Stereoselective Synthesis and Chain Microstructure Control of Trans-1,4-polyisoprene Enabled Via TiCl4/MgCl2 Ziegler-Natta Catalyst

IF 2.3 4区化学 Q3 CHEMISTRY, PHYSICAL

Catalysis Letters Pub Date : 2025-07-14 DOI:10.1007/s10562-025-05101-w

Jing Zhou, Gongguo Zhang, Chongdian Si, Manman Jin, Aihua He, Qingtao Niu

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Abstract

Series of isoprene polymerizations with different polymerization time were performed by TiCl₄/MgCl₂ 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 TiCl₄/MgCl₂-AlEt₃ catalyst system was discussed.

Graphical Abstract

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TiCl4/MgCl2 Ziegler-Natta催化剂使反式-1,4-聚异戊二烯立体选择性合成及链结构控制

采用TiCl4/MgCl2型Ziegler-Natta催化剂，对不同聚合时间的异戊二烯进行了系列聚合。聚合动力学表明，催化活性具有两阶段聚合特征，聚合物链微观结构由早期低分子量（Mw）、宽分子量分布（Mw/Mn）的反式-1,4和顺式-1,4混合结构逐渐转变为高分子量（Mw）、窄分子量（Mw/Mn）的反式-1,4高结构。高反式-1,4单位可提高合成聚异戊二烯的抗拉强度和硬度，广泛用于高尔夫球罩、药材和形状记忆材料。采用等温逐步结晶分馏的方法将聚合物主要分离为C、D和G三个组分。组分C和D具有较高的反式-1,4含量、较高的反式-1,4-[II]二元序列浓度、较高的反式-反式单元键含量和较高的结晶度，这是由较高的反式-1,4立体选择性活性中心产生的。G组分反式-1,4含量低，反式-1,4-[II]二联体序列浓度低，反式-反式单元键含量低，结晶度低，这是由低反式-1,4立体选择性的活性中心形成的。讨论了TiCl4/MgCl2-AlEt3催化剂体系中活性中心的立体选择性转化和反式-1,4立体定向聚合机理。图形抽象

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来源期刊

Catalysis Letters 化学-物理化学

CiteScore

5.70

自引率

3.60%

发文量

327

审稿时长

1 months

期刊介绍： Catalysis Letters aim is the rapid publication of outstanding and high-impact original research articles in catalysis. The scope of the journal covers a broad range of topics in all fields of both applied and theoretical catalysis, including heterogeneous, homogeneous and biocatalysis. The high-quality original research articles published in Catalysis Letters are subject to rigorous peer review. Accepted papers are published online first and subsequently in print issues. All contributions must include a graphical abstract. Manuscripts should be written in English and the responsibility lies with the authors to ensure that they are grammatically and linguistically correct. Authors for whom English is not the working language are encouraged to consider using a professional language-editing service before submitting their manuscripts.