聚丙烯酰胺/醋酸铬与聚丙烯酰胺/酚醛胶态分散凝胶的纳米颗粒自组织分形结构

采用原子力显微镜 ,分别对无机交联体系聚丙烯酰胺 Cr3+ 和有机交联体系聚丙烯酰胺 酚醛胶态分散凝胶的微观结构进行了显微图像分析 .发现无论是在有机还是无机交联体系中 ,也无论聚丙烯酰胺和交联剂浓度如何变化 ,在微米尺度上最终形成的都是具有自相似性的树枝状分形图像 ,在更小尺度上则发现单个小树杈分形体都是由纳米级的颗粒紧密堆积而成 .在所研究的胶态分散凝胶体系中 ,树枝状分形结构的形成及其具体的形态取决于聚丙烯酰胺的浓度 ,而交联剂的有无及其多少只对树枝状凝胶分形的几何形态产生一定影响 .实验结果还表明纳米级 (≤ 10 0nm)的胶体颗粒构成的分形结构的凝胶其弹性模量G′比微米级的高出一个数量级 .且粒子尺度越小 ,则凝胶的力学稳定性越强     

Study of the Complexation Behavior of Calixarene with Transition Metal Cations by UV—vis and Fluorescent Spectra

A new fluorescent compound based on calix[4] arene skeleton was synthesized.Its complexation ability with transition metal ions,such as Fe^3 ,Co^2 ,Ni^2 ,Cu^2 ,Zn^2 and Ag^ ,Was investigated by UV-vis and fluorescent spectra.     

Strong influences of cocatalyst on ethylene/propylene copolymerization with a MgCl2/SiO2/TiCl4/diester type Ziegler-Natta catalyst

Using triethylaluminum (TEA), triisobutylaluminum (TIBA) or TEA/TIBA mixtures of molar ratio 75/25, 50/50 and 25/75 as the cocatalyst, five different ethylene-propylene copolymer samples were synthesized by a MgCl₂/SiO₂/TiCl₄/diester type Ziegler-Natta catalyst in a slurry polymerization process. The synthesized copolymers are strongly heterogeneous in chain structure and were fractionated into part of nearly random copolymer and part of segmented copolymer. Both polymerization activity and copolymer structure were found to be markedly changed when the cocatalyst was changed from TEA to TEA/TIBA mixtures or pure TIBA. As the content of TEA in cocatalyst increases, yield of the random part of product increases and the yield of the crystalline segmented copolymer part decreases. There is also a decrease in ethylene content of the whole product with increasing TEA amount. Copolymerization behaviors of the TEA/TIBA mixture activated catalysis systems are not simple superposition of those activated by pure TEA and TIBA. When a 50/50 TEA/TIBA mixture was used as cocatalyst, the copolymerization activity became the highest, and yields of both the random copolymer part and the segmented copolymer part are close to the highest level. On the other hand, both parts of the copolymer produced with a 50/50 TEA/TIBA mixture are relatively more blocky than the products of TEA or TIBA systems, and difference in ethylene content between the random part and the segmented part was the smallest. The segmented copolymer part of three typical samples was further fractionated by temperature-gradient extraction fractionation into fractions of different ethylene content and sequence distribution. Changing TEA content in the cocatalyst exerted strong influences also on the fraction distribution of the segmented part of copolymer.     

Determination of inosine 5′-monophosphate and guanosine 5′-monophosphate in pig feed by capillary zone electrophoresis

A capillary zone clectrophoresis method was developed for the determination of IMP and GIMP, commonly used as flavor enhancers in poultry feed, in a real sample of complex composition. A baseline separation of inosine 5′-monophosphate and guanosine 5′-monophosphate was achieved within 10 min and the other components in the sample did not interfere with the separation. Quantitative results obtained from pig feed samples are presented. The separation conditions and experimental reproducibility are also discussed.     

铬（Ⅲ）邻菲咯啉,8—羟基喹啉配合物／Y型分子筛的制备及苯酚催化羟化

制备了铬（Ⅲ）邻菲咯啉，８－羟基喹啉配合物／Ｙ型分子筛，利用元素分析，ＳＥＭ，ＵＶ－ＶｉｓＢＥＴ及ＸＲＤ等方法确定了分子筛选笼中金属配合物的生在及其晶体结构，考察了实验参数对苯酚转化率及产物选择性的影响。     

A New Efficient Synthesis of p-Nitrocalix[4]arene

A new efficient synthesis of p-nitrocalix[4]arene from calix[4]arene by using nitrogen dioxide is described.The compound is an useful intermediates for the introduction of other functional groups to obtain N containing substituted calix[4]arene.The reaction mechanism is briefly discussed.     

Facile synthesis of 9-（N-amino-4-fluoromethyl-3-pyrrolidinyl）-2- fluoro-6-aminopurine from trans-4-hydroxy-L-proline

A novel and simple procedure for synthesis of azanucleoside by Mitsunobu reaction between N-(p-nitrobenzyloxycarbonyl)- trans-4-hydroxy-D-proline methyl ester obtained from trans-4-hydroxy-L-proline after six-step reaction and 2-fluoro-6-azidopurine is described,and azanucleoside is fluorinated by new fluridizer 2,2-difluoro-1,3-dimethylimidazolidine (DFI).All reactions could be carded out under mild condition.     

Studies on fluorenscence resonance energy transfer between CdS nanoparticles and DOCAI dyes

The water-soluble CdS nanoparticles were synthesized in aqueous solution. A novel fluorescence resonance energy transfer (FRET) system with CdS nanoparticles as energy donors and 3,30-diethyl-oxadicarbocyanine iodide (DOCAI) dyes as energy accepter has been developed.     

Preparation of flame retardant polyamide 6 composite with melamine cyanurate nanoparticles in situ formed in extrusion process

This paper is focused on in situ preparation of melamine cyanurate (MCA) nanoparticles from reaction of melamine (MEL) and cyanuric acid (CA) and their flame retardant polyamide 6 (PA6) composite in the extrusion process through a novel reactive processing method. Fourier transform infrared (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were utilized to characterize the in situ formed MCA nanoparticles and their blends with PA6. Introduction of pentaerythritol (LTP) and water-bound plasticizer dioctyl phthalate (DPT) into the extrusion reaction system greatly inhibits the evaporation of water required for melamine and cyanuric acid reaction at high temperature (higher than 180 °C), laying a foundation for successful in situ preparation of MCA through reactive processing. XRD and FT-IR measurements indicate that under the effect of pentaerythritol, dioctyl phthalate and water, melamine really reacts with cyanuric acid to in situ form MCA in extrusion process. The reaction degree is close to 100%. A very important finding through SEM is that the in situ formed MCA particles, which were found to have aspect ratio of about 7.5, radial size in the range of 70-300 nm (mostly 70-90 nm) and crystallite size of less than 22 nm, are uniformly dispersed in the matrix PA6 at nanoscale. The in situ formed MCA nanoparticles greatly improve the flame retardancy and the mechanical properties of flame-retarded PA6 materials, and the introduced plasticizer dioctyl phthalate also ameliorates the related impact property. The obtained flame-retarded PA6 materials have good comprehensive performance with flame retardancy UL-94 V-0 rating at 1.6 and 3.2 mm thickness, tensile strength 48.0 MPa, elongation at break 106.3% and Izod notched impact strength 8.92 kJ/m². Compared with flame-retarded PA6 material with in situ formed MCA, the one prepared through conventional blending of PA6 with commercial MCA product has improved tensile strength but deteriorated impact strength and flame retardancy.