AOPAN/PA-66复合纳米纤维膜的制备及对金属离子的吸附性能

采用双喷头电纺丝技术,将尼龙(PA-66)纤维增强的聚丙烯腈(PAN)纳米纤维膜(PAN/PA-66)与盐酸羟胺进行偕胺肟化反应,制备了一种偕胺肟化聚丙烯腈/尼龙复合纳米纤维膜(AOPAN/PA-66).通过红外光谱及扫描电子显微镜等方法研究了偕胺肟化前后纳米纤维膜的组成、形貌和力学性能;并考察了AOPAN/PA-66复合纳米纤维膜对铜离子和铅离子的吸附性能.结果表明,AOPAN/PA-66复合纳米纤维膜的抗拉伸强度及断裂伸长率分别为4.73 MPa和30.76%,对Cu(Ⅱ)及Pb(Ⅱ)的吸附量分别为67.5和75.4 mg/g.     

PVA/GA/β-CD纳米纤维的制备及染料吸附性能

利用静电纺丝技术,以六氟异丙醇(HFIP)和水为溶剂,制备了环糊精(β-CD)含量为70%(质量分数)的聚乙烯醇(PVA)/β-CD纳米纤维,并经戊二醛(GA)交联处理得到了可用于染料吸附的PVA/GA/β-CD纳米纤维.通过红外光谱和扫描电子显微镜研究了交联反应前后纳米纤维组成和形貌的变化;考察了PVA/GA/β-CD纳米纤维对7种水溶性染料的吸附性能.结果表明,PVA/GA/β-CD纳米纤维对孔雀石绿、甲基紫和刚果红的吸附效果较好,最大吸附量分别为124.71,121.14和127.39 mg/g,4次吸附-解吸附循环后,染料去除率仍保持80%左右,在染料废水处理中具有良好的应用前景.     

纳米储能纤维复合过滤膜的制备及性能

以静电纺丝技术制备的同轴聚甲基丙烯酸十八烷基酯(PSMA)/聚对苯二甲酸乙二酯(PET)纳米储能纤维为支撑层,经聚偏氟乙烯(PVDF)涂覆成膜和溶剂化处理,制备了一种低压高水通量的纳米储能纤维复合过滤膜(NFCM),其中以水或乙醇为凝固溶液的复合过滤膜分别记为NFCM@H2O或NFCM@EtOH.分析并讨论了不同溶剂处理方式对NFCM力学性能和表面形貌的影响,表征了膜的纯水通量和抗污性能,用扫描电子显微镜(SEM)观察了膜的横断面形貌.结果表明,PSMA/PET纳米储能纤维具有明显的吸放热行为,熔融温度和热焓值分别为36.5℃和10.7J/g,NFCM的熔融温度和热焓值分别为36℃和2.7J/g.NFCM的形貌结构、纯水通量和截留率与溶剂处理方式相关,NFCM@EtOH膜的水通量介于100~1400L/(m2·h)之间,而NFCM@H2O膜的水通量仅在40~220L/(m2·h)之间.NFCM的拉伸强度由初始0.925MPa(PVDF)提高到4.28MPa以上.NFCM中的相变材料对膜过滤性能有重要影响,并在过滤温度低于50℃时具有减缓作用.     

