Structural Evolution of UHMWPE Fibers during Poststretching with Distinct Initial Structures

By adopting a homemade extension apparatus and wide-angle X-ray diffraction(WAXD)technique,the structural evolutions of the extracted ultra-high molecular weight polyethylene(UHMWPE)fibers with different spinning draw ratios were investigated during the poststretching process.Molecular chains oriented along the axis quickly at the early stage of drawing,which is quite different from the situation of drawing with solvents.The crystal regions,which have not melted at higher temperature,show stronger rigidity in the absence of solvents.Rigid characteristics show faster response to the external field.Also,the surface morphologies of fibers after poststretching are characterized by scanning electron microscopy(SEM).The lamellae stack disordered before stretching,but arranged in order along the draw direction when the draw ratios were larger than 1.

NIR-II fluorescence imaging in liver tumor surgery: A narrative review

In liver tumor surgery,the recognition of tumor margin and radical resection of microcancer focis have always been the crucial points to reduce postoperative recurrence of tumor.However,naked-eye inspection and palpation have limited effectiveness in identifying tumor boundaries,and traditional imaging techniques cannot consistently locate tumors in real time.As an intraoperative real-time navigation imaging method,NIRfluorescence imaging has been extensively studied for its simplicity,reliable safety,and superior sensitivity,and is expected to improve the accuracy of liver tumor surgery.In recent years,the research focus of NIRfluorescence has gradually shifted from the-rst near-infrared window(NIR-I,700–900 nm)to the second near-infrared window(NIR-II,1000–1700 nm).Fluorescence imaging in NIR-II reduces the scattering effect of deep tissue,providing a preferable detection depth and spatial resolution while signi-cantly eliminating liver autofluorescence background to clarify tumor margin.Developingfluorophores combined with tumor antibodies will further improve the precision offluorescence-guided surgical navigation.With the development of a bunch offluorophores with phototherapy ability,NIR-II can integrate tumor detection and treatment to explore a new therapeutic strategy for liver cancer.Here,we review the recent progress of NIR-IIfluorescence technology in liver tumor surgery and discuss its challenges and potential development direction.

Dual-functional poly(2-methyl-2-oxazoline)/poly(2-(dimethylamine)ethyl methacrylate)mixed brushes with switchable protein adsorption and antibacterial properties

Herein,binary mixed brushes consisting of poly(2-methyl-2-oxazoline)(PMOXA)and poly(2-(dimethylamine)ethyl methacrylate)(PDMAEMA)with different chain lengths were fabricated by successive grafting of NH_(2)-terminated PMOXA and SH-terminated PDMAEMA onto polydopamine-anchored substrates.The mixed-brush coating was characterized by variable-angle spectroscopic ellipsometry,X-ray photoelectron spectroscopy,Fourier transform infrared spectroscopy,zeta potential measurements,water contact angle,and atomic force microscopy.The mixed brushes showed tunable surface charge,wettability,and surface roughness,depending on the degree of PDMAEMA swelling under varying pH and ionic strength(Ⅰ).Then the adsorption behaviors of pepsin,bovine serum albumin(BSA),γ-globulin,and lysozyme,four very different proteins with regard to isoelectric point,on the mixed brushes coating were studied by using fluorescence microscopy and surface plasmon resonance.When the chain length of PDMAEMA was about twice as long as PMOXA,the mixed brushes not only had high adsorption capacity for pepsin,BSA,and y-globulin but also had a desorption efficiency of 86.9%,87.1%,and 93.5%,respectively.It is explained that electrostatic attraction between the protonated PDMAEMA and positively charged acidic proteins(pepsin and BSA,whose isoelectric points were below the pK_(a) of PDMAEMA)would drive the intensive adsorption(at pH 3,I=10^(-3)mol·L^(-1)for pepsin,and pH 5,I=10^(-5)mol·L^(-1)for BSA),while desorption was dominated by the hydrophilic PMOXA when PDMAEMA was shrinking(at pH 7,I=10^(-1)mol·L^(-1)for pepsin,and pH 9,I=10^(-1)mol·L^(-1)for BSA).Furthermore,the isoelectric precipitation led to the adsorption of neutral protein(γ-globulin,whose isoelectric point was near the pK_a of PDMAEMA)at pH 7,I=10^(-5)mol·L^(-1),while electrostatic repulsion and antifouling PMOXA triggered the desorption of y-globulin at pH 3,I-10^(-1)mol·L^(-1).However,alkaline protein(lysozyme,whose isoelectric point was higher than the pK_(a) of PDMAEMA)exhibited slight adsorption on PMOXA/PDMAEMA mixed brushes under test conditions,regardless of whether PMOXA or PDMAEMA occupied the outermost layer.The antibacterial property of the mixed brushes against Escherichia coli was investigated.PMOXA/PDMAEMA mixed brushes showed significant bactericidal activity at pH 3,I=10^(-3)mol·L^(-1),while the rinse of pH 9,I=10^(-1)mol·L^(-1)solution could remove most of the residual bacteria.This work not only enables controlled adsorption of proteins with different isoelectric points but also ensures that the surface of the coating is minimized from bacterial contamination.

