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991.
采用2-氯-2,4,4-三甲基戊烷或对二枯基氯为引发剂和TiCl4或FeCl3为共引发剂,引发异丁烯(IB)可控/活性正离子聚合与官能端基转化,设计合成不同分子量及窄分子量分布的端基官能化聚异丁烯,如双端烯丙基溴官能化聚异丁烯(Br-PIB-Br)或双端烯丙基胺官能化聚异丁烯(H2N-PIB-NH2).采用烯丙基溴/高氯酸银体系引发四氢呋喃(THF)开环聚合,合成聚四氢呋喃活性链(PTHF+).进一步通过将IB可控/活性正离子聚合与THF可控/活性正离子开环聚合2种方法相结合,设计合成2种新型官能化聚四氢呋喃-b-聚异丁烯-b-聚四氢呋喃(PTHF-b-PIB-b-PTHF)三嵌段共聚物:(1)以上述Br-PIB-Br为大分子引发剂,在AgClO4作用下引发THF活性正离子开环聚合,采用水终止活性链端,设计合成双端为羟基的HO-PTHF-b-PIB-b-PTHF-OH三嵌段共聚物(简称:FIBF-OH);(2)以上述合成的PTHF+活性链与H2NPIB-NH2链端胺基发生高效亲核取代反应,设计合成中间链段连接点含―NH―官能基团的PTHF-b-HNPIB-NH-b-PTHF三嵌段共聚物(简称:FIBF-NH).在上述三嵌段共聚物中,极性PTHF链段与非极性PIB链段的热力学不相容,导致其呈现明显的微相分离,且微观形态与共聚组成相关.PTHF均聚物易结晶,在上述共聚物中由于PTHF链段单端受限致其结晶性减弱.三嵌段共聚物分子链的中间连接点含―NH―官能基团,具有更强的氢键作用,促进PTHF链段重排并结晶,易形成更紧密的超分子网络结构,导致即使在PTHF链段相对分子量为0.7 kg·mol^-1时仍具有较强的结晶性,且结晶熔融温度明显提高.此外,由于FIBF-NH中形成超分子网络结构,使材料具有优异的自修复性能,材料表面的切痕在常温下10 min后可以完全自愈合.本文设计合成的新型官能化PTHF-b-PIB-b-PTHF三嵌段共聚物兼具有PTHF与PIB的优良性能,在生物医用、智能修复等功能材料领域具有潜在的应用前景. 相似文献
992.
Two novel lanthanum(III) silicate tellurites, namely, La4(Si5.2Ge2.8O18)(TeO3)4 and La2(Si6O13)(TeO3)2, have been synthesized by the solid state reactions and their structures determined by single crystal X-ray diffraction. The structure of La4(Si5.2Ge2.8O18)(TeO3)4 features a three-dimensional (3D) network composed of the [(Ge2.82Si5.18)O18]4− tetrahedral layers and the [La4(TeO3)4]4+ layers that alternate along the b-axis. The germanate-silicate layer consists of corner-sharing XO4 (X=Si/Ge) tetrahedra, forming four- and six-member rings. The structure of La2(Si6O13)(TeO3)2 is a 3D network composed of the [Si6O13]2− double layers and the [La2(TeO3)2]2+ layers that alternate along the a-axis. The [Si6O13]2− double layer is built by corner-sharing silicate tetrahedra, forming four-, five- and eight-member rings. The TeO32− anions in both compounds are only involved in the coordination with La3+ ions to form a lanthanum(III) tellurite layer. La4(Si5.2Ge2.8O18)(TeO3)4 is a wide band-gap semiconductor. 相似文献
993.
In this article, silicone rubber (SR)/clay nanocomposites were synthesized by a melt‐intercalation process using synthetic Fe‐montmorillonite (Fe‐MMT) and natural Na‐MMT which were modified by cetyltrimethyl ammonium bromide (CTAB). This study has been designed to determine if the presence of structural iron in the matrix can result in radical trapping and then enhance thermal stability, affect the crosslinking degree and elongation. The SR/clay nanocomposites were characterized by X‐ray diffraction (XRD) patterns and transmission electron microscopy (TEM). Exfoliated and intercalated nanocomposites were obtained. Thermo gravimetric analysis (TGA) and mechanical performance were applied to test the properties of the SR/clay nanocomposites. The presence of iron significantly increased the onset temperature of thermal degradation in SR/Fe‐MMT nanocomposites. The thermal stability, gel fraction and mechanical property of SR/Fe‐MMT were different from the SR/Na‐MMT nanocomposites. So the iron not only in thermal degradation but in the vulcanization process acted as an antioxidant and radicals trap. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
994.
