Self-aggregation and phase behavior of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers in aqueous solution

The phase behavior and aggregation properties of block copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (Pluronics, poloxamers) in aqueous solution have recently attracted much attention. Both experimental and theoretical studies are reviewed, not comprehensively, but with the focus on studies, partly cooperative, partly independent, performed by groups in Uppsala (light scattering and fluorescence), Roskilde (rheology and calorimetry), Risø (SANS), Graz (x-ray and speed of sound), and Lund (theoretical model calculations).The phase behavior of these copolymers is similar in many respects to that of conventional nonionic surfactants, with the appearance of hexagonal, cubic, and lamellar liquid crystalline phases at high concentrations. In the isotropic solution phase the critical concentration for micelle formation is strongly temperature dependent, and at a given concentration the monomer to micelle transition occurs gradually over a broad temperature range, partly due to the broad size polydispersity of both the PO- and EO-blocks. For some Pluronic copolymers a transition from globular to long rod-like micelles occurs above a transition temperature, resulting in a strong and sudden increase of viscosity and viscoelasticity of the solution.Size and aggregation numbers have been determined for the globular micelles in some cases, and also the rod-like micelles have been characterized. NMR and fluorescence measurements have provided further information on the properties of the micellar core and mantle. In combination, results from different measurements on the same Pluronics material indicate that the aggregation number of the micelles increases with the temperature, whereas the hydrodynmic radius varies much less. The PEO-mantle of the micelles seems to contract with increasing temperature. The core appears to contain appreciable amounts of PEO in addition to PPO (and also some water). The segregation between core and mantle is not as distinct as in normal micelles, a conclusion which is in line with the predictions from the model calculations.     

Decomposition of hexafluoropropylene oxide in a strong IR field

Multiphoton dissociation (MPD) of hexafluoropropylene oxide (HFPO) under focused CO₂-laser radiation was studied. A high-energy channel of HFPO decomposition was revealed. The dependences of the MPD yield and the ratio between various channels of HFPO decomposition on the laser radiation frequency in the range from 967.7 to 1090.0 cm^–1, the incident radiation energy, and the initial pressure of HFPO were obtained. A considerable contribution of thermal decomposition of HFPO occurring outside of the irradiated zone to the total yield of its decomposition was established. An explanation for the pressure dependence of the yield of HFPO decomposition was suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2174–2180, November, 1995.The authors are grateful to the Russian Foundation for Basic Research for financial support of this work (Project No. 94-03-09059).     

Titanium production in a plasma reactor: A feasibility investigation

The feasibility of producing titanium metal from titanium tetrachloride in a thermal plasma under equilibrium and adiabatic expansion conditions has been theoretically investigated. Free energy minimization and adiabatic expansion calculations to simulate a nozzle expansion were used to study the practicality of production. The crucial requirements for the production of titanium powder from TiCl₄ and H₂ appear to be rapid quenching of the plasma gas at high temperature (e.g., 3700 K) and appropriate reactant concentrations. Quenching of tire plasma gas and production of titanium powder can be achieved by adiabatic expansion through a nozzle. Preliminary experimental data indicate that titanium powder of approximately 5 nm in size can be produced in an argon plasma rising a nozzle expansion approach.     

制备方法对MoO_3／ZrO_2结构的影响及MoO_3／ZrO_2固体超强酸的结构特征 Ⅰ．ZrO_2的形态与样品比表面的研究

ＸＲＤ，ＤＴＡ，比表面测定等结果表明，制备方法对ＭｏＯ３／ＺｒＯ２结构有决定性影响．仲钼酸铵浸渍仅经干燥的Ｚｒ（ＯＨ）４再经高温焙烧所得团体超强酸ＭｏＯ３／ＺｒＯ２（Ⅰ）与浸渍晶态ＺｒＯ２所得部分氧化催化剂ＭｏＯ３／ＺｒＯ２（Ⅱ）的载体形态有明显不同．（１）ＭｏＯ３／ＺｒＯ２（Ⅰ）的比表面数倍于ＭｏＯ３／ＺｒＯ２（Ⅱ）；（２）ＭｏＯ３含量增加时，ＭｏＯ３／ＺｒＯ２（Ⅰ）的比表面逐步增大至一极大值再缓缓下降，而ＭｏＯ３／ＺｒＯ２（Ⅱ）的比表面随ＭｏＯ３含量增加而单调下降；（３）在ＭｏＯ３／ＺｒＯ２（Ⅰ）中，ＺｒＯ２以介稳四方相存在，而在ＭｏＯ３／ＺｒＯ２（Ⅱ）中则是稳定的单斜相．在此基础上研究了事先引入的活性组分在载体织构形成过程中的作用，包括延迟ＺｒＯ２晶化，阻碍晶粒长大及与之相关的相变等，并讨论了ＭｏＯ３／ＺｒＯ２（Ⅰ）中ＭｏＯ３最佳含量的科学含义．     

