structures originating from dynamic self-assembly have begun to show their advantages in new generation materials, and pose challenges to equilibrium self-assembly. In view of the important role of confinement in self-assembly, here, we propose a new type of confinement leading to dynamic steady structures, which opens a new window for the conventional confinement.In our model, we consider the self-assembly of ellipsoids in 2D circular confinement via the boundary performing periodically stretching and contracting oscillation. Langevin dynamics simulations reveal the achievement of non-equilibrium steady structures under appropriate boundary motions, which are novel smectic structures with stable topological defects. Different from the confinement with a static boundary, ellipsoids close to the boundary have variable orientations depending on the boundary motion.Order-order structural transitions, accompanied by the symmetry change and varied defect number, occur with the change of oscillating amplitude and/or frequency of the boundary. Slow and fast dynamics are distinguished according to whether structural rearrangements and energetic adjustment happen or not. The collective motion of confined ellipsoids, aroused by the work performed on the system, is the key factor determining both the structure and dynamics of the self-assembly. Our results not only achieve novel textures of circular confined liquid crystals, but also inspire us to reconsider the self-assembly within the living organisms.

Spiral fractal patterns via hierarchical assembly

Chirality is ubiquitous in nature and manifested at various scale from subatom to galaxy.Fractal geometry is also very popular and active in the world.However,there are few reports on the concept of combining fractal patterns and chiral structures in self-assembled systems.It was found that tree-shaped fractal patterns could be self-assembled from the N-[(9H-fluoren-9-ylmethoxy)carbonyl]protected glutamic acid(Fmoc-Glu)and zinc-porphyrin(ZnTPyP).The fractal pattern was composed of nanorod aggregate arranged in a spiral fractal way,in which the nanorods were stacked one-by-one in a single direction.The patterns started with the formation of initial nucleon and growing,during which the diffusion limited aggregation(DLA)mechanism led to the fractal patterns.Interestingly,the spiral packing and their branches were closely related to the absolute configuration of Fmoc-Glu that anticlockwise and clockwise arrangement for L-Fmoc-Glu/ZnTPyP and D-Fmoc-Glu/ZnTPyP,respectively.Our work provides a new finding on the spiral fractal pattern via hierarchical self-assembly.