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。     

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.     

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。     

纳米结构型PMAA/CdS复合微球的微凝胶模板法制备研究

以微凝胶为模板,利用微凝胶三维网络结构对无机沉积反应的限域和导向作用,制备了具有核-壳结构的聚甲基丙烯酸/硫化镉(PMAA/CdS)有机/无机复合微球材料.复合微球的制备包含两个基本步骤首先,以反相乳液聚合法得到包含Cd(Ac)2的聚甲基丙烯酸微凝胶;然后,在搅拌过程中向反应体系中缓慢通人H2S气体,使镉离子沉积为CdS,经洗涤处理后得到PMAA/CdS复合微球.SEM观察表明,复合微球表面呈现均一的微纳米结构,这种结构可因微球制备条件的不同而不同.而且,超声处理可使微球表面趋于光滑.X射线衍射分析表明复合微球中CdS处于晶态,具有立方结构.此外,复合微球因CdS的存在而具有光致发光特性.     

聚合物纳米微球增韧水凝胶的制备与表征

通过无皂乳液聚合制备阳离子纳米微球(NPs),并将其作为疏水交联中心来制备高强韧水凝胶。体系中的疏水单体甲基丙烯酸月桂酯(LMA)在表面活性剂作用下聚集到纳米微球表面,形成疏水缔合中心,通过原位引发自由基聚合得到纳米微球杂化的聚丙烯酰胺疏水缔合水凝胶P(AAm-LMA)-NPs。当凝胶受到应力时,由纳米微球形成的动态交联点通过断裂与重组可以有效地耗散能量,极大地提高了凝胶的强度和韧性。因此,所制备的P(AAm-LMA)-NPs水凝胶表现出十分优异的机械性能,其最大拉伸强度可达860 kPa,断裂伸长率为1280%,断裂韧性为3.8 MJ/m³。聚合物纳米微球增韧水凝胶的力学性能优异,有望在生物医学和工业领域有重要应用。     

制备核-壳结构聚合物纳米微球和空心球的原位聚合方法的普适性研究

采用原位聚合制备核-壳结构聚合物纳米微球和空心球的新方法, 利用甲基丙烯酸2-羟丙酯(HPMA)和乙酸乙烯酯(VAc)两种单体, 在类似的反应条件下, 成功地制备了以聚(ε-己内酯)(PCL)为核, 分别以交联PHPMA和PVAc为壳的纳米微球; 将微球的核酶解后, 分别得到了对应的交联PMAA空心球和交联PVA空心球. 结果表明, 原位聚合制备核-壳结构聚合物微球的新方法具有一定的普适性, 适用于单体可溶于水而生成的聚合物不溶于水的体系.     

模板聚合法制备高浓度PMAA/HEC核-壳聚合物纳米微球

以羟乙基纤维素(HEC)为大分子模板,选用甲基丙烯酸(MAA)单体,通过模板聚合一步反应,制备了较高浓度(40 mg/mL)的核-壳结构聚合物纳米微球溶液。采用透射电镜、红外光谱、粒径-电位和荧光光谱等分析方法,研究了PMAA/HEC纳米微球的形态、结构、原位形成机理和pH响应特性。结果表明:在大分子间氢键作用的驱动下,原位生成的PMAA和HEC自组装形成了以不溶性的PMAA/HEC大分子复合物为核、以可溶性HEC为壳的PMAA/HEC聚合物纳米微球。微球在pH=0.7~4.0范围内表现出较明显的pH敏感性。     

磁性微球的制备及应用

磁性微球在生物医学和分离工程等多个领域都有广泛的应用,如固定化酶、靶向药物载体、核磁共振成像、细胞标记及分离、核酸和蛋白质分离纯化、环境治理等.近年来随着纳米新材料及制备工艺的不断创新,磁性微球的制备及应用都取得了大量进展.磁性微球的制备方法主要可以分为4类:(1)包裹法,在微球生成的同时将磁性纳米颗粒包裹在微球基质内,又可以细分为异质聚合法、乳化-溶剂挥发法、膜乳化和微流控技术、反相悬液-交联法、Stober法、聚合诱导胶体聚集法等;(2)模板组装法,在模板微球内部或表面组装磁性纳米颗粒,包括溶胀法、吸附法和静电自组装法等;(3)模板原位生成法,在模板微球的内部或表面原位生成磁性纳米颗粒,包括共沉淀、沉淀-氧化法、有机前驱体热分解法等;(4)溶剂(水)热法,以有机溶剂或水为介质,密闭体系中的反应物在一定的温度和溶液的自生压力下反应得到磁性微球.本文按照制备方法对近几年来磁性微球领域的研究进展进行了总结,包括反应原理、磁性微球的性质、表面功能化和应用介绍.     

聚甲基丙烯酸甲酯-氯化银复合纳米微球的制备及其摩擦学性能

采用原位种子乳液聚合法合成了聚甲基丙烯酸甲酯 氯化银(PMMA AgCl)核壳结构复合纳米微球,通过透射电镜(TEM),红外光谱(IR),热分析(TG DTA)和X射线粉末衍射(XRD)等测试手段对其结构及性能进行了表征.在四球试验机上对其摩擦学行为进行了考察,研究结果表明,PMMA AgCl核壳结构复合纳米微球用作润滑油添加剂具有良好的抗磨性能,能显著提高基础油的失效负荷.     

壳交联pH响应型PLGA载药微球的制备与研究

首先采用一次乳化法制备出PLGA[聚(乳酸-羟基乙酸)]纳米微球,并通过静电吸附将阳离子聚合物壳聚糖修饰到PLGA微球表面,然后以香草醛为交联剂对壳聚糖进行化学交联,得到一种壳交联的p H响应型纳米微球(PCV),微球粒径为(277.60±38.01)nm,表面电位为(21.60±4.51)m V.微球稳定性评价结果显示微球在24 h内粒径变化较小;流式细胞仪检测显示细胞对PCV微球的摄取量比未经修饰的PLGA微球的摄取量高;空白微球细胞毒性实验表明在空白微球浓度小于80μg/m L时细胞的存活率达93.24%.以多西他赛(DTX)为模型药物进行包载,该纳米微球DTX的载药率为7.48%,包封率为34.98%;体外药物释放实验显示,该微球在p H=5.0环境下孵育90 h的药物积累释放率达58.66%,而在p H=7.4的环境下的药物积累释放率为50.63%;此外,载DTX微球毒性试验结果表明该载药微球对A549肺癌细胞有较强的杀伤作用,其IC50值可达0.0009μg/m L.     

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.     

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.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.