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相关概念视频

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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Anionic Chain-Growth Polymerization: Overview01:20

Anionic Chain-Growth Polymerization: Overview

2.1K
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,...
2.1K
Anionic Chain-Growth Polymerization: Mechanism01:04

Anionic Chain-Growth Polymerization: Mechanism

2.1K
The mechanism for anionic chain-growth polymerization involves initiation, propagation, and termination steps. In the initiation step, a nucleophilic anion, such as butyl lithium, initiates the polymerization process by attacking the π bond of the vinylic monomer. As a result, a carbanion, stabilized by the electron‐withdrawing group, is generated. The resulting carbanion acts as a Michael donor in the propagation step and attacks the second vinylic monomer, which acts as a Michael...
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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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Radical Chain-Growth Polymerization: Mechanism01:09

Radical Chain-Growth Polymerization: Mechanism

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The radical chain-growth polymerization mechanism consists of three steps: initiation, propagation, and termination of polymerization. The polymerization initiates when a free radical generated from the radical initiator adds to the unsaturated bond in the monomer. The unpaired electron of the free radical and one π electron in the unsaturated bond creates a σ bond between the free radical and the monomer. As a result, the other π electron in the unsaturated bond converts this...
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Controlled Synthesis and Fluorescence Tracking of Highly Uniform PolyN-isopropylacrylamide Microgels
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Controlled Synthesis and Fluorescence Tracking of Highly Uniform PolyN-isopropylacrylamide Microgels

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上转换粒子辅助的NIR聚合使微域梯度光聚化在粒子间长度尺度上成为可能.

Peng Hu1, Hang Xu1, Yue Pan1

  • 1International Research Center for Photoresponsive Molecules and Materials, Jiangnan University, Wuxi, 214122, Jiangsu, PR China.

Nature communications
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概括

上转化颗粒辅助NIR聚合 (UCAP) 能够使光聚合物材料具有高交叉连接和低收缩应力. 这种新的方法通过在凝前释放应力来增强机械性能.

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科学领域:

  • 聚合物化学 聚合物化学
  • 材料科学 材料科学 材料科学
  • 光聚合的光聚合方式.

背景情况:

  • 在光聚合物中同时实现高交叉连接和低收缩应力是具有挑战性的.
  • 传统的紫外线聚合技术往往会导致严重的内部压力.
  • 提高性能的光聚合物材料需要仔细控制固化过程.

研究的目的:

  • 引入和研究一种新的光聚合方法,使用上转换粒子辅助的NIR聚合 (UCAP).
  • 证明UCAP能够降低收缩应力,同时提高固化材料的机械性能.
  • 阐明UCAP实现这些改进的独特机制.

主要方法:

  • 利用在NIR激发后发射UV-VIS光的上转化粒子.
  • 实施一个以上转换粒子为中心的域限梯度光聚合过程.
  • 监测固化系统的状态 (液体,凝) 和功能组转换.
  • 将机械性能和收缩应力与传统紫外线聚合物的比较.

主要成果:

  • 在粒子中心域内,UCAP会诱导梯度光聚合.
  • 固化系统保持流动性,直到高功能组转换,在凝之前释放压力.
  • 经UCAP固化材料表现出高凝点转换率和显著较低的收缩应力.
  • 通过UCAP固的材料与传统的UV固对应物相比,具有优越的机械性能.

结论:

  • 向上转换粒子辅助的NIR聚合 (UCAP) 提供了一种独特的机制,以克服交叉连接和收缩应力之间的权衡.
  • UCAP 便于制备具有增强机械强度和降低内部应力的高性能光聚合物材料.
  • 这种方法为开发先进的光聚合物应用提供了有希望的进步.