Electrospinning of nylon-6,6 solutions into nanofibers: Rheology and morphology relationships

The relationship between the rheological properties of nylon-6,6 solutions and the morphology of their electrospun nanofibers was established. The viscosity of nylon-6,6 in formic acid(90%) was measured in the concentration range of 5 wt%-25 wt% using a programmable viscometer. Electrospinning of nylon-6,6 solutions was carried out under controlled parameters. The chemical structure, morphology and thermal properties of the obtained nanofibers were investigated using Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM) and differential scanning calorimetry(DSC), respectively. Entanglement concentration(ce) was found to be 15 wt% and a power law relationship between specific viscosity and solution concentration was observed with exponents of 2.0 and 3.3 for semi-dilute unentangled(c ce) and semi-dilute entangled(c ce) regimes, respectively. The diameter and uniformity of the nanofibers were found to be dependent on the viscosity. Moreover, the average diameter of electrospun nanofibers was found to be dependent on zero shear rate viscosity and normalized concentration(c/ce) in a power law relationship with exponents of 0.298 and 0.816, respectively. For nylon-6,6 solutions, the entanglement concentration(ce = 15 wt%) provides the threshold viscosity required for the formation of a stable polymeric jet during electrospinning and producing uniform beadless fibers. For concentrations less than ce, beaded fibers with some irregularities are formed. DSC analysis showed an increase in crystallinity of all electrospun samples compared to original polymer. Furthermore, Based on FTIR spectroscopy, α phase is dominant in electrospun nanofibers and minor amount of β and γ phases is also available.     

Solution Blowing of Poly（dimethylsiloxane）/Nylon 6 Nanofiber Mats for Protective Applications

A new strategy was developed to fabricate superhydrophobic nylon 6 nanofibers, in which the blend solutions of poly(dimethylsiloxane)(PDMS) prepolymer and nylon 6 was spun using an innovative solution blowing process, and then the PDMS prepolymer contianning nanofibers were cured to obtain PDMS/nylon 6 nanofiber mats. Morphology, surface composition, non-wetting property and protective performance were investigated. The results showed that the addition of PDMS prepolymer improved the spinnability of the spinning solutions, and the PDMS/nylon 6 nanofibers had smooth surfaces and diameters from 100 nm to 350 nm. The presence of PDMS effectively enhanced the hydrophobicity of the nanofiber mats, showing water contact angles of 132° to 161° for PDMS contents of 1 wt% to 3 wt%. The PDMS/nylon 6 mats also possessed excellent protective and transport properties. The results indicated the potential application of the novel nanofiber mats in protective clothing.     

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。     

石墨烯表界面化学修饰及其功能调控

石墨烯属于碳纳米材料家族中的一员,是一种单层的二维原子晶体,具有高硬度、高导热性、高载流子迁移率等诸多优良特性,被认为是新一代电子学器件的重要基础材料.近年来我们课题组利用石墨烯的这些优良特性在其表界面化学修饰及其功能调控方面开展了一系列研究工作.我们对石墨烯表界面进行了共价或非共价化学修饰,在一定程度上打开了石墨烯的带隙,并发展了具有传感功能的石墨烯器件.我们还制备了基于石墨烯的纳米电极,发展了新一代分子电子器件的普适性制备方法,实现了单分子器件的功能化.展望未来,以石墨烯为代表的碳基纳米材料将继续在纳电子器件研究领域发挥重要作用.     

石墨烯纳米孔的制备及λ-DNA穿孔初步研究

纳米孔测序是有可能实现"$1,000 Genome"目标的技术之一.近年来,研究较多的纳米孔有蛋白质纳米孔和硅基材料的固态纳米孔.蛋白孔寿命比较短,而基于硅基底的固态纳米孔深度显著超过单链DNA相邻碱基的间距,所以,无法实现DNA的单个碱基的分辨.作者用聚焦离子束先制造氮化硅基底,并在该基底上铺设石墨烯,再用聚焦电子束刻蚀石墨烯,获得直径10 nm以下的纳米孔,初步分析了DNA穿越纳米孔时产生的电信号及穿孔噪音,向单层石墨烯纳米孔测序DNA迈出了一步.     

原子荧光法测定茶叶中的硒含量

采用原子荧光法测定茶叶中的硒含量,对样品消解温度及仪器条件进行了优化。还原剂为1.0%硼氢化钾–0.5%氢氧化钾溶液,载流液为3%盐酸溶液。在优化条件下,硒的质量浓度在0~20 ng/mL范围内与荧光强度呈良好的线性关系,相关系数r=0.999,检出限为0.8 ng/mL。该法的加标回收率为88.08%~101.39%,测定结果的相对标准偏差为2.03%~4.84%(n=6)。该方法实际操作性强,准确度高,适用于日常检验工作中对批量茶叶中硒含量的测定。     

新型双荧光二氧化硅纳米颗粒的制备

本文采用改良的反相微乳液法制备得到双染料掺杂的二氧化硅荧光纳米颗粒。扫描电镜结果显示,荧光纳米颗粒呈球形,平均粒径约为90nm。利用荧光光谱及共聚焦荧光显微镜对该纳米颗粒的光学性能进行表征,结果发现其可同时发出红、绿双色荧光,这为进一步制备具有更多种荧光信号的硅纳米颗粒提供基础。同时,由于硅纳米颗粒生物相容性好,易功能化的特点,使得该新型硅纳米荧光颗粒在生物标记及生物成像的多组分分析中具有潜在的应用。     

水热法合成纳米氧化铜及其对盐酸异丙嗪的电化学传感研究

采用简单的水热法一步反应,制备了尺径均一的纳米氧化铜颗粒并构建了纳米氧化铜修饰电极。结果表明,该修饰电极对盐酸异丙嗪的电化学氧化有显著的电催化作用,研究了各种因素包括pH值、修饰剂用量、扫速以及共存离子等对电极响应的影响,优化了各项测试条件。该方法测定盐酸异丙嗪的线性范围为0.5~150μmol/L,检出限为1.3×10-7 mol/L,同时成功测定了药物中盐酸异丙嗪的含量。     

TiO_2/12-磷钨杂多酸/金复合纳米材料的制备及电化学性能

采用水热法制备TiO2纳米管(TNTs),然后以12-磷钨杂多酸(PTA)作为交联剂,运用光催化方法在TiO2纳米管表面负载金纳米颗粒(GNPs),从而得到新型复合纳米材料——TNTs-PTA-GNPs;借助傅立叶变换红外光谱仪,X射线衍射仪和透射电子显微镜分析了新型复合纳米材料的结构及形貌,并利用循环伏安法测试了其电化学性能.结果表明,GNPs均匀分布在TNTs表面,从而大幅度改善纳米材料的导电性;但复合纳米材料中无游离的金纳米颗粒.与此同时,TNTs-PTA-GNPs纳米材料具有良好的生物相容性,且可促进酶与电极之间的直接电子转移.     

纳米SiO_2/聚甲基丙烯酸甲酯复合材料的制备和力学性能

通过悬浮聚合的方法,用不同表面结构的纳米SiO2对聚甲基丙烯酸甲酯(PMMA)进行原位改性,得到纳米SiO2/聚甲基丙烯酸甲酯复合材料;利用红外光谱仪分析了复合材料的界面化学结构,利用热分析仪测定了其热稳定性,并采用冲击试验机测定了其力学性能.结果表明,不同表面结构的纳米SiO2均参与甲基丙烯酸甲酯的聚合反应,与PMMA基体之间形成化学键;而表面修饰有双键的纳米SiO2更易与甲基丙烯酸甲酯聚合,能更有效地提高PMMA的抗冲击性能.