Application of Et3NHCl-AlCl3 Ionic Liquid as an Initiator in Cationic Copolymerization of 1, 3-Pentadiene with Styrene

Room temperature ionic liquids (RTILs) as advanced, technological solvents can be designed to fit a particular application. They used as green “media and/or catalysts” for chemical synthesis have been extensively reviewed recently. RTILs1 not only show …     

Selective desorption and analysis of humic substances on suspended particles in river water

The elemental analysis and morphology of individual particles indicate that the dominant suspended particles in river water are kaolin covered with hydrated iron(III) oxide which strongly sorbs humic substances. Suspended particles, about 1 mg, collected from 250 ml of water by centrifugation, are treated with 0.7 ml of 0.1M sodium hydroxide to desorb humic substances. Approximately 60% of copper and 30% of lead on or in suspended particles exist as humic complexes.     

微波辐照制备无皂阳离子PMMA胶乳粒子

在微波辐照条件下 ,用偶氮二异丁基脒盐酸盐 (AIBA)引发甲基丙烯酸甲酯的均聚 ,制得窄分散的无皂阳离子胶乳粒子 .讨论了引发剂的浓度、单体的浓度、离子强度等对粒子大小、分散性和乳液稳定性的影响 .对微波辐照和水浴加热进行比较 ,发现微波辐照反应速度快、反应无恒速阶段 ,所得粒子的粒径小 ,粒子数目多 ,这为通过改变反应条件制备适宜的窄分散的胶乳粒子提供了一条途径 .     

纳米银掺杂二氧化硅复合颗粒的制备及表征

0引言金属纳米颗粒因其粒子尺寸小(1￣100nm),比表面积大,表面原子数多,表面能和表面张力随粒径的下降急剧增大而具有量子尺寸效应[1]、小尺寸效应[2]、表面效应[3]及宏观量子隧道效应[4]等,从而出现了不同于常规固体的新奇特性,如:光学性质、磁性质以及电磁学性质[5],使其在催化、信息存储及非线性光学等领域展示了广阔的应用前景[6]。虽然制备金属纳米颗粒的方法有很多[6],但是由于纳米尺寸的金属颗粒具有较高的表面能,容易发生聚集,所以如何保持其稳定性依旧是比较困难的问题。随着纳米科技的发展,人们正尝试用各种方法来解决这个问题:如…     

Metal Oxide Thin Films Containing Au Nano-Particles Prepared with Gas Diffusion Method

Au particles dispersed thin metal oxide films were prepared from precursor films containing HAuCl₄ with H₂S gas diffusion method. HAuCl₄ was uniformly dissolved in the films as promoted by hydroxypropyl cellulose (HPC). The mechanism of the Au particle formation was studied. It was found that HAuCl₄ was converted directly to Au metal particles upon contacting with H₂S gas. Au particles generated by this method were characterized with small particle size, sharp size distribution and high volume fraction in the films. The surface plasma resonance absorption of Au particles shifted to longer wavelength when TiO₂ component was introduced in the matrix.     

阳离子无皂含氟丙烯酸酯的合成与表面性能

在合成甲基丙烯酸全氟辛酰氧基乙酯(FA)基础上,用半连续法制备了无皂阳离子含氟丙烯酸酯乳液。当乳液的粒径在100~200 nm、ζ电位大于40 mV时,乳液较稳定。阳离子亲水单体甲基丙烯酰氧乙基三甲基氯化铵(DMC)在含氟丙烯酸酯中质量分数为0.10~0.18、固含量小于20%时乳液的稳定性好,且随DMC含量的增加稳定性提高;含氟丙烯酸酯乳胶膜的附着力与耐磨性好,乳胶膜的透湿率随DMC的增加而增加。随热处理温度的提高,膜表面自由能下降;经160℃热处理后膜发生了交联,表面自由能为18 mN/m,与聚四氟乙烯(PTFE)的表面能相近,DMC含量对膜表面自由能影响不大。XPS分析也表明膜表面氟含量随热处理温度的提高而增加。     

分散聚合水基聚苯胺乳胶微球制备与表征

水溶性空间稳定剂聚乙烯吡咯烷酮（PVP）存在时，采用分散聚合制备水溶性单分散的聚苯胺(PAn)乳胶粒子，采用透射电子显微镜（TEM）观察粒子形态及尺寸；利用紫外-可见吸收光谱对胶体分散体系进行表征.实验结果表明，当PAn含量较少（w< 16.78％）时， PAn-PVP复合乳胶粒子呈米粒状；当PAn含量较大（w >23.22％）时， PAn-PVP复合乳胶粒子呈球形.     

Catalysis of ring-opening and vinyl polymerizations by dicobaltoctacarbonyl

In the presence of Si? H containing cocatalysts, dicobaltoctacarbonyl has been found to very efficiently catalyze the ring-opening polymerization of cyclic ethers, especially epoxides, as well as certain vinyl monomers. The reaction conditions employed are very similar to those used in Co₂(CO)₈ catalyzed hydrogenation and hydrosilylation reactions. Detailed investigations have been carried out to elucidate the nature of the active species for this catalytic system. A cationic mechanism is proposed based on the experimental results of those investigations.     

Synthesis of nanosized TiO2/SiO2 particles using microwave processes and their photocatalytic activity on the decomposition of orange II

The nanosized titania and TiO₂/SiO₂ particles were prepared by the microwave-hydrothermal method. The effect of physical properties TTIP/TEOS ratio and calcination temperature has been investigated. The major phase of the pure TiO₂ particle is of the anatase structure, and a rutile peak was observed above 800°C. In TiO₂/SiO₂ particles, however, no significant rutile phase was observed, although the calcination temperature was 900°C. No peaks for the silica crystal phase were observed at either silica/titania ratio. The crystallite size of TiO₂/SiO₂ particles decreases as compared to pure TiO₂ at high calcination temperatures. The TiO₂/SiO₂ particles show higher activity on the photocatalytic decomposition of orange II as compared to pure TiO₂ particles.     

Cationic ring‐opening polymerization of monothiocarbonate with a norbornene group

This work deals with the cationic ring‐opening polymerization of cyclic thiocarbonates with a norbornene or norbornane moiety, that is, 5,5‐(bicyclo[2.2.1]hept‐2‐ene‐5,5‐ylidene)‐1,3‐dioxane‐2‐thione ( TC1 ) or 5,5‐(bicyclo[2.2.1]heptane‐5,5‐ylidene)‐1,3‐dioxane‐2‐thione ( TC2 ), respectively. The reaction of TC1 initiated by trifluoromethanesulfonic acid (TfOH), methyl trifluoromethanesulfonate (TfOMe), boron trifluoride etherate (BF₃OEt₂), or triethyloxonium tetrafluoroborate (Et₃OBF₄) afforded unidentified products; however, TC1 underwent cationic ring‐opening polymerization with methyl iodide as an initiator to afford polythiocarbonate because the propagating end was stabilized by the covalent‐bonding property. The polymerization of TC2 initiated by TfOH, TfOMe, BF₃OEt₂, or Et₃OBF₄ afforded polythiocarbonate with good solubility in common organic solvents and a narrow molecular weight distribution because of the absence of a double‐bond moiety. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1698–1705, 2002