聚甲基丙烯酸单层保护金纳米粒子的制备及pH响应性聚集

通过可逆断裂链转移加成聚合,制备了单分散的聚甲基丙烯酸叔丁酯,并一步水解获得了具有硫醇端基的聚甲基丙烯酸(PMAA).在还原氯金酸为金纳米粒子的同时,利用硫醇端基与金纳米粒子(GNPs)的耦合作用,一步获得了聚甲基丙烯酸单层保护的金纳米粒子.通过紫外光谱和透射电镜表征证实,金纳米粒子为单分散的球型颗粒,在水溶液中具有长期稳定性.聚甲基丙烯酸单层保护的金纳米粒子的光学性质和聚集状态,具有明显的pH响应性.在酸性条件下,由于PMAA被质子化发生疏水性转变,聚合物链收缩聚集,促使金纳米粒子之间互相靠近并聚集,其表面等离子共振吸收峰发生红移.从酸性调节为碱性后,(PMAA-@-GNPs)能重新分散,吸收峰发生蓝移.在多次循环后,溶液的光学信号能可逆互变且变化不大.     

聚甲基丙烯酸基纳米水凝胶的“绿色”合成

利用原位生成的聚甲基丙烯酸甲酯种子乳胶模板以及表面活性剂与功能单体间的正负电荷作用,发展了一种可在全水相中“绿色”合成聚甲基丙烯酸(PMAA)基纳米水凝胶的新方法.利用动态光散射法、ξ-电位测定、FTIR和TEM对纳米水凝胶的尺寸及其分布、表面电荷、组成、形态、结构和pH响应行为进行了表征.结果表明,PMAA基纳米水凝胶具有聚甲基丙烯酸甲酯内核和交联聚甲基丙烯酸外壳的核壳结构.当甲基丙烯酸(MAA)的用量由2 mL增至3 mL时,PMAA基纳米水凝胶的尺寸变大.当MAA的用量增加至5 mL时,反应体系中除了生成PMAA基纳米水凝胶外,还生成了PMAA次级粒子.PMAA基纳米水凝胶表现出良好的pH响应性:当介质的pH值由2增加至7时,其流体力学体积扩张了近80倍.     

聚甲基丙烯酸单层保护金纳米粒子选择性检测Pb2+

以聚甲基丙烯酸单层保护的金纳米粒子(GNPs)作为传感器, 实现了水溶液中Pb²⁺的选择性循环检测.先采用柠檬酸钠还原法获得尺寸均匀的GNPs, 再通过具有硫醇端基的聚甲基丙烯酸与金的强耦合作用, 获得了聚甲基丙烯酸单层保护的金纳米粒子(PMAA-@-GNPs).动态光散射、紫外-可见吸收光谱及透射电子显微镜表征证实了其单层结构.在Pb²⁺的诱导下, PMAA-@-GNPs溶液颜色从酒红色变为紫色并可肉眼识别.透射电子显微镜结果证实, 这种变化是由于Pb²⁺交联羧基使聚合物发生收缩, 并诱导GNPs的聚集所致.对比Pb²⁺与Hg²⁺, Mg²⁺, Cu²⁺, Zn²⁺, Na⁺, Ni²⁺, Fe³⁺, Cd²⁺, K⁺和Fe²⁺溶液颜色的变化, 证实此体系具有一定的选择性.用EDTA可夺取交联的Pb²⁺, 使PMAA-@-GNPs 的吸收峰恢复并可用于循环检测Pb²⁺.     

新型核壳结构水凝胶的合成与表征

以羟丙基纤维素为模板,在水溶液中合成了不含表面活性剂的聚甲基丙烯酸（PMAA）纳米水凝胶。再以该PMAA纳米水凝胶为模板,合成了具有pH和温度双重敏感的聚甲基丙烯酸/聚N-异丙基丙烯酰胺（PMAA-PNIPA）核壳结构纳米水凝胶。对纳米水凝胶的形态、结构、pH以及温度敏感性的表征结果表明,纳米水凝胶粒径为338.8～407.9 nm,并随交联剂用量的增加而减小,其体积相转变具有良好的pH及温度响应性,这种绿色合成的生物相容性新型核壳结构纳米水凝胶具有极为广泛的应用前景。     

聚甲基丙烯酸纳米水凝胶的水相合成及其磁性功能化

利用十二烷基硫酸钠/吐温20复配表面活性剂和原位生成的聚甲基丙烯酸甲酯(PMMA)种子乳胶,发展了一种可在全水相中"绿色"合成较高浓度的聚甲基丙烯酸(PMAA)纳米水凝胶的新方法.以PMAA纳米水凝胶为前驱体,采用原位氧化沉淀法制备了磁性PMAA纳米微球.利用动态光散射法、FTIR分析、TEM观察、振动样品磁强计测试(VSM)、热重分析(TG)等对纳米水凝胶和磁性微球进行了表征,并探讨了PMAA纳米水凝胶的形成机理.结果表明,吐温20与MAA和PMAA间的氢键作用,促成了交联PMAA/吐温20复合物层在PMMA种子乳胶表面的选择性生长,导致生成了具有核壳结构的PMAA纳米水凝胶.PMAA纳米水凝胶表现出良好的p H响应性,当介质的p H值由1增加至6时,其流体力学体积扩张了近50倍.磁性PMAA纳米微球具有超顺磁性,其饱和磁化强度高达50 A·m~2/kg.     

pH响应性表面对蛋白质吸附的调控

通过表面引发原子转移自由基聚合在固定了引发剂的硅表面接枝了聚甲基丙烯酸叔丁酯(PtBMA),而后通过水解得到聚甲基丙烯酸(PMAA)聚合物刷.通过X射线光电子能谱、椭圆偏振仪和水接触角测试证明了接枝改性的成功.研究发现PMAA改性表面的浸润性和对蛋白质的吸附行为都具有一定的pH响应性.在较低pH值时改性表面相对疏水,随...     

