多检测GPC/SEC技术在高分子表征中的应用Ⅳ.氘化高分子的溶液性质

采用体积排斥色谱法／ 示差折光指数／ 直角激光光散射／ 示差粘度三检测联用技术表征了氘化聚苯乙烯、聚苯乙烯和氘化聚苯乙烯－ 聚异戊二烯。结果表明,在θ条件下,虽然氘化聚苯乙烯的化学依赖性常数υＴ,ＤＰＳ比聚苯乙烯的化学依赖性常数υＴ,ＰＳ大,但２５ ℃时在四氢呋喃中,氘化聚苯乙烯的分子尺寸仍小于聚苯乙烯的分子尺寸。由于嵌段共聚物的淋洗体积随组成变化,所以用传统的ＳＥＣ／ＲＩ得不到准确的分子量。经比较膜渗透、小角激光光散射和基质辅助激光脱吸与离子化时间飞行质谱等的实验结果,证明体积排斥色谱法／ 示差折光指数／ 直角激光光散射／ 示差粘度三检测技术能准确地得到氘化二嵌段共聚物的分子量以及其它重要信息。     

柚子皮衍生类蜂窝状碳材料在同步检测重金属离子中的应用

不含金属的碳材料通过廉价且易获得的柚子皮经KOH活化和高温热解获得,该碳材料具有高比表面积(1 055 m~2·g~(-1))和高石墨化程度的类蜂窝状结构。将多孔碳(PAC)材料修饰后的电极作为工作电极,采用阳极溶出伏安法(SWASV)同步检测Cd~(2+)、Pb~(2+)和Cu~(2+)离子,表现出较高的灵敏度、可重复性、稳定性和较低的检测限。研究认为PAC的微孔和中孔可以充当有效的离子传递通道,从而加速离子的扩散并显著提高交换效率,而高的石墨化程度提高了材料的导电性,加速了电子传输。     

Determination of Phosphatidylcholine in Shrimp by High-Resolution Mass Spectrometry

The molecular species of phosphatidylcholine from freshwater sources (Macrobranchium nipponense and Macrobranchium rosenbergii) and marine sources (Euphausia superba and Penaeus chinesis) were characterized by high-resolution mass spectrometry. The tandem secondary mass spectrometry (MS/MS) fragmentation allowed for the identification of fatty acyl residues of phosphatidylcholine molecular species. (16:0–18:1)Phosphatidylcholine was the main phosphatidylcholine molecular species determined in all shrimp samples, especially in E. superba. Macrobranchium rosenbergii phosphatidylcholine was particularly rich in (16:0–20:5)phosphatidylcholine and (16:0–22:6)phosphatidylcholine. The proportion of the two molecular species was next to the phosphatidylcholine of E. superba. Therefore, M. rosenbergii appears to be a potential freshwater source for the supplementation of polyunsaturated fatty acids, particularly eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6). This approach may be used as an efficient method for the identification of natural phosphatidylcholine sources from the broad range of plant, animal, and marine origins.     

基于5-氨基-1H-1,2,4-三唑-3-羧酸的锌(Ⅱ)/锰(Ⅱ)配合物的合成、晶体结构及性质

以5-氨基-1H-1,2,4-三唑-3-羧酸（HAtca）为配体,通过水热法和溶液扩散法分别合成了2个新的配合物[Zn（Athy） Br]_n（1,HAthy=5-氨基-1H-1,2,4-三唑-3-醇）和[Mn（Atca）₂（H₂O）₂]（2）。单晶结构分析表明配合物1和2分别属于正交和单斜晶系,结晶于Pbca和P2₁/c空间群。配合物1为2D层状结构,2是单核配合物。在配合物1中不存在氢键,而配合物2中含有丰富的氢键作用,并且通过氢键的作用形成了一个三维的网格结构。同时在固态下,配合物1和2分别在360、462 nm和382、402 nm处有较强的荧光发射峰。     

