Syndiotactically enriched 1,2-selective polymerization of 1,3-butadiene initiated by iron catalysts based on a new class of donors

A series of phosphoryl (P=O) contained compounds: triethylphosphate (a), diethyl phenyl phosphate (b), ethyldiphenylphosphate (c) triarylphosphates (d and h-m), triphenylphosphine oxide (e), phenyl diphenylphosphinate (f) and diphenyl phenylphosphonate (g) have been prepared. Iron catalysts, which are generated in situ by mixing the compounds with Fe(2-EHA)(3) and (AlBu3)-Bu-i in hexane, are tested for butadiene polymerization at 50 degrees C. Phosphates donated catalysts have been, unprecedently, found to conduct extremely high syndiotactically (pentad, rrrr=46.1-94.5%) enriched 1,2-selective (1,2-structure content=56.2-94.3%) polymerization of butadiene.

Synthesis of Liquid Polybutadiene Having Desired 1,2-Vinyl Content with Co(naph)(2)-Al-2(C2H5)(3)Cl-3-P(OPh)(3) Catalyst System

Liquid polybutadiene with desirable 1,2-units content was synthesized by Co(naph)(2)-Al-2(C2H5)(3)Cl-3-P(OPh)(3) catalyst system. It was shown that liquid polybutadiene having adequate 1,2-unit content (vinvl =35%-40%) molecular weight(M-n = 700-3500), and acceptabele conversion(>= 55%) can synthesized after optimizing polymerization conditions.

以邻菲咯啉为配体的铬系催化剂制备1,2-聚丁二烯

以邻菲咯啉(简称Phen)为配体、异辛酸铬(简称Cr)-三异丁基铝(简称Al)为催化剂、己烷为溶剂合成1,2-聚丁二烯,考察了Phen和Al用量以及聚合温度对1,2-聚丁二烯微观结构及其相对分子质量的影响。结果表明,低相对分子质量聚合物是Cr和Al作用的结果,高相对分子质量聚合物是Cr、Phen和Al作用的结果;在Phen/Cr(摩尔比)为1.0、Al/Cr(摩尔比)为20、聚合温度为50℃的条件下,Cr-Phen-Al催化剂具有高活性,可得到1,2-结构摩尔分数约为50%、相对分子质量呈双峰分布、间同度为28%的聚丁二烯。

低熔点间同1,2-聚丁二烯热塑性弹性体的研究

本论文对异辛酸铁(Fe)-亚磷酸二乙酯(P)-三异丁基铝/三乙基铝(Al)催化体系进行研究, 合成熔点低于130℃的间同1,2-聚丁二烯热塑性弹性体,并且发现三异丁基铝与三乙基铝比例对聚合活性有较大的影响。放大实验合成的间同1,2-聚丁二烯熔点为126℃ ,其1,2-结构含量为84%,间同度为81%；数均分子量13万,重均分子量40万,分子量分布为3.0；300%定伸应力为14.2MPa,拉伸强度20.5MPa,扯断伸长率420%,断裂强度20.4MPa,硬度为94邵尔A,热分解温度435℃,具有良好的力学性能和热稳定性。

1,2,3,4-Alternate double cone conformational extreme in the supramolecular assemblies of p-sulfonatocalix[8]arene

Two supramolecular assemblies of p-sulfonato-calix[8]arene were stacked by some infinite 1D 'molecular capsule' chains in which the calixarenes adopt an unprecedented 1,2,3,4-alternate double cone conformation.

聚碳酸1,2-丙二酯/聚琥珀酸丁二酯/邻苯二甲酸二烯丙酯共混体系的研究

采用熔融共混的方法制备了聚碳酸1,2-丙二酯(PPC)/聚琥珀酸丁二酯(PBS)共混物和PPC/PBS/DAOP(邻苯二甲酸二烯丙酯)增塑共混物,对共混物的相容性、热性能、结晶性和物理机械性能进行了初步研究.研究结果表明PPC/PBS共混物为不相容体系,PPC对PBS的结晶度影响很小;PBS的加入提高了共混物的起始热分解温度(Td-5%),当共混物中PBS含量从10%增加到90%时,共混物的Td-5%可分别增加15℃到59℃.DAOP对PPC/PBS共混物有增塑作用,当PPC/PBS/DAOP的比例从30/70/0变化到30/70/30时,共混物玻璃化转变温度(Tg)下降了36.9℃.与PPC/PBS共混物相比,组成优化的DAOP增塑共混物PPC/PBS/DAOP(PPC/PBS/DAOP=30/70/5)的断裂伸长率和断裂能最大可提高31倍和34倍,分别达到655.1%和3.4 J/...