An Impedimetric Aptasensor Based on a Novel Line‐Pad‐Line Electrode for the Determination of VEGF165
Ying Feng Shan Xiao Xingliang Xiong Honglei Wang Fankai Kong Yang Li Yan Zhang Longcong Chen 《Electroanalysis》2020,32(8):1843-1849
In this work, a novel, simple and label‐free line‐pad‐line electrode (LPLE) biosensor was developed for detection of vascular endothelial growth factor (VEGF165). DNA aptamer was used as a recognition element for high specificity to VEGF165, and original LPLE as the substrate electrode for high sensitivity of the biosensor. This sensor was prepared by immobilizing anti‐VEGF165 aptamers on the LPLE surface through gold‐sulfur (Au?S) bonding. Upon the addition of VEGF165, a large target‐induced conformational change in the surface‐immobilized aptamer was generated and caused variations in the interfacial properties,which led to a corresponding increase in the impedance magnitude of the LPLE. Finally, our results demonstrate that the calibration curve for VEGF165determination was linear over the range of 0.026‐31.4 fM with a detection limit as low as 0.017 fM.Additionally, our sensor was fabricated on printed circuit board (PCB) with a new electrode construction, and can potentially be implemented with the advantages of simplicity, low‐cost and easy mass production. Besides, considering its desirable sensitivity and specificity, the proposed use of LPLE provided a promising strategy for a wide variety of sensing applications. 相似文献
995.
Yu‐Jin Kong Zhi‐Ping Yan Si Li Hui‐Fang Su Kai Li You‐Xuan Zheng Shuang‐Quan Zang 《Angewandte Chemie (International ed. in English)》2020,59(13):5336-5340
A pair of propeller‐like chiral trinuclear CuI clusters ( R/S‐Cu3 ) with unique photoinduced fluorescence enhancement were prepared. R/S‐Cu3 showed intense variable luminescence after UV light irradiation, which was attributed to the stepwise oxidation of ligand in the clusters. It exhibited typical aggregation‐induced emission (AIE) (αAIE=17.3). Mechanism studies showed that metal cluster‐centered (MCC) and triplet metal‐to‐ligand charge‐transfer (3MLCT) processes are the origin of the luminescence; the processes are regulated by a restriction of intramolecular motions mechanism in a different state. The chiral structure and AIE feature endow R/S‐Cu3 with remarkable circularly polarized luminescence (glum=2×10?2) in the aggregated state. It shows good capability for producing reactive oxygen species. This work enriches the kinds of atomically precise AIE clusters, gains insight into their luminescence mechanism, and offers the prospect of application in multifunctional materials. 相似文献
996.
Desulphurization mechanism of polyethylene glycol (PEG) membranes has been investigated by the study of solubility and diffusion behavior of typical gasoline components through PEG membranes with various crosslinking degrees. The sorption, diffusion and permeation coefficients were calculated by the systematic studies of dynamic sorption curves of gasoline components such as thiophene, n-heptane, cyclohexane, cyclohexene and toluene in PEG membranes. Furthermore, the temperature dependence of diffusion and solubility coefficients and the influence of crosslinking degree on sorption and diffusion behaviors were conducted to elucidate the mass-transfer mechanism. According to the discussions on dynamic sorption curves, transport mode, activation energy and thermodynamic parameters, thiophene species were the preferential permeation components. Crosslinking is an effective modification way to improve the overall performance of PEG membranes applied in gasoline desulphurization. The pervaporation (PV) and gas chromatography (GC) experiments results corresponded to the conclusions. All these investigations will provide helpful suggestions for the newly emerged membrane desulphurization technology and complex organic mixture separation by pervaporation. 相似文献
997.
Zhenfeng Pang Hanxi Guan Lina Gao Weicheng Cao Jinglin Yin Xueqian Kong 《物理化学学报》2020,36(4):1906018-0
核磁共振(NMR)技术凭借其高空间分辨率,宽时间响应尺度和非侵入检测等特点,在化学分析和医疗诊断中发挥着重要的作用。但是原子核的低极化使现阶段NMR技术的灵敏度较低。超极化技术是一类可以有效提高NMR灵敏度的方法。其通过物理或化学过程把原子核自旋态推向一个偏离热力学平衡的状态,使NMR信号强度得到几个数量级的提升,极大地改善了灵敏度。多种超极化技术已经在各个领域崭露头角。本文用较为形象的描述对几种常见的超极化技术包括:动态核极化、光泵、光核极化、化学诱导动态核极化、仲氢诱导极化。从其精巧的原理和广泛的应用进行介绍,有助于人们对超极化技术的认知。 相似文献
998.
Previously, we described an online high-/low-pH RP-RP LC system exhibiting high-throughput, automatability, and performance comparable with that of SCX-RP. Herein, we report a variant of the RP-RP platform, RP-SCX-RP, featuring an additional SCX trap column between the two LC dimensions. The SCX column in combination with the second-dimension RP can be used as an SCX-RP biphasic column for trapping peptides in the eluent from the first RP column. We evaluated the performance of the new platform through proteomic analysis of Arabidopsis thaliana chloroplast samples and mouse embryonic mouse fibroblast STO cell lysate at low-microgram levels. In general, RP-SCX-RP enhanced protein identification by allowing the detection of a larger number of hydrophilic peptides. Furthermore, the platform was useful for the quantitative analyses of crude chloroplast samples for iTRAQ applications at low-microgram levels. In addition, it allowed the online removal of sodium dodecyl sulfate and other chemicals used in excess in iTRAQ reactions, avoiding the need for time-consuming offline SCX clean-up prior to RP-RP separation. Relative to the RP-RP system, our newly developed RP-SCX-RP platform allowed the detection of a larger number of differentially expressed proteins in a crude iTRAQ-labeled chloroplast protein sample. 相似文献
999.
1000.