Trans-1,4- stereospecific copolymerization of isoprene and butadiene catalyzed by TiCl4/MgCl2 type Ziegler-Natta catalyst II. Copolymerization Kinetics and Mechanism
Trans-1,4- stereospecific copolymerization of isoprene and butadiene catalyzed by TiCl4/MgCl2 type Ziegler-Natta catalyst II. Copolymerization Kinetics and Mechanism
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DOI：
10.1016/j.polymer.2018.04.007
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发表时间：
2018-05
期刊：
影响因子：
4.6
通讯作者：
Q. Niu;Weitian Li;Xiangyu Liu;Riguo Wang;Aihua He
中科院分区：
文献类型：
--
作者：
Q. Niu;Weitian Li;Xiangyu Liu;Riguo Wang;Aihua He
Stereospecific copolymerization mechanism of isoprene (Ip) and butadiene (Bd) with heterogeneous TiCl4/MgCl2-Al(i-Bu)3Ziegler-Natta catalyst was investigated for the first time in this paper. Copolymerization kinetics of isoprene and butadiene revealed that copolymers with highcis-1,4 units were observed in the initial stage, then thetrans-1,4/cis-1,4 ratio increased gradually to the finally dominanttrans-1,4-sequecnc with increasing polymerization time. The Al/Ti ratio influenced the catalytic efficiency,trans-1,4-sequecnc percentage and the butadiene incorporation (FBd). The copolymers obtained at different conversion and Al/Ti ratio were isolated to a series of fractions by stepwise isothermal crystallization fractionation from 80 °C to −20 °C. Thetrans-1,4-unit percentage,trans-transandtrans-cisplacement, butadiene-isoprene (BI or IB) dyad sequence concentration, FBd,molecular weight and molecular weight distribution of the main fractions were analyzed by1H NMR,13C NMR, TGA, GPC, DSC and WAXD characterization, which provided powerful evidences for the presence and evolution of active centers with different catalytic stereospecificity. Therefore, the possible active centers andtrans-1,4 stereospecific copolymerization mechanism of isoprene and butadiene using heterogeneous Ziegler-Natta catalyst system was proposed accordingly.