三维多孔核壳结构PdNi@Au催化剂的制备及对甲酸的电催化氧化

以K₂PdCl₄/K₂Ni(CN)₄为前驱体制备了具有凝胶特性的氰胶(Cyanogels), 利用硼氢化钠还原氰胶得到三维多孔珊瑚状PdNi合金前驱体, 在此基础上通过原位Galvanic置换反应, 制备得到内核为PdNi合金、 表面具有不同厚度Au层的三维多孔PdNi@Au催化剂. X射线衍射(XRD)分析和透射电子显微镜(TEM)观测结果显示, 该三维网状结构由粒径约7 nm的纳米颗粒相互连接形成; 能量分散光谱(EDX)线性扫描和元素分布(Mapping)分析显示该催化剂具有典型的核壳结构. 电化学测试结果表明, 表面Au层的厚度影响PdNi@Au催化剂的性能, 当Au的含量(摩尔分数)为5.6%时, 催化剂显示出对甲酸最佳的电催化活性, 对甲酸电催化氧化的峰电流密度达到商业化铂黑催化剂的7.2倍.     

A novel intumescent flame retardant imparts high flame retardancy to epoxy resin

Intumescent flame retardant (IFR) has received the considerable attention ascribed to the inherent advantages including non‐halogen, low toxicity, low smoke release and environmentally friendly. In this work, a novel charring agent poly (piperazine phenylaminophosphamide) named as PPTA was successfully synthesized and characterized by Fourier transform infrared spectra (FTIR) and X‐ray photoelectron spectroscopy (XPS). Then, a series of flame‐retardant EP samples were prepared by blending with ammonium polyphosphate (APP) and PPTA. Combustion tests include oxygen Index (LOI), vertical Burning Test (UL‐94) and cone calorimeter testing,these test results showed that PPTA greatly enhances the flame retardancy of EP/APP. According to detailed results, EP containing 10 wt% APP had a LOI value of 30.2%,but had no enhancement on UL‐94 rating. However, after both 7.5 wt% APP and 2.5 wt% PPTA were added, EP‐7 passed UL‐94 V‐0 rating with a LOI value of 33.0%. Moreover, the peak heat release rate (PHRR) and peak of smoke product rate (PSPR) of EP‐7 were greatly decreased. Meanwhile, the flame‐retardant mechanism of EP‐7 was investigated by scanning electron microscopy (SEM), thermogravimetric analysis/infrared spectrometry (TG‐IR) and X‐ray photoelectron spectroscopy (XPS). The corresponding results presented PPTA significantly increased the density of char layer, resulting in the good flame retardancy.     

One‐step synthesis of polysiloxane graft polyethylene mimic: Non‐expensive compatibilizer for polyethylene/polysiloxane blend

Polysiloxane/polyolefin copolymers have drawn much attention recently and emerged as a new group of functional polyolefin since they possess distinctive properties and find great potential applications in many areas (eg, compatibilizer, processing aid and surface modifier). However, traditional routes to synthesize polysiloxane/polyolefin copolymers generally require multi‐step labor‐consuming procedures. Herein, we report a novel one‐step synthesis of polydimethylsiloxane graft polyethylene (PDMS‐g‐PE) mimics. It was found that PDMS‐g‐PE mimics, namely vinylmethylsiloxane‐dimethylsiloxane‐(C30‐45 alkyl)methylsiloxane copolymers (short for VD‐AMS), could be formed via a one‐step synthetic procedure based on the siloxane equilibrium process between silanol‐terminated vinylmethylsiloxane‐methylsiloxane copolymer and (C30‐45 alkyl)methylsilicone. The chemical structures of VD‐AMS were characterized unambiguously using Fourier transform infrared spectroscopy, nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimetry. The correlation between reaction conditions and the structural parameters of VD‐AMS was established. Based on our experimental results, a plausible mechanism for the synthesis of VD‐AMS was proposed. Scanning electron microscopy micrographs showed that VD‐AMS could function as an efficient compatibilizer for immiscible PE/silicone blend. Given that the precursors of VD‐AMS are commercially available with low prices and that VD‐AMS can be easily synthesized under mild conditions, we believe VD‐AMS can represent as a competitive potential compatibilizer due to its relatively low cost.     

Development and Elucidation of a Pd‐Based Cyclization–Oxygenation Sequence for Natural Product Synthesis

Pd‐catalyzed sequences involving oxidative addition, cyclization, and termination through intermolecular nucleophile capture have tremendous utility. Indeed, they can generate a plethora of different polycyclic structures possessing a diverse range of functionality. However, one area of deficiency for Pd⁰/Pd^II variants is the ability to conclude them with oxygen‐based species. Inspired by the recent discovery of one such reaction in the course of a total synthesis program, we delineate herein that it has significant strength, both in terms of substrate scope as well as the terminating oxygen nucleophile. As a result, the reaction proved critical in achieving total syntheses of two oxygenated natural products, one of which was prone to over‐oxidation. Finally, a mechanistic proposal that accounts for its success is provided.     

