热致相分离制备聚乳酸纳米纤维支架

本研究以二氧六环/叔丁醇为溶剂体系,采用热致相分离方法制备出具有多级孔径的三维连通的聚乳酸纳米纤维支架. 探讨了陈化、陈化温度、聚合物浓度、二氧六环/叔丁醇 (溶剂/非溶剂)比例对纳米纤维支架的结构和纤维直径大小的影响. 结果表明,陈化对较低聚合物浓度下(≤7%)纳米纤维结构的形成影响明显,而在较高聚合物浓度时(＞10%),只要控制在一定温度下相分离即可形成纳米纤维结构的支架;较低的陈化温度(≤5℃)有利于纳米纤维状网络结构(直径约20-300nm)的形成,且随着陈化温度的下降,纤维网络结构分布更加均匀;聚乳酸浓度增加, 纤维细化,网络结构分布更均匀,所形成的孔结构也更致密;叔丁醇含量≤12%时,纤维直径变化不大;当叔丁醇含量＞12%时,纤维直径明显增加(约500 nm).     

聚乳酸/壳聚糖纳米纤维结构形成的影响条件及其生物矿化活性

以二氧六环/冰醋酸为溶剂体系,采用相分离法制备了聚乳酸(PLA)/壳聚糖(CS)复合纳米纤维结构的组织工程支架,探讨了不同CS含量、不同凝胶温度及不同分子量对PLA/CS复合支架纳米纤维结构的影响以及支架的生物活性。结果表明,凝胶温度对PLA/CS复合材料的纳米纤维结构影响较大,且随着温度的降低,结构的微观尺寸也逐渐增大,从纳米级上升到普通的尺寸结构;CS含量对PLA/CS复合支架的基体结构影响不大;实验范围内PLA分子量对PLA/CS复合支架的纳米纤维结构有重要影响:分子量大的样品,较易得到PLA/CS复合纳米纤维结构的材料,而分子量小的样品则不能得到纳米纤维结构。另外,生物矿化实验表明CS的添加有利于PLA/CS复合材料生物活性的提高。     

聚富马酸丙二醇酯/羟基磷灰石复合多孔水凝胶的制备及其矿化性能研究

采用二步法合成了可降解的聚富马酸丙二醇酯(poly(propylene fumarate),PPF),并和N-乙烯基吡咯烷酮(N-vinyl pyrrolidone,NVP)共聚,以1,4-二氧六环为溶剂,通过改变溶剂的量制备了溶胀性能不同的PPF水凝胶.采用万能力学测试仪和扫描电子显微镜分别表征了水凝胶的压缩模量和形貌结构.选择20％ PPF和10％ NVP的聚合体系,预掺3％的纳米羟基磷灰石(hydroxyapatite,HA),以氯化钠粒子为致孔剂,制备了孔径在280～450 μm的纳米复合多孔水凝胶,使其压缩模量提高了61％.模拟体液矿化10天的结果显示,磷灰石成核位点的存在和良好的与外界液体环境物质交换的能力,促进了多孔水凝胶表面磷灰石的沉积,说明HA的复合可以有效提高PPF多孔水凝胶的成骨活性.     

原位聚合法制备具有温敏PNIPAM壳的核-壳结构聚合物纳米微球的研究

结合大分子自组装和原位自由基聚合方法,采用油溶性引发剂偶氮二异丁腈(AIBN),在聚(ε-已内酯)(PCL)纳米粒子表面引发聚合单体N-异丙基丙烯酰胺(NIPAM)和交联剂亚甲基双(丙烯酰胺)(MBA),制备得到了核-壳结构的PCL/PNIPAM聚合物纳米微球.系统研究了单体和交联剂用量、壳层目标交联度、初始PCL/DMF溶液的浓度及引发剂AIBN含量4个反应参数对核-壳结构PCL/PNIPAM纳米微球的PNIPAM壳层得率、微球尺寸、温敏性能及电镜形貌的影响.结果表明,在制备核-壳结构PCL/PNIPAM纳米微球的反应过程中,PCL粒子表面的聚合和水中的聚合二者之间相互竞争.适当增加引发剂AIBN的添加量,有利于制备得到核/壳比例可控的PCL/PNIPAM纳米微球;交联剂MBA较高的反应活性导致形成了非均匀交联的PNIPAM壳层.     

BPU/PLLA/DO体系的热力学性质对成膜过程及共混膜结构的影响

利用浸沉凝胶相转化法制备医用聚氨酯(BPU)/聚乳酸(PLLA)微孔膜,讨论了BPU/PLLA不同配比时聚合物/1,4-二氧六环/水三元体系的凝胶特性及其对共混膜结构和性能的影响,并初步探讨成膜机理.研究结果表明,随着BPU/PLLA质量比例由90/10变为75/25、50/50、25/75、10/90,聚合物/溶剂/非溶剂三元体系的热力学稳定性增强,凝胶值增大,但是共混溶液的黏度增大;并且,共混膜的孔隙率、膜厚、平均孔径、水蒸汽透过速率及吸水率先增加后降低.这主要是由于随着BPU/PLLA质量比例的变化,动力学扩散过程控制成膜速度转变为成膜体系热力学性质控制成膜速度;成膜过程由延时分相转变为瞬时分相,后又转变为延时分相.     

