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相关概念视频

Cationic Chain-Growth Polymerization: Mechanism00:57

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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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Step-Growth Polymerization: Overview01:03

Step-Growth Polymerization: Overview

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Step-growth or condensation polymerization is a stepwise reaction of bi or multifunctional monomers to form long-chain polymers. As all the monomers are reactive, most of the monomers are consumed at the early stages of the reaction to form small chains of reactive oligomers, which then combine to form long polymer chains in the late stages. Hence, the reaction has to proceed for a long time to achieve high molecular weight polymers.
Many natural and synthetic polymers are produced by...
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Anionic Chain-Growth Polymerization: Overview01:20

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The polymerization process that involves carbanion as an intermediate is called anionic polymerization. It is also a type of addition or chain-growth polymerization. Anionic polymerization gets initiated by a strong nucleophile such as an organolithium or a Grignard reagent. The most commonly used initiator for anionic polymerization is butyl lithium. Monomers involved in anionic polymerization must possess a vinyl group bonded to one or two electron-withdrawing groups. For instance,...
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Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
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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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The introduction of polyesters has brought major development to the textile industry. The wrinkle-free behavior of polyester blends has eliminated the need for starching and ironing clothes.
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具有高单体选择性的Poly ((ε-caprolactone) 的定向脱聚合.

Rulin Yang1,2, Wei Wei1,2, Guangqiang Xu1,2,3

  • 1Key Laboratory of Photoelectric Conversion and Utilization of Solar Energy, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China.

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概括

这项研究引入了新型 (BisSalen) Al催化剂,用于选择性化学回收聚ε-烯酸乙烯 (PCL) 的单体 (CRM). 这些催化剂实现了高产量的e-caprolactone单体,促进了可持续的聚合物回收利用.

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可生物降解的聚乙烯.连锁链末端的背后谤化学回收到单体的化学回收.封闭式循环的 封闭式循环聚乙烯 (Poly(ε-caprolactone) 是一种聚乙烯的组成部分.选择性脱聚合选择性脱聚合.

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科学领域:

  • 聚合物化学 聚合物化学
  • 催化剂是一种催化剂.
  • 可持续材料 可持续材料

背景情况:

  • 化学回收到单体 (CRM) 提供闭环聚合物利用,但往往产生副产品与所需的单体一起.
  • 定向去聚合到单体对于高效的聚合物回收而不会损失性质至关重要.
  • 聚乙烯 (PCL) 脱聚合是可持续塑料管理的一个关键目标.

研究的目的:

  • 开发一种催化剂系统,用于PCL的高度选择性化学回收,将其转化为单体,e-caprolactone (e-CL).
  • 研究催化剂在控制脱聚合选择性的结构-活性关系.
  • 为选择性PCL脱聚合的机制提供理论见解.

主要方法:

  • 合成和应用具有封闭腔结构的创新 (BisSalen) Al 催化剂.
  • PCL的溶液相脱聚合.
  • 使用核磁共振 (NMR) 光谱分析脱聚合产品的分析.
  • 使用密度函数理论 (DFT) 计算的计算调查.

主要成果:

  • (BisSalen) Al催化剂实现了PCL的高度选择性去聚合,以≥99%的单体选择性为e-CL.
  • 在优化条件下,获得了93%的优异单体产量.
  • 核磁共振和DFT研究阐明了催化剂高选择性背后的机制.

结论:

  • 设计的 (BisSalen) Al 催化剂可实现PCL到e-CL的高效和选择性化学回收.
  • 催化剂结构,特别是封闭腔,对于指导脱聚合选择性至关重要.
  • 这项研究为设计针对性聚合物单体回收的先进催化剂提供了宝贵的指导.