炭担载的Mo和CoMo加氢脱硫催化剂

用仲钼酸铵和酸钴水溶液浸渍方法将ＭｏＯ３和ＣｏＯ担载在少在性炭担体上，制成Ｍｏ／Ｃ和ＣｏＭｏ／Ｃ催化剂。运用ＤＴＡ，ＸＰＳ，ＦＴ－ＬＲＳ等手段考察了ＭｎＯ３在活性炭担体表面的分散状态及Ｈ２还原能力随ＭｏＯ３含量的变化，并在中压固定床反应装置上测定了催化剂的噻吩加氢脱硫和环己烯加氢反应活性。     

Grignard试剂同6，6－二烷基富烯反应的研究

烯丙基卤化镁和环戊二烯基溴化镁同６，６－二烷基富烯分别进行富烯环外双键的加成和还原反应，生成的取代环戊二烯基负离子用（ＣｐＴｉＣｌ＿２）＿２Ｏ（Ｃｐ＝环戊二烯基）或ＴｉＣｌ４配合，合成通式为Ｃｐ（Ｃ＿５Ｈ＿１－ＣＲＲ￣１－ＣＨ＿２ＣＨ＝ＣＨ＿２）ＴｉＣｌ＿２和（Ｃ＿５Ｈ＿４ＣＨＲＲ￣１）＿２ＴｉＣｌ＿２的化合物。对烯丙基卤化镁、环戊二烯基溴化镁同富烯的反应机理进行了探讨。     

ICP－AES法测定氧化铕中14种数量稀土杂质

采用ＩＣＰ－ＡＥＳ单道扫描光谱仪详细考察了十四种被测稀土杂质元素的４７条灵敏分析线的谱线轮廓及基体Ｅｕ的背景谱线轮廓，从而选定基体干扰小，灵敏度高的分析线及扣除背景的合适位置；试验了酸度，载气流量，观测高度，射频发生器功率等对信号强度和基体干扰程度的影响，采用基体匹配法校正基体对测定的影响，建立了氧化铕中１４种稀土杂质的直接测定法。已用于出口产品的分析和标准试样的定值测定，得到了满意的结果。     

甲苯气相选择性氧化制苯甲醛 Ⅰ．V_2O_5／TiO_2－Al_2O_3催化剂研究

制备了一系列负载型Ｖ－Ｔｉ－Ａｌ－Ｏ催化剂并用于甲苯的气相选择性氧化制苯甲醛，考察了接触时间、氧浓度、Ｖ２Ｏ５负载量以及催化剂焙烧温度对反应性能的影响。用ＴＰＲ、ＸＲＤ和ＢＥＴ等测试手段，对催化剂进行了表征。研究发现，催化剂在７７３Ｋ时活化，接触时间１．２秒，氧浓度２１％时，可获得较好的反应结果，Ｖ２Ｏ５负载量为６（ｗｔ）％的催化剂，在５９３Ｋ时反应，得到了转化率２０．５％，苯甲醛产率８．３％的最好结果。     

CHARACTERIZATION OF AMPHIPHILIC AND MICROPHASE SEPARATED GRAFT COPOLYMERS Ⅱ SURFACE CHARACTERIZATION AND IN VITRO BLOOD-COMPATIBILITY ASSESSMENT OF POLYSTYRENE-GRAFT-ω-STEARYLPOLY (ETHYLENE OXIDE)*

This paper reported the research results concerning the surface characterization ofpolystyrene-graft-w-stearyl poly(ethylene oxide) (PS-g-SPEO) by means of XPS,contactangle measurement and TEM, and its in vitro blood compatibility assessment by measuringthe plasma recalcification time (RT) and partial thromboplastin time (PTT). The XPSresults demonstrated that the surface and bulk composition of the PS-g-SPEO graftcopolymers differ remarkably from each other,and that SPEO component was constantlyenriched at the copolymer/air interface. Contact angle studies indicated that the surfacewater wettability can be adjusted effectively by changing the composition of the copolymer.PS-g-SPEO graft copolymers can undergo microphase separation as clearly illustrated byTEM photographs. The relationship between the surface properties of PS-g-SPEO graftcopolymer and its blood compatibility was also discussed.     

聚苯醚磺酸锂与聚醋酸乙烯酯共混物的导电性能研究

为改善聚苯醚磺酸锂（SPPOLi）的导电性能，将聚酷酸乙烯酯（PVAc）与之共混，X-射线衍射分析表明，PVAc可降低SPPOLi凝聚结构的有序程度；发现共混后电导率有了较大提高，共混物的电导对温度的依赖关系不符合阿仑尼马斯方程；同时，共混物仍保持了单离子传导性．