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相关概念视频

Ziegler–Natta Chain-Growth Polymerization: Overview01:17

Ziegler–Natta Chain-Growth Polymerization: Overview

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Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta...
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Olefin Metathesis Polymerization: Overview01:13

Olefin Metathesis Polymerization: Overview

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Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists...
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Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)00:53

Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)

1.9K
Acyclic diene metathesis polymerization or ADMET polymerization involves cross-metathesis of terminal dienes, such as 1,8-nonadiene, to give linear unsaturated polymer and ethylene. As ADMET is a reversible process, the formed ethylene gas must be removed from the reaction mixture to complete the polymerization process.
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
1.9K
Free-Radical Chain Reaction and Polymerization of Alkenes02:35

Free-Radical Chain Reaction and Polymerization of Alkenes

7.9K
The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.
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Sharpless Epoxidation02:57

Sharpless Epoxidation

4.1K
The conversion of allylic alcohols into epoxides using the chiral catalyst was discovered by K. Barry Sharpless and is known as Sharpless epoxidation. The use of a chiral catalyst enables the formation of one enantiomer of the product in excess. This chiral catalyst is mainly a chiral complex of titanium tetraisopropoxide and tartrate ester (specific stereoisomer). The stereoisomer used in the chiral catalyst dictates the formation of the enantiomer of the product. In other words, the use of...
4.1K
Cationic Chain-Growth Polymerization: Mechanism00:57

Cationic Chain-Growth Polymerization: Mechanism

2.3K
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the...
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Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
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使用单位催化剂实现高乙烯聚合性能的战略.

Lujain Alrais1, Walid Al Maksoud1, Baraa Werghi1

  • 1KAUST Catalysis Center and Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia.

Chemical communications (Cambridge, England)
|October 3, 2023
PubMed
概括

这项研究开发了一种基于Ti(IV) 的新型催化剂,使用3D纤维化支 (KCC-1) 进行增强的乙烯聚合. 独特的催化剂结构显著提高了催化性能,产生高分子量高密度聚乙烯 (HDPE).

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科学领域:

  • 不同质的催化剂.
  • 有机金属化学 有机金属化学
  • 聚合催化剂的聚合.

背景情况:

  • 表面有机金属化学原理是设计先进催化剂的关键.
  • 具有特定形态和功能性的支对于催化剂性能至关重要.
  • 乙烯聚合需要高效的催化剂来生产有价值的聚乙烯材料.

研究的目的:

  • 合成和描述新型异质Ti (IV) 基催化剂用于乙烯聚合.
  • 为了研究3D纤维化支 (KCC-1) 对催化活性和聚合物特性的影响.
  • 探索功能化和结合在催化剂性能上的作用.

主要方法:

  • 通过表面有机金属化学合成一个基于Ti (IV) 的催化剂,通过表面有机金属化学定在3D KCC-1基支持上.
  • 使用FT-IR,固态NMR (1H, 13C),ICP-OES,CHNS分析和XPS进行了表征.
  • 在乙烯聚合过程中催化性能的评估和由此产生的高密度聚乙烯 (HDPE) 的分析.

主要成果:

  • 一个新的异质催化剂["Si-O-Si") "Si-O-") "Al-O-) TiNp3]成功合成和表征.
  • KCC-1的3D纤维形态和功能增强了反应剂扩散和定.
  • 催化剂在乙烯聚合过程中表现出了显著的活性,产生了分子量为3,200,000 g/mol的HDPE,PDI为2.3.

结论:

  • 结合功能化支的3D形态和电子特性,显著提高了催化性能.
  • 开发的基于Ti (IV) 的催化剂对于生产高分子量HDPE非常有效.
  • 该研究强调了支设计在烯聚合物的异质催化中的重要性.