Scholarlink

<p>Series of isoprene polymerizations with different polymerization time were performed by TiCl<sub>4</sub>/MgCl<sub>2</sub> type Ziegler-Natta catalysts. Polymerization kinetics showed catalytic activity had two-stage polymerization feature and the polymer chain microstructure gradually changed from the <i>trans</i>-1,4 and <i>cis</i>-1,4 mixed structure with low molecular weight (<i>M</i><sub>w</sub>) as well as broad molecular weight distribution (<i>M</i><sub>w</sub>/<i>M</i><sub>n</sub>) at the early stage, to the final high <i>trans</i>-1,4 structure with high <i>M</i><sub>w</sub> and narrow <i>M</i><sub>w</sub>/<i>M</i><sub>n</sub>. The high <i>trans</i>-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 <i>trans</i>-1,4 content, high <i>trans</i>-1,4-[II] dyad sequence concentration, high <i>trans</i>-<i>trans</i> unit linkage content and high crystallinity, which were generated by high <i>trans</i>-1,4 stereoselective active centers. While G fraction had low <i>trans</i>-1,4 content, low <i>trans</i>-1,4-[II] dyad sequence concentration, low <i>trans</i>-<i>trans</i> unit linkage content and low crystallinity, which were formed by the active center with low <i>trans</i>-1,4 stereoselectivity. The stereoselective transformation of active centers as well as <i>trans</i>-1,4 stereospecific polymerization mechanism of isoprene with TiCl<sub>4</sub>/MgCl<sub>2</sub>-AlEt<sub>3</sub> catalyst system was discussed.</p> Graphical Abstract

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

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

  • 期刊论文

  • 发表日期：

    2025年7月14日

查看全文
  • Jing Zhou,
  • Gongguo Zhang,
  • Chongdian Si,
  • Manman Jin,
  • Aihua He,
  • Qingtao Niu

摘要

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 (Mw) as well as broad molecular weight distribution (Mw/Mn) at the early stage, to the final high trans-1,4 structure with high Mw and narrow Mw/Mn. 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