PMAA纳米水凝胶的水相制备

利用表面活性剂间的疏水作用以及表面活性剂与单体间的氢键作用,促使甲基丙烯酸(MAA)单体在原位生成的聚甲基丙烯酸甲酯(PMMA)种子乳胶表面的选择性聚合,实现了PMAA纳米水凝胶的水相"绿色"制备。利用动态光散射、傅里叶红外光谱、透射电子显微镜表征了PMAA纳米水凝胶的尺寸、组成、形貌和pH响应性。研究了聚氧乙烯失水山梨醇单月桂酸酯(吐温20)的用量、N,N’-亚甲基双丙烯酰胺(MBA)的用量、MAA的用量和加入方式、十二烷基硫酸钠(SDS)的补加速率等对PMAA纳米水凝胶的尺寸和溶胀性能的影响。结果表明:PMAA纳米水凝胶为核-壳结构;随着MBA用量的减小、吐温20用量的增加、MAA用量的增加,PMAA纳米水凝胶的尺寸和溶胀比均增大;当采用半连续加入MAA时,PMAA纳米水凝胶的尺寸和溶胀比变小;当SDS的补加时间由60min延长到100min时,PMAA纳米水凝胶的尺寸逐渐变小。PMAA纳米水凝胶具有良好的pH响应性,当介质的pH从1增加到6时,其流体力学体积扩张了64倍。     

酶促缩聚和原子转移自由基聚合法合成AB型两亲性嵌段共聚物

Novozyme-435催化10-羟基癸酸进行自缩聚反应得到线性聚酯, 端基分别是羟基(—OH)和羧基(—COOH), 在三乙胺催化下, 分别用α-溴代丙酰溴和三甲基氯硅烷(TMSCL)进行端基官能化生成一个单官能度的大分子引发剂, 在CuCl/2,2'-联吡啶(bpy)催化体系中, 引发甲基丙烯酸环氧丙酯(GMA)的原子转移自由基反应(ATRP), 得到聚(10-羟基癸酸酯)/聚甲基丙烯酸环氧丙酯(PHDA-b-PGMA) AB 型两亲性嵌段共聚物, 其结构及分子量(分布)通过核磁共振和凝胶渗透色谱(GPC)确证. 此AB型两亲性嵌段共聚物在水溶液中能自组装形成纳米粒子, 用原子力显微镜(AFM)观察粒子的形状和大小.     

pH和温度诱导双亲水嵌段共聚物聚甲基丙烯酸-b-聚N-(2-甲基丙烯酰氧乙基)吡咯烷酮水溶液的胶束化（英文）

基于可逆加成裂解链转移自由基(RAFT)聚合法开发了一系列新型双亲水嵌段共聚物——聚甲基丙烯酸-b-聚N-(2-甲基丙烯酰氧乙基)吡咯烷酮(PMAA-b-PNMP),并利用凝胶渗透色谱法(GPC)和~1H NMR对其结构进行了表征。光散射和冷冻电镜的结果表明,此类双亲水嵌段共聚物的水溶液具有pH和温度诱导胶束化的现象,而且PNMP的聚合度对胶束化的pH和温度影响都非常大。一般而言,PNMP的聚合度越大,胶束化的pH值越小,胶束化的温度则越高。pD相关的~1H NMR结果表明,PNMP与PMAA片段和水分子之间氢键的削弱以及PNMP与PMAA链之间相互作用的增强是pH诱导PMAA-b-PNMP胶束形成的主要原因,而PNMP片段与水分子之间氢键的削弱则是温度诱导PMAA-b-PNMP胶束形成的主要原因。此外,我们发现在PMAA-b-PNMP体系中制备的纳米金颗粒的大小可通过溶液pH进行可控调节。总体而言,pH值越高,金纳米颗粒的粒径越小。     

含有金纳米粒子的筛分介质对不同长度DNA片段的毛细管电泳分离

探讨了含有金纳米粒子(GNPs)的筛分介质在毛细管电泳(CE)中对不同长度DNA片段的分离.以聚环氧乙烷(PEO)-金纳米粒子(GNPs)-TBE为CE筛分介质,用涂层的毛细管柱(37 cm×75 μm,有效长度27 cm)分离DNA Marker D和1 kbp DNA Ladder Marker标准DNA片段,考察了CE过程中各参数(如筛分介质质量浓度、分离电压、温度和筛分介质pH值)对不同长度DNA片段分离的影响.对比了新型筛分介质与不含GNPs的PEO-TBE筛分介质的分离效果,并将新型筛分介质用于实际样品的检测.结果表明,在筛分介质中添加GNPs后能够改进CE的分离效果,且分离时间短.方法较适于分离较宽范围的DNA片段.     

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%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

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.     

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.     

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.     

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.     

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.