交联聚异丁烯酸甲酯型负载树脂的孔结构与分离稀土性能的关系

本文报导异丁烯酸甲酯型负载树脂的交联度、致孔剂组成和含量对负载树脂孔结构的影响.结果指出,良溶剂和劣溶剂按一定比例混合作为致孔剂,可制备不同孔结构的树脂.致孔剂量增加,树脂表观比重减小,而比表面积、孔体积与平均孔径均增加.交联度从10％增加到35%,表观比重和比表面积增加,而孔体积与平均孔径减小.增加致孔剂所含良溶剂的比例,树脂的表观比重、比表面积增加,而孔体积与平均孔径减小.已制备一系列不同孔结构的2-乙己基膦酸单2-乙己基酯(P507)负载树脂,比较了它们分离La、Ce、Pr、Nd的性能.结果表明,适当孔结构的负载树脂用于萃取色层分离稀土元素具有优良的分离性能.     

P(VdF-HFP)-ILs基多孔纤维凝胶电解液的制备

以偏氟乙烯-六氟丙烯共聚物P(VdF-HFP)为成纤聚合物,聚乙烯吡咯烷酮(PVP)为致孔聚合物,制备得到P(VdF-HFP)/PVP混合静电纺丝纤维。然后利用成纤聚合物和致孔聚合物水溶性的差异,采用超声波辅助水致相分离法,去除水溶性PVP,得到非水溶性P(VdF-HFP)骨架的多孔超细纤维。扫描电子显微镜、孔隙结构分析和显微镜相图分析等结果显示,调节混合静电纺丝纤维中PVP含量,可以得到具有不同中孔/大孔结构的多孔超细纤维膜。以P(VdF-HFP)基多孔超细纤维吸附离子液体(ILs)制备得到凝胶电解液,测试其电化学性能,结果显示由P(VdF-HFP)∶PVP=5∶3静电纺丝纤维制备的P(VdF-HFP)-ILs基多孔超细纤维凝胶电解液显示出宽电化学窗口(3.6 V)、高电导率(0.84 mS·cm~(-1))和较高的持液量(295 wt%)。     

静电纺丝制备碳纳米管基复合纳米纤维的研究进展

碳纳米管(CNTs)作为增强材料与聚合物复合制成纳米纤维,有助于提高纳米纤维性能,扩展其应用领域。本文综述了近年来国内外静电纺丝制备CNTs基复合纳米纤维的研究现状,重点介绍了CNTs/PAN复合纳米纤维、CNTs/PANI/PEO复合纳米纤维、CNTs/PVA复合纳米纤维、CNTs/PA复合纳米纤维、CNTs/TiO2复合纳米纤维的研究进展及其在纳米传感器、电磁干扰、超级电容器、染料敏化太阳能电池(DSSCs)、组织工程支架、药物控制释放等方面的应用潜力,展望了CNTs基复合纳米纤维的发展前景。     

较细ZnS:Mn/PVP纳米纤维的制备及表征

采用静电纺丝的方法制备了ZnS:Mn/Polyvinylpyrrolidone复合纳米纤维.使用的溶剂为水、乙醇及DMF(N,N-Dimediylfommnide),的使用有助于制备较细的纤维,电纺溶液中随着聚合物PVP浓度降低,纤维的直径变小,当PVP质量分数为6.6%时,纤维的直径是80 nm,通过荧光显微镜和荧光...     

具有抗菌性能的载药复合微纳米纤维的制备及其结构和性能表征

利用静电纺丝技术制备了一种具有抗菌性能的氧化锌(ZnO)/聚乳酸(PLA)/聚己内酯(PCL)载药微纳米纤维膜,并通过扫描电子显微镜(SEM)、X射线衍射(XRD)和傅里叶变换红外光谱(FTIR)分别对复合膜的表面形态、元素组成和化学结构进行表征。通过抗菌实验评价了复合膜的抗菌性能,用紫外分光光度计测试复合膜在体外的药物释放行为。结果显示,以物理共混的方式将ZnO和氢溴酸高乌甲素(LAH)成功载入复合微纳米纤维;与PLA/PCL复合微纳米纤维膜相比,ZnO/PLA/PCL复合微纳米纤维膜表现出更好的抗菌效率。当ZnO含量为10%(wt)时,复合微纳米纤维膜具有最佳的抗菌性能;药物释放性能结果表明,ZnO/PLA/PCL复合微纳米纤维膜具有良好的药物缓释性能。     

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.