Hierarchical Tubular Structures Grown from the Gel/Liquid Interface

Three dimensional hierarchical materials are widespread in nature but are difficult to synthesize by using self‐assembly/organization. Here, we employ a gel–liquid interface to obtain centimeter‐long ～100 μm diameter tubes with complex mineral wall structures that grow from the interface into solution. The gel, made from gelatin, is loaded with metal chloride salt, whereas the solution is a high pH anion source. Tubes were obtained with a range of cations (Ca²⁺, Sr²⁺, Ba²⁺, Cu²⁺, and Zn²⁺) and anions (CO₃^2? and PO₄^3?). The crystalline phases found in the tube walls corresponded to expectations from solution chemistries and phase solubilities. The growth mechanism is found to be akin to that of chemical gardens. The divalent cations modify the strength of the gelatin gel in a manner that involves not only simple electrostatic screening, but also ion‐specific effects. Thus, tubes were not obtained for those ions and/or concentrations that significantly changed the gel’s mechanical structure. At high Cu²⁺ loading, for example, vertical convection bands, not Liesegang bands, were observed in the gels.     

基于微流控技术的蛋白质结晶及其筛选方法的研究进展简

微流控技术以其高通量、低消耗和集成化等优点成为蛋白质结晶微型化研究的重要手段. 本文综述了基于微流控技术的蛋白质结晶技术和方法,主要包括微泵微阀、液滴(Droplet)、滑动芯片(SlipChip)以及液滴实验室(DropLab)等技术. 此外,还针对当前膜蛋白在结构生物学研究中的重要地位,综述了应用于膜蛋白结晶的微流控技术的研究进展.     

晶化时间对ZSM-5/MCM-48复合分子筛结构及MTG反应性能的影响

采用两步晶化法制备ZSM-5/MCM-48微介孔复合分子筛,通过调变前驱体溶胶的晶化时间获得不同结构的ZSM-5/MCM-48基分子筛催化剂。采用XRD、N₂-吸附、SEM、TEM、FT-IR和Py-FTIR等手段进行表征,结果表明,前驱体溶胶的晶化时间对ZSM-5/MCM-48复合分子筛的结构和表面酸性产生重要的影响,而特定结构的复合分子筛基催化剂可以显著改变甲醇制汽油（MTG）反应的产物分布,与ZSM-5基催化剂相比显著降低了油品中芳烃和均四甲苯的含量。阐明了其催化作用机制是由于介孔结构的MCM-48对微孔结构的ZSM-5界面或表面的修饰作用。     

树枝状嵌段聚合物D-PCL-b-PS在不对称末端受限条件下的结晶行为

研究了树枝状嵌段聚合物聚(ε-b-己内酯)-b-聚苯乙烯(D-PCL-b-PS)的分子结构对PCL链段受限结晶行为的影响.首先,通过活性正离子开环聚合(ROP)合成了树枝状的嵌段聚合物D-PCL.在此基础上用原子转移自由基聚合(ATRP)的方法,合成了树枝状的嵌段聚合物D-PCL-b-PS,在结晶的PCL链段的两个末端...     

溶胶-凝胶-水热晶化法制备锐钛矿TiO2纳米膜的耐蚀性能

以钛酸正丁酯为前驱体, 采用溶胶-凝胶-水热晶化法在不锈钢(SS)表面制备TiO₂纳米膜. 利用X射线衍射(XRD)、Raman光谱、场发射扫描电子显微镜(SEM)、原子力显微镜(AFM)和俄歇电子能谱(AES)表征了TiO₂纳米膜的晶型、表面形貌和表面化学组成. 通过极化曲线和电化学阻抗谱(EIS)研究了TiO₂纳米膜的耐蚀性能. 170 °C下水热晶化制备的锐钛矿TiO₂与450 °C焙烧制备的锐钛矿TiO₂的结晶度类似, 但两种TiO₂薄膜的表面结构存在明显差异, 水热晶化法制备的TiO₂纳米膜在3.5% (w) NaCl溶液中的耐蚀性能优于焙烧法制备的.     

