Influences of the locations of monomer and initiator in the seeded polymerization systems on the morphologies of micron-sized monodispersed composite polymer particles

Three kinds of micron-sized monodispersed polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) composite particles (PS/BMA=2/1, wt. ratio) were produced by two kinds of seeded polymerizations ofn-butyl methacrylate (BMA) in the presence of about 2 m-sized monodispersed PS particles, and their morphologies were examined. One was produced by a seeded dispersion polymerization where almost monomers and initiators exist in an ethanol/water (1/1, w/w) medium. The others two were produced by seeded polymerizations utilizing the dynamic swelling method, where almost monomers exist in the PS seed particles, with 2,2-azobisisobutyronitrile initiator in the monomer-swollen particles and with 2,2-azobis [2-(2-imidazolin-2-yl)propane] initiator in an ethanol/water (1/5, w/w) medium. In the former polymerization, the produced composite particles had a core-shell structure consisting of a PS-core and a PBMA-shell, whereas in the latter two polymerizations, they had a POO (Polymeric Oil-in-Oil) structure consisting of a PS-matrix and many PBMA-domains, regardless of the location of initiator in the systems. From these results, it is concluded that the location of BMA monomer in the seeded polymerization systems with micron-sized monodispersed PS seed particles greatly affects the morphologies of produced PS/PBMA composite particles.Part CLI of the series Studies on Suspension and Emulsion     

Studies about the dispersion process and structure of impregnated CuO/ZrO2 systems

The dispersion process and structure of impregnated CuO/ZrO₂ systems were studied by x‐ray diffraction (XRD) and extended x‐ray absorption fine structure (EXAFS). The results showed that, after being calcined at 773 K, monolayer dispersed cupric nitrate decomposed into monolayer dispersed cupric oxide on zirconia's surface. The dispersion threshold of CuO was related to its precursor, cupric nitrate. The surface‐dispersed Cu nearest coordination structure changed into about five equally long Cu–O bonds. Copyright © 2003 John Wiley & Sons, Ltd.     

基质固相分散－高效液相色谱法测定玉米中痕量呋喃丹

本文研究了应用基质固相分散（ＭＳＰＤ）－高效液相色谱法测定玉米中痕量呋喃丹残留物的新方法，并讨论了应用ＭＳＰＤ技术进行前处理与传统残留分析的区别。本实验首次将ＭＳＰＤ技术用于玉米中呋喃丹残留物的高效液相色谱分析，并对定量检测条件作了详细的研究。     

Nb2O5/TiO2催化剂表面铌氧物种的分散状态和催化性能

用X射线粉末衍射(XRO)、拉曼光谱(LRS)、Hammett指示剂和微反测试等方法考察了负载型Nb2O5/TiO2催化剂表面铌氧(NbOx)物种的分散状态、表面酸性和催化异丁烯(IB)与异丁醛(IBA)缩合生成2，5-二甲基．2，4．己二烯(DMHD)反应的催化性能．实验测得Nb2O5在TiO2表面的分散容量为0．94mmol／100m^2TiO2，与“嵌入模型”理论计算值相近．当负载量低于分散容量的1／3时，Nb2O5主要以孤立的NbOx物种通过Nb—O—Ti链与载体表面相连，这种孤立的NbOx物种酸性很弱，催化活性很低．随负载量的增加，孤立的NbOx物种通过Nb—O—Nb键连接聚合，表面酸性增强，IB与IBA缩合生成DMHD的转化数(TON)增加．当Nb2O5负载量超过分散容量时，表面NbOx物种主要是通过Nb—O—Nb化学键相连形成多层的Nb2O5虽然催化剂的强酸中心数量有所增加，但NbOx物种表面利用率下降，催化活性增加幅度趋缓．     

Distinction between stepwise and concerted mechanisms in reductive cleavage reactions—use of voltammetric current function in the analysis of non-linear kinetic laws

A systematic way of distinguishing stepwise and concerted mechanisms in reductive cleavage reactions has been formulated involving current function analysis of the voltammetric data. The electrochemical reductive cleavage of the carbon-iodine bond in 1,3-dichloro-2-iodobenzene has been analyzed from a mechanistic point of view to illustrate the methodology. 1,3-Dichloro-2-iodobenzene undergoes an initial stepwise electron transfer obeying quadratic activation-driving force relationship. The current function analysis yields the reorganization energy for the reduction of 1,3-dichloro-2-iodobenzene and the results have been verified independently using convolution potential sweep voltammetry.     

载钯硅磷酸铝分子筛催化剂的一步合成及其结构

将不同形式的钯源加入到硅磷酸铝子筛反应物凝胶中，用一步法直接合成了ＰｄＳＡＰＯ－５双功能催化剂，并对其进行了改性和表征。结果表明，ＳＡＰＯ－５可在较宽的ＰＨ值范围内合成，当钯以Ｈ２ＰｄＣｌ４加入时，并不影响ＳＡＰＯ－５分子筛的形成，溶液中的钯可完全均匀地分布在分子筛孔道中，而硅的分布状态略有改变     

Facile approach to obtain individual‐nanotube dispersion at high loading in carbon nanotubes/polyimide composites

A big challenge in making a composite lies in achieving individual‐nanotube dispersion of carbon nanotubes (CNTs) in a polymer matrix, without aggregation and entanglement and excellent interfacial adhesion between the CNTs and the polymers matrix. In this communication, using polyethylene glycol‐200, we successfully prepared CNT‐reinforced polyimide composites that exhibit individual‐nanotube dispertion in the matrix at high‐loading CNT's. The content of CNTs in a composite can reach 43 wt%. Copyright © 2007 John Wiley & Sons, Ltd.     

Computer-aided optimization of stepwise gradient profiles in thin-layer chromatography

Summary Two mixtures, one containing model coloured solutes and the other glycosides from the Digitalis species were separated by stepwise gradient thin-layer chromatography, the first in the system silica-toluene + ethyl acetate, the second in the system silica-ethyl acetate + methanol. The optimal gradient programs (i.e., for which maximal spread of spots along the plate is observed) were determined using a computer program reported in an earlier paper. Good separation and satisfactory agreement of predicted and experimental R_F values were obtained; the non-aqueous system for the separation of lanatosides permits considerable shortening of elution time owing to the lower viscosity of ethyl acetate-methanol mixtures.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.     

DYNAMIC RHEOLOGICAL BEHAVIOR OF POLYPROPYLENE FILLED WITH ULTRA-FINE POWDERED RUBBER PARTICLES

Dynamic rheological characteristics of polypropylene (PP) filled with ultra-fine full-vulcanized powdered rubber (UFPR) composed of styrene-butadiene copolymer were studied through dynamic rheological measurements on an Advanced Rheometric Expansion System (ARES). A specific viscoelastic phenomenon, i.e. “the second plateau“, appeared at low frequencies, and exhibits a certain dependence on the amount of rubber particles and the dispersion state in the matrix. This phenomenon is attributed to the formation of aggregation structure of rubber particles. The analyses of Cole-Cole diagrams of the dynamic viscoelastic functions suggest that the heterogeneity of the composites is enhanced on increasing both particle content and temperature.