聚羟基丁酸酯/碳纳米管复合纳米纤维膜的制备及其对重金属离子吸附分离性能的研究

以聚羟基丁酸酯和碳纳米管为原料,采用三氯甲烷/二甲基甲酰胺混合溶液为溶剂,利用静电纺丝技术制备了聚羟基丁酸酯/碳纳米管复合纳米纤维膜.研究了碳纳米管的含量对纳米纤维膜形貌和力学性能的影响,探讨了复合纳米纤维膜对重金属Cu(II)、Cd(II)和Pb(II)的吸附特性.实验结果表明:加入1 wt%碳纳米管能够将纳米纤维的平均直径从(728±146)nm降低至(468±89)nm,纳米纤维膜的比表面积从27.24 m~2/g提高至43.45 m~2/g;碳纳米管的复合能够有效增强聚羟基丁酸酯纳米纤维,当碳纳米管含量1 wt%为最佳,拉伸强度可达5.85 MPa,较纯聚羟基丁酸酯纳米纤维提升了115%.复合纳米纤维膜对重金属离子具有良好的吸附特性,其对Cu(II)、Cd(II)和Pb(II)的最佳吸附pH值为5,此时最大吸附容量分别为91.04、171.05和197.03mg/g,平衡吸附时间分别约为50、60和60 min,吸附率分别为1.79、2.83和3.28 mg/g/min;热力学和动力学分析表明,复合纳米纤维膜对重金属Cu(II)、Cd(II)和Pb(II)的吸附行为更符合Freundlich模型,吸附过程更符合Pseudo-second order模型;循环使用实验表明,重复使用5次后,其吸附容量可保持在初始值的87%以上,具有较好的使用寿命.     

稳定射流电纺丝法制备定向排列的壳聚糖超细纤维

采用电驱动纺丝,以壳聚糖(CTS)为研究对象材料,通过引入超高分子量聚氧化乙烯(PEO)调节纺丝液的黏弹性,实现抑制电纺丝固有的射流不稳定弯曲摆动来得到单一的稳定射流,从而可以像传统工业上的干、湿法纺丝一样制备定向的超细CTS纤维(称为稳定射流电纺丝,SJES).系统地研究了SJES的工艺参数(如CTS/PEO质量比、纺丝电压、接收距离、凝固浴成分、辊筒转速等)对制备定向的超细壳聚糖纤维的影响,并通过SEM、FTIR、WAXD、纳米力学拉伸仪等研究了所制备纤维的形貌、结构与性能.结果表明,SJES法制备的CTS纤维直径在10μm以下,优化参数(如电压和辊筒转速)可使纤维直径细化到3μm左右.纤维单丝具有较高的力学性能,断裂强度和纤维模量可以分别达到(762±93)MPa和(11±6)GPa.稳定射流电纺丝方法制备的超细纤维与常规电纺丝法制备的纤维相比,具有较高的微晶取向度.     

抗污染PVA/PVDF电纺纳米纤维复合超滤膜的制备及过滤性能

以聚对苯二甲酸二醇酯(PET)无纺布为基底,聚偏氟乙烯(PVDF)纳米纤维为支撑层,聚乙烯醇(PVA)纳米纤维膜为分离层,采用静电纺丝法制备超滤膜,并用水/丙酮混合溶液对复合纳米纤维膜表面进行溶液处理,再加入戊二醛交联改性得到致密分离层.采用扫描电子显微镜(SEM)和红外光谱(FTIR)表征了复合超滤膜的表面,用水接触角(WCA)表征复合超滤膜的亲水性.在0.02 MPa恒压下死端过滤油/水乳液,测试复合超滤膜的过滤性能.结果表明,最优条件下制备的复合超滤膜死端过滤油/水乳液的通量为(42.50±4.78)L/(m~2·h),截留率达到(95.72±0.33)%;循环使用5次后,依然具有较好的过滤性能,常压下死端过滤复合超滤膜的纯水通量为(3469±28)L/(m~2·h).     

