原纤化Lyocell纤维/聚乳酸复合材料的结构与性能

采用均质分散法制备原纤化Lyocell纤维,探讨了不同初始纤维长度对Lyocell纤维原纤化程度的影响,在此基础上,进一步通过熔融共混和注塑成型制备原纤化Lyocell/聚乳酸(PLA)复合材料,探讨了初始纤维长度对原纤化Lyocell/PLA复合材料结构与性能的影响。结果表明,相同处理条件下,纤维初始长度越长,Lyocell纤维原纤化程度越低。Lyocell纤维原纤化能改善纤维与基体的界面结合,从而进一步提高复合材料的力学性能。初始纤维长度对原纤化Lyocell/PLA复合材料的拉伸性能无显著影响,而初始长度为4 mm的原纤化Lyocell/PLA复合材料的缺口冲击强度最大,比未原纤化复合材料提高19.0%。此外,Lyocell原纤化后还可进一步提高复合材料的维卡软化温度,当纤维初始长度为10 mm时,原纤化Lyocell/PLA复合材料的维卡软化温度最高,达到161.4℃。

Atomic insights into synergistic effect of pillared graphene by carbon nanotube on the mechanical properties of polymer nanocomposites

Molecular dynamics simulations have been performed to explore the underlying synergistic mechanism of pillared graphene or non-covalent connected graphene and carbon nanotubes(CNTs) on the mechanical properties of polyethylene(PE) nanocomposites. By constructing the pillared graphene model and CNTs/graphene model, the effect of the structure, arrangement and dispersion of hybrid fillers on the tensile mechanical properties of PE nanocomposites was studied. The results show that the pillared graphene/PE nanocomposites exhibit higher Young’s modulus, tensile strength and elongation at break than non-covalent connected CNTs/graphene/PE nanocomposites. The pull-out simulations show that pillared graphene by CNTs has both large interfacial load and long displacement due to the mixed modes of shear separation and normal separation. Additionally, pillared graphene can not only inhibit agglomeration but also form a compact effective thickness(stiff layer), consistent with the adsorption behavior and improved interfacial energy between pillared graphene and PE matrix.

Synthesis of a Highly Crystalline Amide-Linked Covalent Organic Framework

The dilemma for the synthesis of covalent organic frameworks(COFs)is crystallinity and stability.Herein,we present the synthesis of a single-crystalline amide-linked COF,and demonstrate its excellent chemical as well as thermal stabilities.This study will inspire the synthesis of a wide spectrum of highly crystalline and stable COFs,promote their structure-property investigations and boost their applications in selective gas adsorption,storage and separation.

On Water Growth of Continuous Thin Films of Two-Dimensional Covalent Organic Frameworks with Large Single-Crystal Domains

A core feature of two-dimensional covalent organic frameworks is crystallinity, but it remains challenging to gain their thin films with high crystallinity. Here, we presented growth of thin films of two-dimensional covalent organic frameworks with an average domain size of ~2.83 μm^(2) and maximum domain size of up to ~26.19 μm^(2) using amphiphilic glycine derivatives on water surface. We envisage that this work will inspire the growth of a wide variety of organic two-dimensional materials with high crystallinity and boost their structure property investigations.

Synthesis and Structure of the Inclusion Compound COF300-ALA

Background and Originality Content,Inclusion single crystals(IsCs)are characterized by the encapsulation of guest molecules within the crystal lattice of a host framework,resulting in,well-defined channels or cavities throughout the material. Host molecules can be broadly di.Videdinto wo main categories.i)The more widespreadgroup is unimolecular inclusion compounds where one host molecule interacts with one guest species.Familiar examples of this cate-gory include calixarenes,cyclodextrins,crown ethers,bai cavitands.cucurbituils,uoaciyclophanes,and various carcerands,ii) the other is multimoiecular inclusion caompounds where two or more host molecules are involved in forming cavities,channels,or layers in the crystal structure to accommodate guest molecules.Host molecules of,this kind include urea,choleic acis,Dianin's compound,etc.,and crystline porous materials such as metal-organic poliyhedrali and porous organic[18]cagesll are well-known examples.

Synthesis of Thin Film of a Three-Dimensional Covalent Organic Framework as Anti-counterfeiting Label

Film plays a key role in the sustainable development of our society.Freestanding thin films of two-dimensional covalent organic frameworks(coFs)have been produced by interface,spin coating,microwave-assisted synthesis,and screen printing methods and are applied in nanofitration,molecular separation,photochemical sensing,anion transport,heat conduction,and proton conduction.On the other hand,the synthesis of their three-dimensional(3D)analogues and subsequent integration in devices remains challenging.Herein,self-supporting thin films of a three-dimensionai COF with tunable thickness was created by a stearic acid mediated synthesis methodology on water surface at room temperature in air.The film could be transferred onto arbitrary substrate,and when supported on indium tin oxide glass,it exhibited irreversible electrochromism.The optical feature made it act as a one-time anti-counterfeiting label in an electrochemical device.This work will inspire the synthesis of thin films of 3D COFs as well as other 3D materials,and boost their property and application exploration.

Aqueous Synthesis of Covalent Organic Frameworks as Photocatalysts for Hydrogen Peroxide Production

Covalent organic frameworks(COFs)are crystalline porous polymers with designable structures and properties.Their crystallization typically relies on trialand-error experimentation involving harsh conditions,including organic solvents,presenting significant obstacles for rational design and large-scale production.Herein,we present a liquid crystal-directed synthesis methodology and its implementation for up to gram-scale production of highly crystalline COFs in water and air.It is compatible with monomers of different structures,shape,size,length of side chains,and electron-donating,electron-accepting,and heterocyclic substitutions near reactive sites.Seventeen types of donor-acceptor two-dimensional COFs including four types of new ones and a three-dimensional COF with a yield of up to 94%were demonstrated,showing great generality of the method.The as-synthesized donor-acceptor COFs are organic semiconductors and contain macropores besides intrinsic mesopores which make them attractive catalysts.The production of H_(2)O_(2)under visible light in water was studied and the structure-property relationships were revealed.The production rate reached 4347μmol h^(−1)gcat^(−1),which is about 467%better than that of the benchmark photocatalyst g-C_(3)N_(4).This study will inspire the mild synthesis and scale-up of a wide spectrum of COFs and organic semiconductors as efficient catalysts,promote their structure-property investigation,and boost their applications.

Towards robustness and generalization of point cloud representation:A geometry coding method and a large-scale object-level dataset

Robustness and generalization are two challenging problems for learning point cloud representation.To tackle these problems,we first design a novel geometry coding model,which can effectively use an invariant eigengraph to group points with similar geometric information,even when such points are far from each other.We also introduce a large-scale point cloud dataset,PCNet184.It consists of 184 categories and 51,915 synthetic objects,which brings new challenges for point cloud classification,and provides a new benchmark to assess point cloud cross-domain generalization.Finally,we perform extensive experiments on point cloud classification,using ModelNet40,ScanObjectNN,and our PCNet184,and segmentation,using ShapeNetPart and S3DIS.Our method achieves comparable performance to state-of-the-art methods on these datasets,for both supervised and unsupervised learning.Code and our dataset are available at https://github.com/MingyeXu/PCNet184.