Synthesis and characterization of fluoro-substituted β-enaminoketonato titanium complexes and their catalytic behavior of regioselective ethylene/cyclopentadiene copolymerization

The ethylene/cyclopentadiene (CPD) copolymerization behavior by using fluoro-substituted bis(β-enaminoketonato) titanium complexes [FC₆H₄NC(CH₃)CHCO(CF₃)]₂TiCl₂ (1a–1c) has been investigated in detail. Upon utilizing MMAO as a cocatalyst, complexes 1a–1c exhibit high catalytic activities, affording the copolymers with high molecular weight and unimodal molecular weight distribution. Compared with non-substituted complex [C₆H₅NC(CH₃)CHCO(CF₃)]₂TiCl₂ (1), complexes 1a–1c can produce the copolymers with CPD incorporation adjusted in a wide range due to the enhancement of electrophilicity of metal center caused by introducing electron-withdrawing groups. Especially complex 1c bearing fluorine at the para-position of N-aryl moiety provides the highest CPD incorporation, which is nearly two times (18.5 mol%) higher than the non-substituted complex 1 (8.9 mol%) under the same conditions. The highest CPD incorporation up to 24.6 mol% can be easily achieved using this complex. ¹H- and ¹³C-NMR spectra demonstrate that these fluoro-substituted complexes possess regioselective nature with exclusive 1,2-insertion fashion, and alternating ethylene-CPD sequence can be detected at high CPD incorporation.     

SYNDIOSPECIFIC POLYMERIZATION OF STYRENE WITH MULTI-NUCLEAR TITANIUM COMPLEXES

Two multi-nuclear titanium complexes [Ti(η5-Cp*)Cl(μ-O)]3 (1) and [(η5-Cp*TiCl)(μ-O)2(η5-Cp*Ti)2(μ-O)(μ-O)2]2Ti (Cp* = C5Me5) (2) have been investigated as the precatalysts for syndiospecific polymerization of styrene. In the presence of modified methylaluminoxane (MMAO) as a cocatalyst, complexes 1 and 2 display much higher catalytic activities towards styrene polymerization, and produce the higher molecular weight polystyrenes with higher syndiotacticities and melting temperatures (Tm) than the mother complex Cp*TiCl3 does when the polymerization temperature is above 70℃and the Al/Ti molar ratio is in the low range especially.     

关于连续映射半群拓扑熵的一点注记

本文研究了度量空间中连续映射构成半群的拓扑熵.利用Patr′ao~([8])的方法,给出了度量空间中两种有限个连续映射构成的半群的拓扑d-熵的定义,比较了两种拓扑d-熵的大小.证明了局部紧致可分度量空间上有限个真映射构成的半群的拓扑d-熵和它的一点紧化空间上对应的拓扑熵相等.上面结果推广了Patr′ao的相应结论.     

Introduction of Constrained Cyclic Skeleton into β-Enaminoketonato Vanadium Complexes: A Strategy for Stabilization of Active Centre of Vanadium Catalyst for Ethylene Polymerization

Several novel mono( ?-enaminoketonato) vanadium complexes bearing constrained cyclic skeleton, including[(C6H5)C6H3C(O) = C(CH2)nCH = N ― Ar]VCl2(THF)2(V3a: n = 1, Ar = C6H5; V4a: n = 2, Ar = C6H5; V4b: n = 2, Ar =C6F5; V4c: n = 2, Ar =(C3H7)2C6H3; V5a: n = 3, Ar = C6H5), were synthesized and their structure and properties were characterized. The structures of V4 c and V5 a in solid-state were further confirmed by X-ray crystallographic analysis.Density functional theory(DFT) results indicated that these complexes showed enhanced steric hindrance around the metal center as compared with the acyclic analogues. Upon activation with Et2 Al Cl and in the presence of ethyl trichloroacetate as a reactivator, all of the complexes exhibited high catalytic activities(107 g PE/(mol V·h)) toward ethylene polymerization, and the obtained polymers exhibited unimodal distributions(Mw/Mn = 2.0-2.3) even produced at elevated temperatures(70-100 °C) and prolonged reaction time. When MAO was employed as a cocatalyst, they only showed moderate catalytic activities(105 g PE/(mol V·h)), but the resulting polymers had higher molecular weights(168-241 kg/mol). These vanadium complexes with cyclic skeleton also showed high catalytic activities toward ethylene/norbornene copolymerization. The produced copolymers displayed approximate alternating structure at high in-feed concentration of norbornene. The catalytic capabilities of these complexes could be tuned conveniently by varying ligand structure. Furthermore, the cyclic voltammetry results also proved that these complexes exhibited better redox stabilities than the complexes bearing linear skeleton.     