PP/PMIA@PVDF-HFP纳米纤维复合滤材的制备及性能

随着空气污染的日益严重,高效低阻空气过滤材料的开发成为研究热点.为了提高聚丙烯(PP)熔喷过滤材料的过滤性能,本文以PP熔喷过滤材料为基材,聚偏氟乙烯-六氟丙烯(PVDF-HFP)为皮层,聚间苯二甲酰间苯二胺(PMIA)为芯层,采用同轴静电纺丝技术制备了具有高效低阻特性的PP/PMIA@PVDF-HFP纳米纤维复合滤材,研究了纺丝工艺和热处理等对滤材形貌、孔径、透气性和过滤性能的影响.在高温作用下,耐高温性能优异的芯层组分PMIA可以保持原有形态,而低熔点的皮层组分PVDF-HFP将会熔融,进而将纳米纤维粘结在一起.因此,通过热处理的方式可以实现纳米纤维膜孔结构的调控,并提高复合纤维滤材对空气中微小颗粒物的拦截能力.结果表明,当静电纺丝时间为60 min时,热处理后PP/PMIA@PVDF-HFP纳米纤维复合滤材孔隙率稳定在约75%,平均孔径为2.58μm,透气率为132.74 mm/s;对粒径<2.5μm的固体颗粒物(PM2.5)的过滤效率可达97.67%,过滤阻力仅为45.1 Pa,综合性能较优,且在不同风速、不同颗粒物浓度和长时间使用等条件下仍能保持优异的过滤性能.     

基于静电纺丝技术的PET/PVA复合超滤膜制备条件的探索

采用多喷头静电纺丝技术制备了复合超滤膜,该复合超滤膜是以聚对苯二甲酸乙二酯(PET)无纺布为支撑层,PET/PVA复合纳米纤维膜为分离层,再用丙酮和水的混合溶剂处理得到致密分离层.采用扫描电镜法(SEM)、红外光谱法(FTIR)对复合膜表面进行表征,测试了复合超滤膜的抗水解性能.SEM结果表明,复合膜表面的PET纳米纤维的直径为960 nm,PVA纳米纤维的直径为320 nm,用不同比例的混合溶剂对复合超滤膜进行处理会产生不同的表面形貌,最佳的比例是w(丙酮)/w(水)=30/70.抗水解性能实验结果显示比较适宜的交联剂加入量为2 wt%,用该含量对复合膜进行交联,复合膜具有较好的抗水解性能,其中重量损失率为2.12%,溶胀度为3.62%.红外光谱分析表明,交联处理后,复合膜表面的—OH量大大减少,耐水性能提高,交联前后膜表面在—C O和C—O—C处的吸收峰有很大的区别.     

PVA/DTC纳米纤维的制备及对铅离子的吸附行为

通过高压静电纺丝技术制备了聚乙烯醇/聚乙烯亚胺(PVA/PEI)纳米纤维膜, 对纤维膜进行功能化使其转化为对重金属离子具有高络合能力的聚乙烯醇/二硫代氨基甲酸盐功能化聚乙烯亚胺(PVA/DTC)纳米纤维膜. 研究了PVA/PEI纳米纤维膜的交联和功能化以及PVA/DTC纤维膜对铅离子的吸附行为. 结果表明, 高压静电纺丝法可制备出纤维直径分布均匀、 形貌良好的纳米纤维膜, 且交联、 功能化后仍能保持蓬松纳米纤维状的网状结构. PVA/DTC纳米纤维膜对铅离子吸附速率快, 吸附量容量高, 且具有良好的再生吸附能力, 是一种潜在的重金属离子高效吸附材料.     

增强复合静电纺纳米纤维膜

静电纺丝纳米纤维膜具有孔隙率高、孔径小、透气性好等优良性能。但由于纤维太细,且纤维间没有有效的粘结,其强度较低,严重限制了它的应用。本文采用高/低熔点热熔性的两种高聚物进行混合静电纺丝,制备了聚丙烯腈/聚偏氟乙烯-六氟丙烯(PAN/PVDF-HFP)、聚偏氟乙烯/聚偏氟乙烯-六氟丙烯(PVDF/PVDF-HFP)复合纳米纤维膜,并通过110℃、3MPa、5min的热压后处理,使PVDF-HFP部分熔融,制得具有点粘结的增强复合纳米纤维膜。测试结果显示,较处理前,增强PAN/PVDF-HFP、PVDF/PVDF-HFP复合纳米纤维膜的拉伸断裂强度分别提高了923.1%和665.7%,达到17.8MPa和26.9MPa,且同时保留了优良的孔隙率与透气性能。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

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.     

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%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.