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41.
The number of active centers (C_p)-t and k_p-t profiles of Solvay type TiCl_3 - AlR_3 (R=C_2H_5, i-C_4H_9) or Stauffer AA TiCl_3-Al (C_2H_5)_3 catalyzed 1-octene polymerization were determined by using an acetyl chloride quenching method as well as kinetic data. The results show that in the studied systems k_p decreases when C_p increases, indicating the presence of two or more types of different active centers. The C_(p~(-t)) plots of the Solvay TiCl_3-AlR_3 systems show the presence of both stable active centers and unstable centers which decay in the polymerization process. The phenomena are explained based on a model of active center plurality. The increases of C_p in the induction periods are also discussed. 相似文献
42.
43.
In this paper, highly active Ziegler-Natta catalysts of MgCl_2 supported TiCl_4 for synthesis ofpolyolefins, using di-n-butyl phthalate (DNBP) as internal donor and diphenyl dimethoxyl silane(DPDMS) as external donor, have been prepared. The conditions controlling the treatment ofsupport were studied. The interactions of various components present in the catalysts and theirinfluences on catalytic performance were investigated. It is found that by using DNBP and DPDMSas internal and external donors together the polymer products with higher isotactic index can beobtained. Plausible structure model and mechanism were proposed. 相似文献
44.
The EPR spectra of three new gadolinium complexes with noncyclic polyether Schiff bases in powder and those of these complexes in organic solvents were investigated at different temperatures. It was observed that EPR spectra of nine and four peaks of Gd(Ⅲ) complexes in polycrystalline powder and freezing samples appeared at low temperature respectively for the first time. The interpretations of these results obtained on the basis of spin Hamiltonian of s = 7/2 system are satisfactory. The correlations of EPR feature between crystal-field strength in complexes and local symmetry around Gd3+ ions were revealed. The crystal-field parameters b20 and the asymmetry parameters λ' of complexes were estimated. A series of interesting regularity and new results were obtained. 相似文献
45.
Al2O3/SnO2 co-nanoparticles were prepared with a modified sol-gel technique followed by a thermal treatment process. With these co-nanoparticles the grafted collagen-Al2O3/SnO2 nanocomposites were obtained using a supersonic dispersion method. X-ray diffraction, FT-IR analysis, transmission electron microscopy, TGA/DTA and infrared emissivity test were performed to characterize the resulting nanoparticles and nanocomposites, respectively. The Al2O3/SnO2 co-nanoparticles showed a narrow distribution of size between 20-40 nm and could be uniformly absorbed on the tri-helix scaffolds of the grafted collagen without any aggregation. The nanocomposites possessed better thermal stability and substantially lower infrared emissivity than the grafted collagen and Al2O3/SnO2 co-nanoparticles with an increase of degradation temperature from 39 to 210 ℃ and a decrease of infrared emissivity from 0.850 of the grafted collagen and 0.708 of the Al2O3/SnO2 co-nanoparticles to 0.424, which provided a potential application of the nanocomposites to areas such as photoelectronics. 相似文献
46.
本文通过对TiCl_3-Al(C_2H_5)_3聚合1-辛烯产物的双峰型分子量分布曲线用Schulz函数进行拟合、分峰处理,发现这种双峰型分布中的高分子量峰部分由一种活性中心生成,低分子量峰部分则由至少两种活性中心生成.将不同转化率时聚辛烯的分子量分布分峰拟合数据与聚合速率、活性中心数等测定数据相结合,得到了高分子量和低分子量两部分产物相应的活性中心上各自的动力学参数(增长速率常数、活性中心数、链转移常数等)及各自的聚合速率曲线,从而证实了多种活性中心的存在、它们催化特性的差异及与聚合物分子量分布增宽的关系. 相似文献
47.
A ~(13)C-NMR method is presented for a quantitative determination of the respective monomercomposition and sequence distributions in ethylene-1-octene copolymers prepared with supportedtitanium/magnesium catalyst. On the basis of the sequence distributions, the ethylene-1-octenecopolymerization mechanism was studied. It was found that the observed sequence distributions inethylene-1-octene copolymers are satisfactorily predicted by the two-site model M/M,in whichthe copolymerization proceeds according to first-order Markovian statistics at the two differentsites. 相似文献
48.
A new reactive graft copolymer, poly(tetramthylene glycol) - graft-w-propyl sodiumsulfonate-poly(ethylene glycol) (PTMG-g-PEG-CH_2CH_2CH_2SO_3~-Na~+), was synthesizedby the cationic polymerization of a-w-bifunctional PEG macromonomer (O?CH_2—PEG——CH_2 CH_2 CH_2 SO_3 Na) and THF. The obtained copolymer exhibits the expected structureas indicated by the result of characterization. Two amino acids (L-arginine, L-tyrosine)were covalently attached to the copolymer after converting the sulfonate group to sulfonylchloride. So the new reactive graft copolymer (PTMG-g-PEG-CH_2CH_2CH_2SO_3~-Na~+) isexpected to be very useful in attachment of potentially bioactive moieties to polymer viaa hydrophilic PEG spacer. 相似文献
49.
50.
研究了酪氨酸 溴酸钾 硫酸 丙酮在三邻菲啉合铁 (Ⅱ )催化下的化学振荡反应 ,对振荡的影响因素进行了研究和讨论 .运用正交实验法确立了振荡反应进行的浓度范围 ,得到一个 4 0多次振荡寿命为 6 0min的振荡波 .获得振荡的诱导期和周期与反应物浓度之间的变化趋势曲线 ,以及振荡反应在诱导期和振荡期的表观活化能分别为Ein=4 9.0kJ/mol和E =5 7.0kJ/mol.根据反应过程中的现象和实验数据 ,建立了振荡反应的模型和反应机理 ,确定 [Br-]是振荡反应自发进行的关键因素 . 相似文献