Rheo-NMR: A versatile hyphenated technique for capturing molecular dynamics and structure under flow

The general development of Rheo-NMR during the last four decades as well as selective hyphenated apparatuses is presented.Based on different magnet types,the current review is divided into two categories,namely low-field and high-field NMR,while the timedomain NMR is normally applied in the former case and the frequency-domain NMR is adopted in the latter one.Depending on different rheometer cells,it can be further divided into tensile and shear mode Rheo-NMR.The combination of various rheometer cells and NMR facility guarantees our acquisition of molecular level structure and dynamics information under flow conditions,which is crucial for our understanding of the molecular origin of complex fluids.A personal perspective is also presented at last to highlight possible development in this direction.

One-pot degradation of cellulose into carbon dots and organic acids in its homogeneous aqueous solution

As the abundant biopolymer, cellulose can be used as a feedstock for chemicals and materials. Effective conversion of cellulose by simple processes is a key point. Degradation of cellulose in its homogeneous solution is attractive for the molecular chains are free and spread. Here,microcrystalline cellulose was first dissolved in aqueous solution of Na OH and urea, and then hydrothermal reaction was carried out at various temperature and time. Fluorescence carbon dots(CDs) were generated accompanied with six organic acids: oxalic acid, formic acid, malonic acid, lactic acid, acetic acid, and fumaric acid. The yields of all organic acids and CDs, and the fluorescence quantum yield(QY) of CDs were studied at different reaction conditions. It was found that the maximum yield of organic acids and CDs are 80.1% and 6.03%, respectively, and the highest QY of the CDs is 10.9%. Fluorescence studies reveal that the as-prepared CDs has efficient selectivity and sensitivity toward iron ions in acidic condition, indicating it is a potential fluorescent sensor to the detection of Fe3+. Importantly, it provides a panorama to summary the degradation routes of cellulose in its homogeneous aqueous solution with both organic molecules and CDs as products.

Engineering Leaf-Like UiO-66-SO3H Membranes for Selective Transport of Cations

Metal–organic frameworks(MOFs)with angstrom-sized pores are promising functional nanomaterials for the fabrication of cation permselective membranes(MOF-CPMs).However,only a few research reports show successful preparation of the MOF-CPMs with good cation separation performance due to several inherent problems in MOFs,such as arduous selfassembly,poor water resistance,and tedious fabrication strategies.Besides,low cation permeation flux due to the absence of the cation permeation assisting functionalities in MOFs is another big issue,which limits their widespread use in membrane technology.Therefore,it is necessary to fabricate functional MOF-CPMs using simplistic strategies to improve cation permeation.In this context,we report a facile in situ smart growth strategy to successfully produce ultrathin(<600 nm)and leaflike UiO-66-SO3H membranes at the surface of anodic alumina oxide.The physicochemical characterizations confirm that sulfonated angstrom-sized ion transport channels exist in the as-prepared UiO-66-SO3H membranes,which accelerate the cation permeation(~3×faster than non-functionalized UiO-66 membrane)and achieve a high ion selectivity(Na^+/Mg^2+>140).The outstanding cation separation performance validates the importance of introducing sulfonic acid groups in MOF-CPMs.

