Stereocomplex poly(lactic acid) vascular stents by 3D‐printing with long chain branching structures: Toward desirable crystallization properties and mechanical performance

Using pyromelliticdianhydride (PMDA) and polyfunctional epoxy ether (PFE) as branching agent, long chain branching stereocomplex poly(L‐lactide)s and poly(D‐lactide)s was prepared by reactive processing, respectably. Then stereocomplex poly(lactide)s of long chain branching PLLA and PDLA (sc‐PLA/BA) was prepared by solution blending and its fabricated the vascular stents via 3D‐printing.The effects of branching structure on melt crystallization behavior of sc‐PLA/BA investigated by DSC. The influence of the branching agent content on the crystallization ability of samples shows a bell‐shaped relationship, there is a maximum point when the branching agent content is1.5 wt%. When the branching agent content is less than 1.5 wt%, the crystallization ability of the sample increased with the increasing of branching agent content. When the branching agent content exceeded than 1.5 wt%, the crystallization ability of the samples decreased with branching agent content increasing. Such behavior is as the linear PLA branched to dendrite configuration, the enrichment of segments around branching structure within branched chains promoted its nucleation. But the high degree of branching caused inter‐ or intrachians entanglement which obstructed the segments movement and growth into the crystals. The half‐time of crystallization (t_1/2) of the samples decreased from 6 minutes for initial sc‐PLA/BA‐0 to 3 minutes of sc‐PLA/BA‐1.5 wt% at 163°C. POM results indicated that nucleation density of sc‐PLA/BA significantly increased with the branching agent increasing. Moreover, mechanical testing demonstrated that forming branching structure could be an effective modification of the mechanical properties for sc‐PLA, its tensile strength and modulus increases from 57.3 MPa and 2.02 GPa to 70.4 MPa and 3.31 GPa, respectively. TGA results analyzed by FWO method and Kissinger method, indicated the apparent activation energy of sc‐PLA/BA samples increases from 96.8 to 113.3 kJ/mol, suggesting the improvement of heat resistance. The CCK‐8 assay, ALP assay and cell Live/Dead assay results indicated that sc‐PLA with branching structure presented very low cell cytotoxicity. Therefore, the long chain branching sc‐PLA matrix with branching agent could effectively improve its crystallization abilities, mechanical properties, heat resistance and biocompatibilities.     

Recent progress on polymer-based fluorescent and colorimetric chemosensors

Recently, fluorescent or colorimetric chemosensors based on polymers have attracted great attention due to several important advantages, such as their simplicity of use, signal amplification, easy fabrication into devices, and combination of different outputs, etc. This tutorial review will cover polymer-based optical chemosensors from 2007 to 2010.     

THE FRACTAL RESEARCH AND PREDICATING ON THE TIME SERIES OF SUNSPOT RELATIVE NUMBER

IntroductionThesunspotnumberisanindexwhichnsummarizestheactivitiesofthesun.IthasbeenusedsinceWolfadvanceditin1949.Inreality,yet,onlyitsmonthlymeanvariation,monthlyslipvariationandannuallymeanvariationarevaluable.Intheearlyworksofresearch,Peopletriedtodescribethelawofitsprocessbysomekindsofmodeling,whichturnedouttobeofgreatdifficultybecauseofthechaoticvaluesofthosesuchasthemonthlymeanvariationofthesunspotnumber.Thisfactindicatedthattheprocessofthesunspotnumberishighlycomplicated.Withthedevelo…     

用正电子谱学研究USY沸石中二次孔的脱水

超稳Ｙ型沸石（ＵＳＹ）分子筛是石油催化裂化中的优异催化剂,它是由ＨＹ型沸石经高温水热处理制备的,它的特点之一是具有良好的热稳定性．因而,对ＵＳＹ的改性研究一直受到关注［１-５］,尤其是在制备ＵＳＹ过程中由于水热处理所产生大量二次孔,它与ＵＳＹ的结构与?..     

Optimised Method for Short-Chain Fatty Acid Profiling of Bovine Milk and Serum

Short-chain fatty acids (SCFA, C2-C5) in milk and serum are derived from rumen bacterial fermentation and, thus, have the potential to be used as biomarkers for the health status of dairy cows. Currently, there is no comprehensive and validated method that can be used to analyse all SCFAs in both bovine serum and milk. This paper reports an optimised protocol, combining 3-nitrophenylhydrazine (3-NPH) derivatisation and liquid chromatography-mass spectrometry (LC-MS) analysis for quantification of SCFA and β-hydroxybutyric acid (BHBA) in both bovine milk and bovine serum. This method is sensitive (limit of detection (LOD) ≤ 0.1 µmol/L of bovine milk and serum), accurate (recovery 84–115% for most analytes) and reproducible (relative standard deviation (RSD) for repeated analyses below 7% for most measurements) with a short sample preparation step. The application of this method to samples collected from a small cohort of animals allowed us to reveal a large variation in SCFA concentration between serum and milk and across different animals as well as the strong correlation of some SCFAs between milk and serum samples.     

