4-苯乙炔基苯胺封端聚酰亚胺树脂的合成与性能研究

使用4-苯乙炔基苯胺(4-PEA)作为反应性封端剂,和3,3′,4,4′-二苯醚四酸二酐(ODPA),3,3′,4,4′-联苯四酸二酐(BPDA),1,4-双(4′-氨基-2′-三氟甲基苯氧基)苯(BTPB)和3,4′-二氨基二苯醚(3,4-′ODA)反应合成了系列4-苯乙炔基苯基封端的聚酰亚胺低聚物,对低聚物的化学结构、热性能和熔体粘度以及固化后树脂的热性能等进行了研究.实验结果表明,低聚物均具有一定的结晶性,含有ODPA的聚酰亚胺低聚物较之含有BPDA的低聚物具有更低的熔体粘度,且出现最低熔体粘度的温度更低;固化后的树脂表现出良好的热性能,含有BPDA的树脂具有更高的玻璃化转变温度;系列低聚物中二胺单体的比例对于低聚物的熔体粘度和固化后树脂的热稳定性有一定影响.     

丙烯酸水溶液聚合法制备PTFE/PAA/Nafion膜及其性能

采用廉价的多孔聚四氟乙烯(PTFE)膜作为基底, 用少量的Nafion与PTFE膜复合可制备低成本的质子膜. 但疏水性的PTFE膜与亲水性的Nafion膜结合性不佳. 基于此, 本文对疏水性的PTFE膜材料表面进行设计, 先采用丙烯酸对疏水性的PTFE膜表面进行亲水性改性, 再喷涂亲水性Nafion膜, 完成低成本PTFE/PAA/Nafion膜的制备. 实验结果表明, 改性前的PTFE膜材料水接触角为150°, 改性后的膜接触角变为55.6°, 亲水性大幅上升, 膜的机械强度和尺寸稳定性(断裂强度为25.2 MPa, 80 ℃下的溶胀率为11.9%)均优于Nafion117膜, 而 Nafion用量则节省了60%. PTFE/PAA/Nafion膜具有高质子导通率(80 ℃下达到131.9 mS/cm), 接近于Nafion117膜, 最大功率密度可以达到404.2 mW/cm².     

金属有机框架材料的研究进展

金属有机框架(metal-organic frameworks,MOFs)材料是一类由有机配体与金属中心经过自组装形成的具有可调节孔径的材料。与传统无机多孔材料相比,MOFs材料具有更大的比表面积,更高的孔隙率,结构及功能更加多样,因而已经被广泛应用于气体吸附与分离、传感器、药物缓释、催化反应等领域中。新兴材料的出现极大地促进了各个学科间的相互发展,本文综述了近年来MOFs材料的研究发展,包括MOFs材料自身的特点、国内外发展现状、应用领域以及复合MOFs材料的研究热点,并对今后的发展进行了展望。     

4-苯乙炔苯酐封端聚酰亚胺树脂的合成与性能研究

使用3,3′,4,4′-二苯醚四酸二酐(ODPA)、3,3′,4,4′-联苯四酸二酐(BPDA)、1,3-双(4-氨基苯氧基)苯(1,3,4-APB)、3,4′-二氨基二苯醚(3,4′-ODA)和反应性封端剂4-苯乙炔苯酐(4-PEPA)合成了设计分子量为5000的系列苯乙炔基封端的聚酰亚胺低聚物,并使用XRD、DSC、TGA、FT-IR、DMA和流变仪等对低聚物的化学结构、热性能和熔体性能,固化后树脂的热性能和力学性能进行了测试.研究结果表明基于ODPA的低聚物具有低的熔体粘度和良好的熔体粘度稳定性,固化后的树脂具有很高的热失重温度,较高的玻璃化转变温度以及良好的力学性能尤其是高的断裂伸长率(>10%);基于BPDA的低聚物具有一定的结晶性,其结晶熔融温度与苯乙炔基固化交联温度相近,影响了材料的成型工艺性能.     