Super-nucleation in nanocomposites and confinement effects on the crystallizable components within block copolymers, miktoarm star copolymers and nanocomposites

In this paper we reexamine recent results obtained by our group on the crystallization of nanocomposites and linear and miktoarm star copolymers in order to obtain some general features of their crystallization properties. Different nanocomposites have been prepared where a close interaction between the polymer matrix and the nano-filler has been achieved: in situ polymerized high density polyethylene (HDPE) on carbon nanotubes (CNT); and polycaprolactone (PCL) and poly(ethylene oxide) (PEO) covalently bonded to carbon nanotubes. In all these nanocomposites a “super-nucleation” effect was detected where the CNTs perform a more efficient nucleating action than the self-nuclei of the polymer matrix. It is believed that such a super-nucleation effect stems from the fact that the polymer chains are tethered to the surface of the CNT and can easily form nuclei. For polystyrene (PS) and PCL block copolymers, miktoarm star copolymers (with two arms of PS and two arms of PCL) were found to display more compact morphologies for equivalent compositions than linear PS-b-PCL diblock copolymers. As a consequence, the crystallization of the PCL component always experienced much higher confinement in the miktoarm stars case than in the linear diblock copolymer case. The consequences of the topological confinement of the chains in block copolymers and nanocomposites on the crystallization were the same even though the origin of the effect is different in each case. For nanocomposites a competition between super-nucleation and confinement was detected and the behavior was dominated by one or the other depending on the nano-filler content. At low contents the super-nucleation effect dominates. In both cases, the confinement increases as the nano-filler content increases or the second block content increases (in this case a non-crystallizable block such as PS). The consequences of confinement are: a reduction of both crystallization and melting temperatures, a strong reduction of the crystallinity degree, an increase in the supercooling needed for isothermal crystallization, a depression of the overall crystallization rate and a decrease in the Avrami index until values of one or lower are achieved indicating a nucleation control on the overall crystallization kinetics.     

Microphase separation in polybenzoxazine thermosets containing benzoxazine-terminated poly(ethylene oxide) telechelics

Benzoxazine-terminated poly(ethylene oxide) telechelics (Ba-terminated PEO) was synthesized and incorporated into polybenzoxazine to obtain the nanostructured thermosets. The morphology of the thermosets was investigated by means of atomic force microscopy (AFM), small angle X-ray scattering (SAXS) and dynamic mechanical analysis (DMA). The formation of the nanophase structures in the thermosetting composites was addressed on the basis of the mechanism of reaction-induced microphase separation (RIMPS), which was in marked contrast to the case of the binary thermosetting blends of polybenzoxazine with hydroxyl-terminated poly(ethylene oxide). The occurrence of RIMPS resulted from the copolymerization reaction of the end groups of Ba-terminated PEO telechelics with the precursor of thermosetting matrix (i.e., benzoxazine), which suppressed the occurrence of the macroscopic phase separation. It was found that the formation of the nanostructures has a significant effect on the melting behavior of PEO in the thermosets, thermal transition properties of the PBZ thermosets.     

两步晶化法合成纳米SAPO-34分子筛及其催化性能

分别以拟薄水铝石、硅溶胶和磷酸为铝源、硅源和磷源,四乙基氢氧化铵为模板剂,采用两步水热晶化法合成出粒径为200～300 nm的纳米级SAPO-34分子筛.采用X射线衍射(XRD)、X射线荧光光谱(XRF)、29Si 、27Al、31P MAS NMR、SEM、BET和NH3-TPD等手段对合成的SAPO-34分子筛进行...     

尼龙6/蒙脱土纳米复合材料非等温结晶动力学和透明性研究

将有机化的蒙脱土与尼龙6(PA6)在Haake共混机中共混,制备出尼龙6/蒙脱土纳米复合材料(PA6N);对尼龙6/蒙脱土纳米复合材料和纯尼龙6分别进行差示扫描量热法非等温结晶试验,以了解蒙脱土在尼龙6/蒙脱土纳米复合材料中的成核作用、扩大尼龙6在包装领域的应用范围.与此同时,采用偏光显微镜测定了样品的结晶形态;采用紫...     

Biodegradable poly(p‐dioxanone) reinforced and toughened by organo‐modified vermiculite

Poly(p‐dioxanone) (PPDO)/vermiculite (VMT) nanocomposites with exfoliated structure were prepared successfully by in situ intercalative polymerization of p‐dioxanone (PDO) in the presence of organo‐modified vermiculite (OVMT) with the aid of ultrasonic action. The nano‐structure of the nanocomposites was established using X‐ray diffraction (XRD) analysis and transmission electron microscopy (TEM) observations. The investigation of crystallization behavior by differential scanning calorimetry (DSC) and polarized optical microscopy (POM) proved that exfoliated OVMT platelets acted as a template for spherulite growth. The thermal stability of nanocomposites was enhanced than that of pure PPDO. Dynamic mechanical analysis (DMA) indicated nanoscale OVMT platelets restricted the motion of PPDO segments, which benefitted the increase of storage and loss modulus. The tensile properties showed that nanocomposites were reinforced and toughened significantly by the addition of nanoscale OVMT platelets. Copyright © 2009 John Wiley & Sons, Ltd.