Why [6,6]- and 1,2-Benzal-3-N-4-O-Cyclic Phenylimidate C-60 Undergo Electrochemically Induced Retro-Addition Reactions while 1,4-Dibenzyl-2,3-Cyclic Phenylimidate C-60 Does Not? C-H center dot center dot center dot X (X = N, O) Intramolecular Interactions in Organofullerenes

The electrochemical properties of a series of structurally related fullerooxazoles, [6,6] cyclic phenylimidate C-60 (1), 1,2-benzal-3-N-4-O-cyclic phenylimidate C-60 (2), and 1,4-dibenzyl-2,3-cyclic phenylimidate C-60 (3), are described, and the spectroscopic characterizations of their anionic species are reported. The results show that compounds I and 2 undergo retro-cycloaddition reactions that lead to the formation of C-60 and C61HPh, respectively, upon two-electron-transfer reduction. However, compound 3 demonstrates much more electrochemical stability as no retro-cycloaddition reaction occurs under similar conditions. Natural bond orbital (NBO) calculations on charge distribution show there is no significant difference among the dianions of 1, 2, and 3, indicating that the electrochemical stability of 3 is unlikely to be caused by the charge distribution difference of the dianions of three compounds. Examination on the crystal structure of compound 3 reveals close contacts of the C-H group with the heteroatoms (N and O) of cyclic phenylimidate, suggesting the existence of C-H center dot center dot center dot X (X = N, O) intramolecular hydrogen bonding among the addends, which is further confirmed by NBO analysis.

Influence of isooctanol on the interfacial activity and mass transfer of ytterbium(III) using 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester as an acidic extractant

BACKGROUND: Introducing an adduct into an extractant system is an effective method of improving extraction performance. The effect of additives upon extraction is very important, especially in the case of interfacial behaviour. In most work published in the literature, there is little data on the interfacial behaviour of extractants and modifiers. As the mass transfer must pass through an interface, the influence of isooctanol on the interfacial activity and mass transfer of ytterbium(III) using 2-ethylhexylphosphonic acid mono-2-ethlhexyl ester has been investigated.RESULTS: With increasing amounts of isooctanol, the interfacial tension and surface excess (Gamma(max)) of the 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester(HEHEHP)-isooctanol system decreased, and the area of the absorbed HEHEHP molecule (Amin) increased. The interfacial activity of the HEHEHP-isooctanol system varied significantly depending on ionic strength and temperature and the mass transfer flux decreased with increasing isooctanol content.

Microstructures, mechanical properties and corrosion behavior of high-pressure die-cast Mg-4Al-0.4Mn-xPr (x=1, 2, 4, 6) alloys

Mg-4Al-0.4Mn-xPr (x = 1, 2, 4 and 6 wt.%) magnesium alloys were prepared successfully by the high-pressure die-casting technique. The microstructures, mechanical properties, corrosion behavior as well as strengthening mechanism were investigated. The die-cast alloys were mainly composed of small equiaxed dendrites and the matrix. The fine rigid skin region was related to the high cooling rate and the aggregation of alloying elements, such as Pr. With the Pr content increasing, the alpha-Mg grain sizes were reduced gradually and the amounts of the Al2Pr phase and All, Pr-3 phase which mainly concentrated along the grain boundaries were increased and the relative volume ratio of above two phases was changed. Considering the performance-price ratio, the Pr content added around 4 wt.% was suitable to obtain the optimal mechanical properties which can keep well until 200 degrees C as well as good corrosion resistance. The outstanding mechanical properties were mainly attributed to the rigid casting surface layer, grain refinement, grain boundary strengthening obtained by an amount of precipitates as well as solid solution strengthening.

Synthesis and Electrical Properties of New Solid State Electrolyte Materials Ce6-xHoxMoO15-delta(0.0 <= x <= 1.2)

Ce6-xHoxMoO15-delta(0.0 <= x <= 1.2) was synthesized by modified sol-gel method and characterized by differential X-ray diffraction(XRD), Raman, and X-ray photoelectron spectroscopy(XPS) methods. The oxide ionic conductivity of the samples was investigated by AC impedance spectroscopy. It shows that all the samples are single phase with a cubic fluorite structure. The solid solution Ce6-xHoxMoO15-delta(x=0.6) was detected to be the best conducting phase with the highest conductivity(sigma(t)=1.05x10(-2) S/cm) at 800 degrees C and the lowest activation energy(E-a=1.09 eV). These properties suggest that this kind of material has a potential application in intermediate-low temperature solid oxide fuel cells.

