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相关概念视频

Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)00:53

Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)

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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...
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Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)01:16

Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)

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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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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...
2.0K
Cationic Chain-Growth Polymerization: Mechanism00:57

Cationic Chain-Growth Polymerization: Mechanism

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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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Types of Step-Growth Polymers: Polyesters01:20

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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.
Polyesters are commonly prepared from terephthalic acid and ethylene glycol; the crude product is known as poly(ethylene terephthalate) or PET. However, polyesters are synthesized industrially by transesterification of dimethyl terephthalate with ethylene glycol at 150 °C. The two reactants and the...
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一个伪块共聚化 通过细分选择性转化而获得循环交替的共聚物.

Hongxuan Zhu1, Fengzhuang Liu1, Hongxin Zhang1

  • 1Faculty of Materials Science and Engineering, Qinghai University, Qinghai 810016, People's Republic of China.

ACS macro letters
|January 21, 2025
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概括

合成循环聚合物是一项挑战. 这项研究使用共聚化过程中的宏分子转化,以创建具有可控尺寸和低分散性的循环交替共聚物.

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科学领域:

  • 聚合物化学 聚合物化学
  • 宏分子科学 宏分子科学
  • 有机合成 有机合成

背景情况:

  • 循环聚合物的高效合成是聚合物科学的重大挑战.
  • 循环聚合物与其线性对应物相比,具有独特的特性.
  • 开发用于循环聚合物合成的可控方法对于先进的材料应用至关重要.

研究的目的:

  • 开发一种用于有效合成循环交替共聚物的新方法.
  • 研究使用宏分子转化在创建宏循环结构中的应用.
  • 为了证明合成的循环聚合物的多功能性,以进一步发挥功能.

主要方法:

  • 3,4-二二和环氧化物的有机基催化环开环交替共聚化,使用聚乙烯氧化物作为宏观启动剂.
  • 在新形成的聚片段上进行选择性分子内转化 (backbiting).
  • 循环交替共聚物的隔离通过沉基于溶解度差异.

主要成果:

  • 成功合成了具有低分散度 (<1.2) 和受控的分子质量 (~3 kg mol-1) 的循环交替共聚物.
  • 证明了对环形大小的热力学控制,独立于单体与发动机的比率.
  • 使用质谱和显微镜可视化证实了宏环结构.
  • 利用循环共聚物制备循环刷型聚物,通过乙烯修饰和随后的移植聚合.

结论:

  • 伪块共聚化过程中的宏分子转化是循环聚合物合成的有效策略.
  • 开发的方法提供了对精确定义的循环交替共聚物的访问.
  • 合成的循环聚合物作为多功能平台,用于创建复杂的聚合物架构,如循环刷型聚合物.