Preparation and Conducting Behavior of Amphibious Organic/Inorganic Hybrid Proton Exchange Membranes Based on Benzyltetrazole

A series of novel amphibious organic/inorganic hybrid proton exchange membranes with H3PO4 doped which could be used under both wet and dry conditions was prepared through a sol-gel process based on acrylated triethoxysilane（A-TES） and benzyltetrazole-modified triethoxysilane（BT-TES）.The dual-curing approach including UV-curing and thermal curing was used to obtain the crosslinked membranes.Polyethylene glycol（400） diacrylate（PEGDA） was used as an oligomer to form the polymeric matrix.The molecular structures of precursors were characterized by 1 H,13 C and 29 Si NMR spectra.The thermogravimetric analysis（TGA） results show that the membranes exhibit acceptable thermal stability for their application at above 200 oC.The differential scanning calorimeter（DSC） determination indicates that the crosslinked membranes with the mass ratios of below 1.6 of BT-TES to A-TES and the same mass of H3PO4 doped as that of A-TES possess the-T g s,and the lowest T g（-28.9 ℃） exists for the membrane with double mass of H3PO4 doped as well.The high proton conductivity in a range of 9.4―17.3 mS/cm with the corresponding water uptake of 19.1%―32.8% of the membranes was detected at 90 oC under wet conditions.Meanwhile,the proton conductivity in a dry environment for the membrane with a mass ratio of 2.4 of BT-TES to A-TES and double H3PO4 loading increases from 4.89×10-2 mS/cm at 30 ℃ to 25.7 mS/cm at 140 ℃.The excellent proton transport ability under both hydrous and anhydrous conditions demonstrates a potential application in the polymer electrolyte membrane fuel cells.

Effects of Soluble Ions on Hydration of Calcined Flue Gas Desulphurization Gypsum

The influence of various water soluble cations(K^+,Na^+,Ca^2+,Mg^2+)on the hydration of calcined flue gas desulphurization gypsum was investigated.The results show that all cations but Ca^2+can accelerate the hydration of bassanite.The final crystal size is not largely influenced by different salts,except for Na^+,where the giant crystal with length of>130μm is observed.Current study clarifies the influence of different ions on the hydration of bassanite,which could provide sufficient guide for the pre-treatment of original flue gas desulphurization gypsum before actual application.

Photoinitiating Characteristics of Benzophenone Derivatives as Type II Macromolecular Photoinitiators Used for UV Curable Resins

Dodecyl-benzophenone（DBP） and hexadecoxyl-benzophenone（HDBP） as type 11 photoinitiators used for radical photopolymerization systems were synthesized by Friedel-Crafts reaction, and characterized by 1H NMR and FTIR spectroscopy. The UV-Vis absorption spectra of DBP and HDBP, propitious to photopolymerization under a commercial mercury UV bulb are centered at 345 and 335 nm, respectively. HDBP has higher extinction coefficient than DBP, but lower photoinitiating efficiency. Their photoinitiating performances for EB605, a bisphenol A epoxy acrylate with 40%（mass fraction） tripropyleneglycol diacrylate （TPGDA）, resin consisting of bisphenol A epoxy acrylate and tripropyleneglycol diacrylate in the presence of triethanolamine as a coinitiator were investigated by photo-differential scanning calorimetry（photo-DSC）. DBP initiates the curing of acrylate more efficiently than HDBP, showing higher photopolymerization rate and unsaturation conversion, resulted from the poor compatibility of HDBP with the resin. The photoinitiating activity of DBP to epoxy acrylate resin is even higher than that of BP at lower loadings.