Biotin-avidin mediated competitive enzyme-linked immunosorbent assay to detect residues of tetracyclines in milk

Tetracycline (TC) antibiotics are widely used for prevention and control of disease because they inhibit the growth of bacteria. However, the presence of TC antibiotics residues in food causes harmful effects on consumer's health such as allergic reactions, liver damage and gastrointestinal disturbance, so that many countries have set MRLs (maximum residue levels). Therefore, it is necessary to detect tetracycline residues, to develop suitable analytical techniques to be used as routine screens and field detection.A new approach to the biotin-avidin mediated competitive ELISA is developed to determine tetracycline residues in milk. After optimization, the LOD and LOQ were 1.0 × 10^− 10 M (0.048 μg/L) and 1.0 × 10^− 9 M, respectively, and the working range from 3.16 × 10^− 10 M to 3.16 × 10^− 7 M toward TC in milk. No cross-reactivity was observed with the structurally similar compounds; chlortetracycline (13.7%), oxytetracycline (10%) and doxytetracycline (< 1%). Additionally percent recoveries of TC spiked in milk were quite satisfactory (∼ 90%). Comparing our results obtained in this work with others, it shows with the capability to detect TC ranging in MRLs (100 μg/L in milk) sufficiently with highly sensitivity in milk, and with simple pre-treatment. In addition, this method can apply to developing useful ELISA test kit for determination of TCs in milk.     

Evaluation of stage acoustics in Seoul Arts Center Concert Hall by measuring stage support

Stage acoustics is an important characteristic for concert halls, both for the acoustic quality on stage and for the audience. However, relatively little research has been conducted into the question. This study was based on the investigation of an actual concert hall stage, that of the Seoul Arts Center Concert Hall in Korea. The stage acoustics was evaluated in the actual hall, and with two models: a 1:25 scale model and a computer model. The study was based on the stage support parameter ST1 proposed by Gade as a measure of support for individual performers [Acustica 65, 193-203 (1989)]. The variation of support was measured on the empty stage of the actual hall and in the two models. The effect of musicians on stage, the effect of moving the orchestra, the effect of ceiling height and of stage-wall profile were also investigated. Conclusions are drawn both relating to the Seoul Concert Hall stage and stages in general.     

电子束蒸发沉积Ir膜真空紫外反射特性

Ir是一种重要的真空紫外反射材料,在太阳物理、宇宙物理、生命科学、大气物理、同步辐射等方面有着十分重要的应用.对电子束蒸发沉积Ir膜在真空紫外波段的反射特性进行了系统的理论和实验研究.根据吸收材料基底上单层金属膜数学计算模型,对不同基片上各种厚度的Ir膜真空紫外反射率进行了优化计算.根据计算和前期实验结果,采用电子束蒸发方法,在石英、K9玻璃基片上沉积了不同厚度的Ir膜,在入射波长120 nm处获得了近30%正入射反射率,对应的Ir膜厚度为12 nm.过厚或过薄均不利于Ir膜反射率的提高.经退火处理后,Ir膜中张应力有所释放但并未消除,同时晶粒平均尺寸显著增大,反射率下降.     

Mo/Si aperiodic multilayer broadband reflective mirror for 12.5-28.5-nm wavelength range

Aperiodic molybdenum/silicon (Mo/Si) multilayer designed as a broadband reflective mirror with mean reflectivity of 10% over a wide wavelength range of 12.5-28.5 nm at incidence angle of 5° is developed using a numerical optimized method. The multilayer is prepared using direct current magnetron sputtering technology. The reflectivity is measured using synchrotron radiation. The measured mean reflectivity is 7.0% in the design wavelength range of 12.5-28.5 nm. This multilayer broadband reflective mirror can be used in extreme ultraviolet measurements and will greatly simplify the experimental arrangements.     

Practical Synthesis of New β‐Diketone‐Connected Bipyridine and Its Conversion to Pyrazole‐Centered Bipyridine Ligand

Two new polydentate ligands, 1‐(6‐hydroxymethyl‐2‐pyridyl)‐3‐(2‐pyridyl)‐propane‐1,3‐dione (6) and 1,3‐bis(6‐hydroxymethyl‐2‐pyridyl)‐propane‐1, 3‐dione (8), have been synthesized starting from 2,6‐pyridinedicarboxylic acid by conventional esterification, reduction, and condensation reactions. They were further converted to two new polydentate ligands, 3‐(6‐hydroxymethyl‐2‐pyridyl)‐5‐(2‐pyridyl)‐1H‐pyrazole (7) and 3,5‐bis(6‐hydroxymethyl‐2‐pyridyl)‐1H‐pyrazole (9), by reaction with hydrazine hydrate. These four compounds were characterized by proton nuclear magnetic resonance (¹H NMR), electrospray ionization‐mass spectrum (ESI‐MS), infrared spectrum (IR), and elemental analyses. The structure of 9 was also determined by X‐ray diffraction.