POLYMER
·
2024
·
IF 4.1
Qingtao Niu,Aihua He,Chongdian Si,Guodong Liu,Mingxuan Xiao,Guifan Chen,Manman Jin
Four TiCl 4 /MgCl 2 Ziegler-Natta catalysts (Cat-1∼Cat-4) with titanium contents in the range of 0.038–0.578 wt% were synthesized by the chemical rout and used for isoprene polymerizations. Four catalysts had similar possessed rod-like morphologies and their surface areas gradually increased as Ti contents increased. Cat-1 with the lowest Ti content (0.038 wt%) had the highest catalytic activity (28039.6 g∙P/(g∙Ti∙h)). To our knowledge, this was the highest activity achieved for isoprene polymerization using the heterogeneous TiCl 4 /MgCl 2 Ziegler-Natta catalyst. With the increasing Ti content, the catalyst activity gradually decreased in the order of Cat-1 < Cat-2 < Cat-3 < Cat-4, whereas the trans -1,4 stereoselectivity increased. Cat-4 with the highest Ti content (0.578 wt %) gave highest trans -1,4 units (97.7 mol%). The polymers were mainly composed of fraction C, D and G. C and D had high trans -1,4 structure while G fraction had low trans -1,4 structure. The plausible stereospecific transformation models of MgCl 2 -supported Ziegler-Natta catalyst with different Ti contents were discussed.
研究领域:
催化
·
高分子化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Molecular Catalysis
·
2024
·
IF 3.9
Qingtao Niu,Aihua He,Chongdian Si,Guodong Liu,Bolin Dai,Manman Jin
Two TiCl 4 /MgCl 2 type Ziegler-Natta catalysts containing ethyl benzoate (EB) and dibutyl phthalate (DBP) as internal electron donors (ID) were prepared for isoprene polymerizations using five kinds of external electron donors (ED) (phenyltrimethoxysilane (ED-1), dicyclopentyl(dimethoxy)silane (ED-2), 2-butyl-2-ethyl-1,3-dimethoxypropane (ED-3), 1,3-dimethoxypropane (ED-4) and di(2-ethylhexyl)phthalate (ED-5)). The structure features of TiCl 4 /ID/MgCl 2 catalysts were characterized and the effect of ID and ED on polymerization behaviors was studied. EB had higher adsorption content on catalyst surface, higher catalytic activity and lower trans -1,4 stereoselectivity than DBP . Appropriate introduction of ED-1 and ED-2, expect ED-3, ED-4 and ED-5, caused the enhancement in polymerization activity and trans -1,4 content, while excess addition led to the deactivation. The effect of ED on equilibrium between selective activation and deactivation of active species significantly relied on the electron donor type and concentration.
研究领域:
高分子化学
·
催化
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
CATALYSIS LETTERS
·
2025
·Vol. 155
·期 8
·1-13
·
IF 2.4
Zhou Jing,Zhang Gongguo,Si Chongdian,Jin Manman,He Aihua,Niu Qingtao
Series of isoprene polymerizations with different polymerization time were performed by TiCl 4 /MgCl 2 type Ziegler-Natta catalysts. Polymerization kinetics showed catalytic activity had two-stage polymerization feature and the polymer chain microstructure gradually changed from the trans -1,4 and cis -1,4 mixed structure with low molecular weight ( M w ) as well as broad molecular weight distribution ( M w / M n ) at the early stage, to the final high trans -1,4 structure with high M w and narrow M w / M n . The high trans -1,4 units can enhance the tensile strength and hardness of the synthetic polyisoprenes, which are widely used for golf ball cover, medicinal material and shape memory material. Polymers were mainly isolated into Fraction C, D and G by the stepwise isothermal crystallization fractionation method. Fraction C and D had high trans -1,4 content, high trans -1,4-[II] dyad sequence concentration, high trans - trans unit linkage content and high crystallinity, which were generated by high trans -1,4 stereoselective active centers. While G fraction had low trans -1,4 content, low trans -1,4-[II] dyad sequence concentration, low trans - trans unit linkage content and low crystallinity, which were formed by the active center with low trans -1,4 stereoselectivity. The stereoselective transformation of active centers as well as trans -1,4 stereospecific polymerization mechanism of isoprene with TiCl 4 /MgCl 2 -AlEt 3 catalyst system was discussed. Graphical
研究领域:
高分子化学
·
有机合成
·
材料科学
·
催化
·
大分子化学
·
物理化学
✓ 已验证
产品关联
DOI
高影响因子
Molecular Catalysis
·
2020
·
IF 3.687
Wei Peng,Jianmei Xie,Junying Zhang,Xia Yang,Aihua He
The isoprene polymerization kinetics by using TiCl 4 /MgCl 2 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 (k p ), 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 ( M w ) 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 M w 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 M w .
研究领域:
高分子化学
·
催化化学
·
聚合物合成
·
材料科学
·
配位聚合
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）