Synthesis and characterization of fluorinated PEO-b-PDMS-b-fluorinated PEO by free radical addition

Fluorinated poly（ethylene oxide） propyl-b-polydimethylsiloxane-b-propyl fluorinated poly（ethylene oxide） （FPEO-b-PDMS-b- FPEO） was synthesized by a free radical addition of carbon-hydrogen of polyether segments of poly（ethylene oxide） propyl-b- polydimethylsiloxane-b-propyl poty（ethylene oxide） （PEO-b-PDMS-b-PEO） to hexafluoropropylene （HFP） using tert-butyl peroxypivalate as an initiator. In order to reduce the possibility of side reaction, the protection and deprotection via silylation were used for the end-hydroxyls in PEO-b-PDMS-b-PEO chain. The structure of Intermediates and FPEO-b-PDMS-b-FPEO was confirmed by means of Fourier transform infrared and 1H NMR spectroscopy. The effects of amount of initiator, reaction temperature and time on free radical addition were investigated in detail. 2009 Xing Yuan Zhang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Fabrication of Monodisperse ＂Core-Satellite＂ Nanostructures by DNA-Programming： a Novel Class of Superstructured Building Blocks for Hierarchical Nanoassembly

Monodisperse nanoparticle assembly with tunable structure, composition and properties can be taken as a superstructured building block for the construction of hierarchical nanostruc tures from the bottom up, which also represents a great challenge in nanotechnology. Here we report on a facile and controllable method that enables a high yield fabricatioa of uniform gold nanoparticle （AuNP） coresatellites with definable number （in average） of the satellite particles and tunable coretosatellite distance. The formation of the coresatellite nanostruc tures is driven by programmable DNAbasepairing, with the resulting nanocomplexes being isolatable via gel electrophoresis. By rationally controlling the DNA coverages on the core and shell particles, high production yields are achieved for the assembly/isolation process. As well, benefiting from a minimum DNA coverage on the satellite AuNPs, a strong affinity is observed for the asprepared coresatellites to get adsorbed on proteincoated graphene ox ide, which allows for a twodimensional hierarchical assembly of the coresatellite structures. The resulting hierarchical nanoassemblies are expected to find applications in various areas, including plasmonics, biosensing, and nanocatalysis. The method should be generalizable to make even more complicated and higherorder structures by making use of the structural programmability of DNA molecules.

Synthesis and characterization of a novel hydroxypolyether blocked polydimethylsiloxane PEO-b-PDMS-b-PEO

A novel hydroxypolyether blocked polydimethylsiloxane, poly（ethylene oxide） propyl-b-polydimethylsiloxane-b-propyl poly（ethylene oxide） （PEO-b-PDMS-b-PEO） was synthesized by simple hydrosilation reaction of poly（ethylene glycol） monoallyl ether with α,ω-dihydrogen terminated PDMS （HPDMS）. Fourier transform infrared spectroscopy （FTIR） and IH NMR were used to identify the structure of PEO-b-PDMS-b-PEO and intermediate product HPDMS. Based on the effect investigations of temperature, reactant molar ratio, catalyst and time on the hydrosilation, it was found that the conversion of Si-H bond to SiC bond increased with the increase of catalyst and time, and the reaction completed when the content of catalyst was 22μg/g and the time was 5 h, respectively. Urethane reaction of OH and NCO group confirms that PEO-b-PDMS-b-PEO is more reactive toward to diisocyanate than α,ω-dihydroxylbutyl terminated PDMS.

