聚己内酯接枝淀粉纳米晶的制备

通过异氰酸酯与端羟基聚己内酯反应制备端异氰酸酯基预聚体,再接枝到淀粉纳米晶表面,制备了端基分子量可控的聚己内酯接枝淀粉纳米晶。分别用FTIR和1H NMR对所制备的聚己内酯接枝淀粉纳米晶进行表征,结果表明,有少量聚己内酯接枝到淀粉纳米晶表面。XRD结果表明,接枝了少量聚己内酯后的淀粉纳米晶的晶型和结晶度与未接枝的淀粉纳米晶基本一致。聚己内酯接枝淀粉纳米晶的熔融温度由115℃左右提高到122℃左右,并且温度范围变宽。浸润性实验表明,聚己内酯接枝淀粉纳米晶与水不浸润,其表面已具有疏水性。聚己内酯仅接枝在淀粉纳米晶的表面,改善了淀粉纳米晶表面的疏水性能和与聚酯类聚合物的界面相容性。聚己内酯接枝淀粉纳米晶有望用于可降解聚酯类高分子材料,如聚乳酸(PLA)、聚己内酯(PCL)、聚丁二酸丁二醇酯(PBS)等,改善其力学性能和生物降解性能等。     

单分散铁氧体纳米颗粒的生长机制与成分偏聚的透射电子显微研究

理解纳米晶的生长机制对单分散纳米晶的可控合成至关重要。本文以热分解法制备的双金属铁氧体(钴铁氧和锰铁氧)纳米颗粒为例,利用透射电子显微镜(TEM)系统研究了铁氧体纳米晶的生长机制,揭示了由此造成的成分偏聚现象。对不同时间阶段的反应产物的分析结果表明,两步加热法(即先后在相对低的温度和相对高的温度下加热反应)是制备高质量的单分散铁氧体纳米晶的关键;通过控制低温反应阶段的时间可实现纳米晶的形核阶段和生长阶段的有效分离,从而有利于单分散纳米晶的合成。利用扫描透射电子显微镜(STEM)及电子能量损失谱(EELS)谱学成像技术分析,我们进一步发现了双金属铁氧体纳米晶中的成分偏聚现象,表明双金属铁氧体纳米晶在形核阶段主要形成富Fe的核芯,而在生长阶段则形成更富Co/Mn的双金属铁氧体壳层。这些结果对制备高质量的单分散铁氧体纳米晶具有重要的指导意义,同时也有助于正确理解热分解法制备的铁氧体纳米晶的表面成分和相关表面物理化学性质。     

聚己内酯接枝淀粉纳米晶的制备

本文通过异氰酸酯与端羟基聚己内酯反应制备端异氰酸酯基预聚体,再接枝到淀粉纳米晶表面,制备了端基分子量可控的聚己内酯接枝淀粉纳米晶。分别用FTIR和1HNMR对所制备的聚己内酯接枝淀粉纳米晶进行表征,结果表明有少量聚己内酯接枝到淀粉纳米晶表面。XRD结果表明,接枝少量聚己内酯的淀粉纳米晶的晶型和结晶度基本不变。聚己内酯接枝淀粉纳米晶的熔融温度由115℃左右提高到122℃左右,并且温度范围变宽。浸润性实验表明,聚己内酯接枝淀粉纳米晶与水不浸润,其表面已具有疏水性。聚己内酯仅接枝在淀粉纳米晶的表面,改善了淀粉纳米     

甲基丙烯酸丁酯在纳米TiO2表面的原位接枝

利用分子自组装技术,对纳米TiO2粒子表面组装上有机单分子层,使其带上不饱和基团C=C,在自组装单分子层表面原位引发甲基丙烯酸丁酯（BMA）单体聚合反应,使纳米TiO2表面形成化学键合的聚合物层,达到对纳米TiO2粒子改性的目的。讨论了不同反应条件对接枝聚合率的影响,通过FTIR、TG-DTA等分析手段,研究聚合改性物质的结构和改性后纳米TiO2粒子的分散稳定性。实验发现聚合改性后的纳米TiO2在有机相中有良好的分散性。     

淀粉基高分子材料的研究进展

概述了近5年国内外在淀粉的化学、物理改性及其作为一种材料使用方面取得的最新研究进展.淀粉的化学改性主要介绍了淀粉的酯化、醚化、氧化、交联、接枝共聚等,而物理改性主要介绍了淀粉分别与黏土、脂肪族聚酯、聚乙烯醇以及纤维素等天然大分子的共混改性,同时还介绍了通过酸化制备淀粉纳米晶.淀粉基材料除了用于制备可生物降解塑料、吸附材...     