High‐Performance Quinoline‐Malononitrile Core as a Building Block for the Diversity‐Oriented Synthesis of AIEgens

In vivo fluorescent monitoring of physiological processes with high‐fidelity is essential in disease diagnosis and biological research, but faces extreme challenges due to aggregation‐caused quenching (ACQ) and short‐wavelength fluorescence. The development of high‐performance and long‐wavelength aggregation‐induced emission (AIE) fluorophores is in high demand for precise optical bioimaging. The chromophore quinoline‐malononitrile (QM) has recently emerged as a new class of AIE building block that possesses several notable features, such as red to near‐infrared (NIR) emission, high brightness, marked photostability, and good biocompatibility. In this minireview, we summarize some recent advances of our established AIE building block of QM, focusing on the AIE mechanism, regulation of emission wavelength and morphology, the facile scale‐up and fast preparation for AIE nanoparticles, as well as potential biomedical imaging applications.     

The influence of driving force on intramolecular electron transfer: A theoretical study of subphthalocyanine-AzaBODIPY-C60 supramolecular triad

The driving force of electron transfer is one of important factors for initializing inter- and intramolecular charge separation. In this work, the main goal is to understand how driving force determines electron transfer pathway in subphthalocyanine-AzaBODIPY-C₆₀ supramolecular triad. Experimental observations have suggested that there are only two intramolecular charge transfer states (subPC⁺-AzaBODIPY⁻-C₆₀ and subPC⁺-AzaBODIPY-C₆₀⁻) after photon absorption, where subPC is the donor. Through the calculations by using tuned long range corrected density functionals with polarizable continuum model, we find two more new intramolecular charge transfer states: subPC⁻-AzaBODIPY⁺-C₆₀ and subPC-AzaBODIPY⁺-C₆₀⁻, where AzaBODIPY is the donor. We compare the HOMO/LUMO energy of subPC, AzaBODIPY, and C₆₀ monomers to their corresponding orbital energy in the triad. The results indicate that the driving force (HOMO/LUMO energy offsets) is not enough for electron transfer from AzaBODIPY to subPC or C₆₀, which can explain why subPC⁻-AzaBODIPY⁺-C₆₀ and subPC-AzaBODIPY⁺-C₆₀⁻ intramolecular charge transfer states cannot be observed in the experiment. In addition, this work may provide a simple and practical method to find the intramolecular charge transport pathway of a supramolecule.     

High-Performance Quinoline-Malononitrile Core as a Building Block for the Diversity-Oriented Synthesis of AIEgens

In vivo fluorescent monitoring of physiological processes with high-fidelity is essential in disease diagnosis and biological research, but faces extreme challenges due to aggregation-caused quenching (ACQ) and short-wavelength fluorescence. The development of high-performance and long-wavelength aggregation-induced emission (AIE) fluorophores is in high demand for precise optical bioimaging. The chromophore quinoline-malononitrile (QM) has recently emerged as a new class of AIE building block that possesses several notable features, such as red to near-infrared (NIR) emission, high brightness, marked photostability, and good biocompatibility. In this minireview, we summarize some recent advances of our established AIE building block of QM, focusing on the AIE mechanism, regulation of emission wavelength and morphology, the facile scale-up and fast preparation for AIE nanoparticles, as well as potential biomedical imaging applications.     

Formation of a large‐scale shish‐kebab structure of polyoxymethylene in the melt spinning and the crystalline morphology evolution after hot stretching

Polyoxymethylene (POM) fiber was produced by melt spinning with a high take‐up speed, which imposed a strong flow field. An unexpected formation of a shish‐kebab morphology with multiple shish of POM fibers was reported for the first time. This morphology is a large‐scale shish kebab with a diameter of 10.5 µm. Further orientation of the POM fiber was obtained by hot stretching twice at 160°C. Two crystalline morphology evolution processes were also observed: (i) the process from the large‐scale shish‐kebab to the deformed small shish‐kebab and (ii) the process from the deformed small shish‐kebab to the perfect whiskers. Compared with the melt spinning fiber, fiber tensile strength with first and second hot stretching increased by 976% and 1705%, respectively. The crystalline melting behavior of fibers significantly changes after the first and second hot stretching. The flow field induces a large number of extended chain crystals. Copyright © 2014 John Wiley & Sons, Ltd.     

Nano Carbon Doped Polyacrylamide Gel Electrolytes for High Performance Supercapacitors

Novel polyacrylamide gel electrolytes (PGEs) doped with nano carbons with enhanced electrochemical, thermal, and mechanical properties are presented. Carboxylated carbon nanotubes (fCNTs), graphene oxide sheets (GO), and the hybrid of fCNT/GO were embedded in the PGEs to serve as supercapacitor (SC) electrolytes. Thermal stability of the unmodified PGE increased with the addition of the nano carbons which led to lower capacitance degradation and longer cycling life of the SCs. The fCNT/GO-PGE showed the best thermal stability, which was 50% higher than original PGE. Viscoelastic properties of PGEs were also improved with the incorporation of GO and fCNT/GO. Oxygen-containing functional groups in GO and fCNT/GO hydrogen bonded with the polymer chains and improved the elasticity of PGEs. The fCNT-PGE demonstrated a slightly lower viscous strain uninform distribution of CNTs in the polymer matrix and the defects formed within. Furthermore, ion diffusion between GO layers was enhanced in fCNT/GO-PGE because fCNT decreased the aggregation of GO sheets and improved the ion channels, increasing the gel ionic conductivity from 41 to 132 mS cm⁻¹. Finally, MnO₂-based supercapacitors using PGE, fCNT-PGE, GO-PGE, and fCNT/GO-PGE electrolytes were fabricated with the electrode-specific capacitance measured to be 39.5, 65.5, 77.6, and 83.3 F·g⁻¹, respectively. This research demonstrates the effectiveness of nano carbons as dopants in polymer gel electrolytes for property enhancements.