Superabsorbent Capability and High Retention Ability of China Clay(Kaolinite)/Polyacrylic Acid Composites for Aqueous Solution

Majority of superabsorbent polymers (SAPs) yet reported either have low gel strength or high production cost. Therefore, we synthesized a novel polyacrylic acid-grafted China clay (Kaolinite) super-absorbent polymer composite (SAPC) with high thermal stability, low cost of production and superior sorption and retention capability for water and salt solution. The resulting SAPCs were extensively characterized and analysed by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Results suggested that the composites were thermally stable. Water absorbency increased with increase of clay content up to 45%, while further increase in clay content decreased the water absorbency. Percentage of acrylic acid (AA) and clay by weight shows the optimum absorbency in 35% and 40% respectively. Crosslinker and initiator contents were optimized to be 0.5% and 0.3% by weight respectively. The resulting polymer composite showed high water absorbency of about 785 g/g and 103 g/g of 1% NaCl solution with above 90% retention ability at 50 oC.

Jamming of packings of frictionless particles with and without shear

By minimizing the enthalpy of packings of frictionless particles, we obtain jammed solids at desired pressures and hence investigate the jamming transition with and without shear. Typical scaling relations of the jamming transition are recovered in both cases. In contrast to systems without shear, shear-driven jamming transition occurs at a higher packing fraction and the jammed solids are more rigid with an anisotropic force network. Furthermore, by introducing the macrofriction coefficient, we propose an explanation of the packing fraction gap between sheared and non-sheared systems at fixed pressure.

Polyaniline Nanotubes Prepared by One-Step Synergistic Polymerization of Aniline and Acrylic Acid

The electrochemical property of electrode materials greatly depends on their morphologies. This report introduces a novel and facile synthesis method for polyaniline (PANI) nanotubes from one-step synergistic polymerization of aniline and acrylic acid in an aqueous solution induced by the addition of ammonium persulfate (APS). The molar ratio of aniline to AA (X{ani/AA}) is found to have great in fluence on the morphology of the produced PANI. Hollow PANI nanotubes with an average inner diameter of 80 nm and outer diameter of 180 nm can be mainly produced when X{ani/AA} is not higher than 1. The electrochemical properties of the prepared PANI nanotubes have been investigated using a three-electrode system. The specific capacitance of PANI nanotubes can reach 436 F/g at a current density of 0.5 A/g in 1 mol/L H2SO4 solution. Furthermore, the specific capacitance of the PANI nanotube maintains 89.2% after 500 charging/discharging cycles at a current density of 0.5 A/g, indicating a good cycling stability.

Photo-induced Alignment Behavior of Azobenzene-containing Polymer Films with Different Cross-linking Degree

Three series of amorphous copolymers containing azobenzene groups with various substituents and certain amounts of crosslinkable acrylic groups were prepared. The cross-linked polymer films were obtained by thermal polymerization of the acrylic groups in the copolymers, during which, by controlling the time of cross-linking reaction, the films can be made with different cross-linking degree （from 0 to 32%, which was monitored by FT-IR spectra measurement）. Photo-induced alignment process of the films was performed under irradiation with linearly polarized light at 442 nm, and the effect of cross-linking degree on the photo-induced alignment rate was investigated. The dynamics of the photo-induced alignment was analyzed with biexponential curve fitting. The photo-induced alignment rate and the maximum transmittance of the films decreased because of the cross-linking. Furthermore, for the cross-linked samples, it was found that their saturated value of transmittances keep constant after repeated ＂writing＂ and ＂erasing＂ cycles. The findings reveal that the cross-linking of the film can effectively restrain the phototactic mass transport of azopolymer during irradiation by polarized light. The relationship between the cross-linking degree and the photo-induced alignment behavior of azopolymer is discussed in detail.