Thermal stability, crystallization, structure and morphology of syndiotactic 1,2-polybutadiene/organoclay nanocomposite

Syndiotactic 1,2-polybutadiene/organoclay nanocomposites were prepared and characterized by thermogravimetry analysis (TGA), X-ray diffraction (XRD), polarized optical microscopy (POM), and differential scanning calorimetry (DSC), respectively. The XRD shows that exfoliated nanocomposites are formed dominantly at lower clay concentrations (less than 2%), at higher clay contents intercalated nanocomposites dominate. At the same time, the XRD indicates that the crystal structures of sPB formed in the sPB/organoclay nanocomposites do not vary, only the relative intensity of the peaks corresponding to (0 1 0) and (2 0 0)/(1 1 0) crystal planes, respectively, varies. The DSC and POM indicate that organoclay layers can improve cooling crystallization temperature, crystallization rate and reducing the spherulite sizes of sPB. TGA shows that under argon flow the nanocomposites exhibit slight decrease of thermal stability, while under oxygen flow the resistance of oxidation and thermal stability of sPB/organoclay nanocomposites were significantly improved relative to pristine sPB. The primary and secondary crystallization for pristine sPB and sPB/organoclay (2%) nanocomposites were analyzed and compared based on different approaches.

The rheological behavior and dynamic mechanical properties of syndiotactic 1,2-polybutadiene

The rheological behavior and the dynamic mechanical properties of syndiotactic 1,2-polybutadiene (sPB) were investigated by a rotational rheometer (MCR-300) and a dynamic mechanical analyzer (DMA-242C). Rheological behavior of sPB-830, a sPB with crystalline degree of 20.1% and syndiotactic content of 65.1%, showed that storage modulus (G ') and loss modulus (G '') decreased, and the zero shear viscosity (eta(0)) decreased slightly with increasing temperature when measuring temperatures were lower than 160 degrees C. However, G ' and G '' increased at the end region of relaxation curves with increasing temperature and)10 increased with increasing temperature as the measuring temperatures were higher than 160 degrees C. Furthermore, critical crosslinked reaction temperature was detected at about 160 degrees C for sPB-830. The crosslinked reaction was not detected when test temperature was lower than 150 degrees C for measuring the dynamic mechanical properties of sample. The relationship between processing temperature and crosslinked reaction was proposed for the sPB-830 sample.

Syndiotactic 1,2-polybutadiene fibers produced by electrospinning

Syndiotactic 1,2-polybutadiene (s-PB) is a typical thermoplastic elastomer with various applications because of its high reactivity. In the past, it is difficult to form s-PB fibers with a diameter below 10 mu m because of the limitation of the conventional method such as melt spinning. Here, we report for the first time on the production of s-PB nanofibers by using a simple electrospinning method. Ultrafine s-PB fibers without beads were electrospun from s-PB solutions in dichloromethane and characterized by environmental scanning electron microscope (ESEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). At 4 wt.% concentration of s-PB, the average diameter of s-PB was about 130 nm. We found that dichloromethane was a unique suitable solvent for the electrospinning of s-PB fibers, and the structure of syndiotactic was changed through the electrospinning process.

PP／间同1,2-聚丁二烯的物理力学性能

添加不同质量分数的间同1,2-聚丁二烯(sPB)热塑性弹性体对聚丙烯(PP)共混改性,研究了共混体系的物理力学性能。PP与sPB结构相似,有良好的相容性,随着w(sPB)从0增至40%,共混体系的屈服拉伸强度、弯曲模量及耐热性有所降低;悬臂梁冲击强度增加,且常温悬臂梁冲击强度增幅较大,但低温悬臂梁冲击强度增加较少;断裂伸长率和熔体流动速率先增加后减少。

间同1,2-聚丁二烯的结构和结晶动力学研究

间同1,2-聚丁二烯(s-PB)由丁二烯用Fe(2-EHA)3/Al(i-Bu)3/DEP作催化剂,在己烷溶剂中50℃下聚合制备.用13C NMR谱方法测定的1,2-结构含量为89.3%,间同结构为86.5%;X射线测得聚合物的结晶度约为68%.非等温结晶动力学研究采用DSC方法,改进的Avrami方程可以很好地分析s-PB非等温结晶过程的主期结晶,表明其结晶过程是自成核,三维球形生长.Ozawa方程不适合分析s-PB非等温结晶动力学;Avrami和Ozawa方程结合的方法可以很好地描述s-PB非等温结晶过程,指数a为1.138,F(θ)随着结晶度的提高而增大;并计算了s-PB的结晶活化能.