一种小型无人倾转旋翼机全包线飞行的参数估计方法(英文)

小型无人倾转旋翼机的核心是飞行控制系统与捷联惯性导航系统(SINS)。针对小型无人倾转旋翼机的不同飞行模式设计了一套线性、计算效率高的捷联导航算法,为控制系统提供真实可靠的反馈参数。在直升机悬停与小速度飞行模式,利用加速度计与磁强计的输出计算测量姿态角并根据角度与角速率的关系设计低阶线性姿态估计算法,递推解算出MEMS陀螺的漂移特性,并实时补偿测量的角速率。在倾转与飞机飞行模式飞行器具有持续加速与高速的飞行特性,利用磁强计解算当前航向并引入GPS的速度与位置参数,设计了基于误差的线性Kalman滤波器,提高持续加速飞行状态的姿态估计精度。数值仿真表明在全包线飞行过程中设计的捷联导航算法具有良好的测量精度,并利用小型无人倾转旋翼机的飞行试验,验证了算法的估计性能与可靠性。     

配合物[Ni(IDB)~2][C~6H~4(OH)COO]·ClO~4· CH~3CH~2OH·H~2O的合成、晶体 结构及催化尿素水解 活性的研究

报道三齿配体N,N-二(2-苯并咪唑甲基)亚胺(IDB)及单核镍(Ⅱ)配合物[Ni(IDB)~2][C~6H~4(OH)COO]·ClO~4·CH~3CH~2OH·H~2O的合成、晶体结构和催化尿素水解活性。该配合物为三斜晶系,P1空间群,a=1.1010(2)nm,b=1.3800(3)nm,c=1.5550(3)nm,α=100.75(3)°,β=102.97(3)°,γ=107.56(3)°,V=2.1113(7)nm^3,Z=2,F(000)=952,D~c=1.438g/cm^3,M~r=914.01,μ=0.591mm^-^1。最终因子R[I>2σ(I)]:R~1=0.0591,ωR~2=0.1325;R(全部数据)：R~1=0.1302,ωR~2=0.1572。结构分析表明,镍(Ⅱ)分别与两个配体中的四个苯并咪唑氮和两个亚胺基氮配位形成畸变的八面体构型。用气相色谱仪测定配合物催化尿素水解的活性。     

水溶性荧光聚合物用于测定聚赖氨酸

合成了一种水溶性荧光聚合物聚[5-甲氧基-2-(3-磺酰化丙氧基)-1,4-苯撑乙烯](MPS-PPV),对该聚合物进行了元素分析、红外光谱及透射电子显微镜表征.实验结果表明,聚赖氨酸(PLL)对该聚合物荧光具有明显的猝灭作用,据此建立了一种快速灵敏测定聚赖氨酸的新方法,检出限为5.0×10^-10mol/L.探讨了聚赖氨酸猝灭MPS-PPV荧光的机理.     

ESR膜及在POLAR探测器中的应用

基于巨双折射光学的增强型镜面反射膜(ESR)具有高分子多层膜结构。在10~80°反射角范围内,利用623.8nm,532nm,441.6nm和413.1nm激光对ESR的反射率进行了测量,结果显示,在整个范围内有较均匀的反射率,平均反射率大于95%,平均透过率小于0.5%。XRD分析显示ESR在大尺度范围内有良好的晶化结构。在γ射线极化仪POLAR应用中,ESR作为BC448塑料闪烁体探测器反射层比用黑漆反射层的光子收集效率提高了近10倍。     

Ambient temperature living radical copolymerization of styrene and methyl methacrylate with sodium hypophosphite as reducing agent

A facile, safe and economical reducing agent, sodium hypophosphite(Na H2PO2·H2O), has been successfully employed for ambient temperature living radical copolymerization of styrene(St) and methyl methacrylate(MMA). Such effective reducing agent significantly improved the reactivity of low reactive St monomers during the copolymerization, where the reactivity ratios of St and MMA were determined to be 0.50 and 0.36 by Finemann-Ross method. Thus the copolymerizations proceeded fast and showed typical living/controlled features, as evidenced by pseudo first-order kinetics of polymerization, linear increase in molecular weight versus monomer conversion, and low polydispersity index values. Effects of the concentration of reducing agent and the monomer feed ratio on the copolymerization were investigated in detail. Furthermore, gel permeation chromatography and 1H-NMR analyses as well as chain extension experiments confirmed the high chain-end functionality of the resultant copolymer.     

CaO对煤中砷挥发性的抑制作用

在一定条件下CaO与As化合生成稳定的Ca3 (AsO4 ) 2 。模拟固定床燃烧试验 ,815℃下 ,CaO对煤中砷挥发性的抑制率范围在 3 0 5 %～ 37 35 % ,平均为 15 31% ,抑制效果明显。又进行了循环流化床燃烧试验 ,加入CaO后 ,砷在不同粒级流化床灰中的配置明显发生变化。细粒飞灰中砷含量明显降低 ,<0 0 30 8mm飞灰中砷含量从 172 8mg kg-1降至 17 6 7mg kg-1。烟道灰中砷含量降低 4～ 5 4倍以上。说明在煤燃烧过程中 ,一定温度条件下 ,CaO不仅可以固硫 ,而且对砷的挥发性也有明显的抑制作用。