Near-Field Scattering Enhancement of Perylene Based Aggregates for Random Lasing

Strong near-field scattering enhancement (NFSE) of polyhedral oligomeric silsesquioxanes(POSS) nanoparticles (NPs) aggregates is found through physical simulation. An aggregation of N,N′-di-[3-(isobutyl polyhedral oligomeric silsesquioxanes) propyl] perylene diimide(DPP) which possesses POSS as scatteres experimentally performs strong NFSE, which confirms the physical simulation results. Moreover, coherent random laser is triggered from the DPP aggregates in carbon disulfide. It is the NFSE of POSS NPs connected to both ends of DPP through covalent bonds and the NFSE of their aggregation thanks to DPP’s aggregation that is responsible for the coherent random laser. So, this work develops a method to improve weak scattering of system through construction of molecules, and opens a road to a variety of novel interdisciplinary investigations, involving molecular designing for disordered photonics.

Location Effect in a Photocatalytic Hybrid System of Metal-Organic Framework Interfaced with Semiconductor Nanoparticles

We report an ultrafast spectroscopy investigation that addresses the subtle location effect in a prototypical semiconductor-MOF hybrid system with TiO2 nanoparticles being incorporated inside or supported onto Cu3(BTC)2,denoted as TiO2@Cu3(BTC)2 and TiO2/Cu3(BTC)2,respectively.By tracking in real time the interface electron dynamics in the hybrid system,we find that the interface states formed between TiO2 and Cu3(BTC)2 can act as an effective relay for electron transfer,whose effciency rests on the relative location of the two components.It is such a subtle location effect that brings on difference in photocatalytic CO2 reduction using the two semiconductor-MOF hybrids.The mechanistic understanding of the involved interface electron-transfer behavior and effect opens a helpful perspective for rational design of MOF-based hybrid systems for photoelectrochemical applications.

Impact of Zn(Ⅱ)Ions on Crystallization and Thermal Properties of Poly(lactic acid)

The issues of low crystallinity and slow crystallization rate of poly(lactic acid)(PLA)have been widely addressed.In this work,we find that doping PLA with Zn(Ⅱ)ions can speed up the process of crystallization of PLA.Three kinds of Zn(Ⅱ)salts(ZnCl2,ZnSt and ZnOAc)were tested in comparison with some other ions such as Mg(Ⅱ)and Ca(Ⅱ).The increased crystallinity and crystallization rate of PLA doping with Zn(Ⅱ)are reflected in FT-IR and variable temperature Raman spectroscopy.The crystallinity is further confirmed or measured with differential scanning calorimetry and X-ray diffraction.The crystallinity rate of the PLA/ZnSt-0.4 wt%material can reach 22.46% and the crystallinity rate of the PLA/ZnOAc-0.4 wt%material can reach 24.83%,as measured with differential scanning calorimetry.

Mechanical properties of jammed packings of frictionless spheres under an applied shear stress

By minimizing a thermodynamic-like potential, we unbiasedly sample the potential energy landscape of soft and frictionless spheres under a constant shear stress. We obtain zero-temperature jammed states under desired shear stresses and investigate their mechanical properties as a function of the shear stress. As a comparison, we also obtain the jammed states from the quasistatic-shear sampling in which the shear stress is not well-controlled. Although the yield stresses determined by both samplings show the same power-law scaling with the compression from the jamming transition point J at zero temperature and shear stress, for finite size systems the quasistatic-shear sampling leads to a lower yield stress and a higher critical volume fraction at point J. The shear modulus of the jammed solids decreases with increasing shear stress. However, the shear modulus does not decay to zero at yielding. This discontinuous change of the shear modulus implies the discontinuous nature of the unjamming transition under nonzero shear stress, which is further verified by the observation of a discontinuous jump in the pressure from the jammed solids to the shear flows. The pressure jump decreases upon decompression and approaches zero at the critical-like point J, in analogy with the well-known phase transitions under an external field. The analysis of the force networks in the jammed solids reveals that the force distribution is more sensitive to the increase of the shear stress near point J. The force network anisotropy increases with increasing shear stress. The weak particle contacts near the average force and under large shear stresses it exhibit an asymmetric angle distribution.