writer：1. Wei Peng, Jianmei Xie, Junying Zhang, Xia Yang*, Aihua He*
keywords：Heterogeneous Z-N catalyst，Titanium content，Trans-1,4-polyisoprene，Active species，Catalytic mechanism
source：期刊
Issue time：2020年
The isoprene polymerization kinetics by using TiCl4/MgCl2 type Ziegler-Natta catalysts (TMC) with different titanium contents were studied for better understanding the possible active-specie structures of heterogeneous Ziegler-Natta (Z-N) catalysts for conjugated diene polymerizations. The catalytic features including the catalytic activity (CA), number of active centers ([C*]/[Ti]), rate constant for polymerization (kp), stereoregularity of these TMC catalysts were studied. The low titanium content catalyst TMC-1 (Ti?=?0.09?wt.%) with more isolated mononuclear titanium species showed higher CA and yielded cis-1,4-/trans-1,4- mixed microstructure polyisoprene with low molecular weight (Mw) in the initial polymerization stage. The medium high titanium content catalyst TMC-2 (Ti?=?2.38?wt.%) with more clustered mononuclear titanium species showed lower CA and yielded cis-1,4-/trans-1,4- mixed microstructure polyisoprene with high Mw in the early stage of polymerization. The high titanium content catalyst TMC-3 (Ti?=?3.76?wt.%) presented lowest CA and yielded high trans-1,4- polyisoprene with higher Mw.