低分子量氯磺化聚乙烯对纳米Si3N4粉体表面处理

用降解氯磺化聚乙烯橡胶(CSM)的方法制备了低分子量氯磺化聚乙烯(LMCSM),将其作大分子表面改性剂对纳米氮化硅(Si3N4)粉体进行表面修饰,对改性前后的纳米Si3N4粉体采用沉降实验、FT-IR、TEM、TGA等方法进行了表征. 结果表明,LMCSM对纳米Si3N4粉体的改性主要为化学改性,其化学利用率为54%,物理利用率为29%;改性后的纳米Si3N4粉体的表面自由能从142.6 J/M2降至66.89 J/M2,在三氯甲烷中分散良好.     

配体交换调控纳米金表面寡核苷酸自组装

以4-巯基苯甲酸(MBA)为调控分子,对照巯基己醇(MCH),基于配体交换法对纳米金(10 nm)表面的寡核苷酸(DNA)自组装进行调控,并用凝胶电泳进行表征.结果表明,在纳米金表面,MCH能完全取代DNA.当MCH与纳米金的摩尔比达到2400:1后,纳米金发生凝聚,MBA不能完全取代DNA;MBA和DNA的二元组装层能使纳米金在水溶液中稳定分散.另外用DNA取代MBA的反应比用MBA取代DNA的反应更容易进行.     

用于透射电子显微镜表征的单层纳米晶/聚合物复合薄膜的制备

为了提高纳米晶的TEM表征质量, 通过在水/气两相界面上铺展纳米晶/聚合物复合单层膜的方法, 制备了质量较高的TEM样品. 对于水相纳米晶采用表面活性剂再包覆的方法, 将其转移到油相. 与传统制样方法(尤其是水相合成纳米晶)相比, 嵌入聚合物膜中的纳米晶更容易分散(受到空间位阻与分子间弱相互作用等因素的影响), 并且聚合物膜可以自支持在空的铜网上, 从而提高了TEM照片的清晰度. 研究了系统中聚合物、纳米晶、表面活性剂和溶剂的种类及配比关系对于样品和成像质量的影响, 结果表明, 该方法对各种金属及半导体纳米晶的TEM表征具有一定的普适性.     

NaYF_4:Yb~(3+),Er~(3+)上转换发光纳米晶在三元混合溶剂体系中的配体交换修饰及发光性质

选用2-胺乙基膦酸双官能团小分子作为配体交换剂,采用氯仿/乙醇/水三元混合溶剂体系下的配体交换修饰方法,解决了疏水纳米晶与亲水配体的有效接触反应问题,实现了上转换纳米晶的水溶性以及表面胺基功能化修饰.通过傅里叶变转换红外光谱和热重分析证实了表面配体分子的替换.透射电子显微镜和激光粒度分析结果显示,所得水溶性纳米晶具有粒径均一,水力直径小和分散稳定的特点.样品的发射光谱结果表明,配体交换过程对纳米晶的发光无明显影响,保持了良好的发光性能.通过荧光共聚焦成像技术实现了胺基修饰上转换发光纳米晶对HeLa细胞的光学成像,证实所得纳米晶适合于潜在的生物学应用.     

疏水上转换纳米晶的均相体系聚合物包覆及在发光检测中的应用

选用水解的十八碳烯-马来酸酐共聚物(PMAO)为表面修饰分子,发展了一种以疏水纳米粒子吸附表面活性剂十二烷基磺酸钠(Na YF_4-SDS)为中间体的均一液相聚合物包覆纳米粒子方法.该方法解决了油溶性纳米晶与弱极性聚合物分子难以在单一体系下均匀分散的问题,实现了在均一液相体系下对疏水纳米晶的单分散包覆以及表面羧酸官能团修饰.红外光谱与表面Zeta电位测试结果表明纳米晶已被聚合物包覆,粒子表面为强电负性的羧酸基团.电镜结果表明聚合物包覆的上转换纳米晶粒径无明显的变化,具有良好的单分散性.发射光谱表明聚合物包覆前后粒子的发射谱带无显著变化,保持了原油相粒子的发光性能.进一步的特异性识别荧光显微成像实验证实聚合物包覆后的粒子(Na YF_4-PMAO)可用于生物学检测.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.