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相关概念视频

Olefin Metathesis Polymerization: Overview01:13

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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.
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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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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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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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The word polymer is derived from the Greek words “poly” which means “many” and “mer” which means “parts”. Polymers are long chains of molecules composed of repeating units of smaller molecules, known as monomers. They either occur naturally, such as DNA and proteins, or can be constructed synthetically, like plastics. They have varied structural characteristics, such as linear chains, branched chains, or complex networks, that contribute to the...
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Synthesis of Soft Polysiloxane-urea Elastomers for Intraocular Lens Application
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有氧基和无催化剂的动态共价聚氨

Wen-Xing Liu1,2, Chi Zhang3, Huan Zhang1,2

  • 1Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Research/Education Center for Excellence in Molecular Sciences, Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China.

Journal of the American Chemical Society
|May 31, 2017
PubMed
概括

这项研究引入了一种新型动态聚合物类型的多氧化尿素 (POU). 这些聚合物提供无催化剂,可治愈和可回收材料,具有出色的机械性能,克服了传统聚氨的局限性.

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科学领域:

  • 聚合物化学
  • 材料科学
  • 有机化学

背景情况:

  • 聚氨 (PU) 广泛使用,但由于有毒催化剂和热的加工能力差,因此面临限制.
  • 开发可持续的可加工替代品对于先进材料的应用至关重要.

研究的目的:

  • 合成和表征一种新的动态共价聚合物,即聚氧氨 (POU).
  • 研究POU的无催化剂合成,热可逆性和机械性能.
  • 探索POU作为传统聚氨的可持续替代品的潜力.

主要方法:

  • 在环境温度下多功能氧化物和六甲二酸盐 (HDI) 的未催化多添加.
  • 用各种溶剂,包括二甲 (DCM) 的动力学研究,以确定最佳的聚合条件.
  • 热重量测量分析和动态机械分析以评估热稳定性和可逆性.
  • 密度函数理论 (DFT) 的计算以阐明反应机制.

主要成果:

  • 在DCM中以30°C的温度在3小时内实现高聚合转化 (∼99%),产生线性POU.
  • 通过离合机制在约100°C时证明了热可逆的氧化碳酸盐键.
  • 相互连接的POU表现出无催化剂可治愈和可回收的特性.
  • DFT计算表明,氧化物中分离体中介于快速聚合和热可逆性.

结论:

  • 聚氧氨 (POU) 是一个有前途的新型动态共价聚合物.
  • 提供容易,无催化剂的制备,优良的机械性能和动态性能 (可治愈/可回收).
  • POU的独特特性源于可逆的氧胺-碳酸盐结合,由子双相介导,为可持续材料开发铺平了道路.