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Brian W. S. Kolthammer Debra Jean Mangold Dennis R. Gifford 《Journal of polymer science. Part A, Polymer chemistry》1992,30(6):1017-1026
The kinetic parameters have been measured for octene-1 solution polymerization at 120°C catalyzed by zirconocene with the cocatalyst methylaluminoxane. The polymerizations were performed in an attenuated total reflectance (ATR) reaction cell. The progress of the reactions were followed by observing the disappearance of octene-1 using the 910 cm?1 band measured by FT-IR spectroscopy. The dependence of the reaction rate, Rp, on catalyst concentration and cocatalyst/catalyst ratio was examined. The catalyst deactivation mechanism was studied by fitting the experimental data to mathematical models involving second-order propagation and either first or second order catalyst deactivation. Second-order catalyst deactivation provided a much better fit. The calculated deactivation rate constant, kd, is 21 (Ms)?1. This model is used to determine the propagation rate constant for Al/Zr = 4 × 103 as kp = 19.9 (M s)?1. A decrease in Al/Zr = 3 × 102 lowered the propagation rate constant, kp, to 9.6 (M s)?1 indicating that less than 50% of the initial Zr is active at this Al/Zr ratio. 相似文献
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Everta Keren Govindarajan Sundararajan 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3599-3610
The 2‐[benzyl‐(2‐hydroxy‐2‐phenylethyl)‐amino]‐1‐phenylethanol ligand (1‐H2) prepared as a diastereomeric mixture or in racemic and meso forms, from known procedure, has been disodiated and complexed with ZrCl4. The precatalysts (mix‐1‐ZrCl2, rac‐1‐ZrCl2, and meso‐1‐ZrCl2) were used in combination with methylaluminoxane and found to be active for the polymerization of 1‐hexene and 1‐octene. The high molecular weight polyhexenes (PHs) and polyoctenes (POs) thus obtained were isotactic in nature and showed a negligible amount of end groups arising from the chain termination reactions. In PHs and POs, there was linear correlation in the modified Arrhenius plot (the natural logarithm of the number‐average molecular weight vs. the reciprocal of the temperature), indicating the presence of a single active species. The enantiomerically pure titanium precatalyst ((R,R)‐1‐TiCl2), when employed for the polymerization of 1‐hexene, was found to be active and the modified Arrhenius plot showed linear dependence demonstrating presence of a single active species. The analogous titanium precatalysts (mix‐1‐TiCl2, rac‐1‐TiCl2, and meso‐1‐TiCl2) obtained from known procedures were also found to be active for the polymerization of 1‐octene. The rac‐1‐TiCl2 precatalyst demonstrated a sigmoidal behavior in the modified Arrhenius plot for the POs and the mix‐1‐TiCl2 precatalyst showed an exponential type of behavior. The obtained POs seemed to have small amounts of chain termination via β‐hydride elimination alone. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3599–3610, 2007 相似文献
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