钛酸锶光催化剂的改性研究进展

钛酸锶（SrTiO3）光催化剂是一种钙钛矿型三元氧化物,具有较强的氧化还原能力、良好的物理化学稳定性及环境友好等特点,在光催化各领域得到了广泛应用,如制氢/降解/光电催化等。SrTiO3对太阳光的利用率较低,且其本征光催化活性受光生载流子分离效率等因素限制,阻碍了实际应用。针对以上问题,将围绕国内外SrTiO3改性研究的现状进行综述,主要从掺杂、负载、复合改性等方面进行陈述。最后,对高效稳定SrTiO3光催化剂的未来发展趋势进行展望。     

双功能MoNi4电极实现水参与的氮杂环化合物转移氢化与脱氢

氮杂环的催化氢化在有机合成、药物研发、石油化工等领域有着重要应用.尽管发展了一系列均相和非均相催化加氢体系,但由于通常使用易燃易爆的氢气或价格昂贵且毒性较高的试剂(如:水合肼和硼氢化钠)为氢源,给安全生产及生态环境带来了严重的问题.此外,由于动力学同位素效应,氘代药物具有重要应用.氮杂环结构作为生物医药的构筑单元与关键中间体,现有的策略由于没有合适的氘源难以用于氘代氮杂环化合物的合成.因此,急需开发一种基于非贵金属催化剂和安全易得氢(氘)源的氮杂环催化氢(氘)化策略.水相中的电化学氢化可利用水电解原位产生的活性氢替代传统的氢气裂解实现有机氢化产物的合成,已成为一种理想氢化策略,被广泛应用于二氧化碳还原、硝酸根还原和生物质氢解等.本课题组前期研究已经实现了以氘水为氘源的氘代分子的高效电化学合成(Angew.Chem.Int.Ed.,2020,59,18527–18531;Angew.Chem.Int.Ed.,2020,59,21170–21175;CCS Chem.,2021,3,507–515).然而,要开发一种电化学的杂环氢化方法,一方面要克服氮杂环化合物对催化剂的毒化,另一方面要在电极表面产生大量的活性氢.因此,开发具有较好的水离解性能的非贵金属电极材料是实现氮杂芳烃电化学氢化和氘代的关键.基于上述要求,MoNi4(目前用于碱性电催化水分解制氢的活性较高的非贵金属材料)成为理想的电极材料.本文以喹喔啉(1,2,3,4-四氢喹喔啉骨架作为重要的结构单元存在于许多生物活性化合物中)作为模板底物,设计并制备了三维自支撑的MoNi4多孔纳米片为双功能电极,以水和氘水为氢源和氘源,实现了喹喔啉及其他氮杂环分子的氢化与氢化,同时实现了四氢喹喔啉的电化学氧化脱氢.制备了MoNi4纳米片阵列,利用扫描电子显微镜、透射电子显微镜、X射线衍射和X光电子能谱等手段进行表征,评估了其在碱性电解液中用于喹喔啉电化学转移氢化的性能.结果表明,MoNi4电极加速了动力学缓慢的Volmer步骤,在仅50 mV的过电势下以80％的法拉第效率实现了喹喔啉的电化学氢化.电子顺磁共振等证实水电解生成了H*,并与喹喔啉自由基阴离子偶联实现喹喔啉的氢化.同时,该电化学转移氢化方法可很好地应用于一系列喹喔啉衍生物和其他氮杂芳烃化合物.克级合成体现了该电化学转移氢化方法的潜在应用性.原位拉曼实验结果表明,在MoNi4表面形成的NiOOH是实现1,2,3,4-四氢喹喔啉氧化脱氢的重要物种.此外,以D2O代替H2O,可以较好的收率和高达99％的氘化率实现氘代氮杂环的合成.与传统的氮杂环氢化方法相比,本文的电化学转移氢化策略具有绿色、温和、高效的特点,同时拓宽了电化学氢化在合成化学中的应用.