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相关概念视频

Radical Chain-Growth Polymerization: Overview01:10

Radical Chain-Growth Polymerization: Overview

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Chain-growth or addition polymerization is successive addition reactions of monomers with a polymer chain. In radical chain-growth polymerization, the reaction proceeds via a free-radical intermediate. The free radical is formed from radical initiators, which spontaneously generate free radicals by homolytic fission. Organic peroxides (such as dibenzoyl peroxide, as shown in Figure 1) or azo compounds are popular radical initiators. A low concentration ratio of radical initiator to monomer is...
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Radical Chain-Growth Polymerization: Chain Branching01:17

Radical Chain-Growth Polymerization: Chain Branching

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The skeletal structure of polymers synthesized via radical polymerization is always branched. For example, the polymerization of ethylene by radical polymerization results in a low-density grade of polyethylene with a heavily branched skeletal structure. Here, the radical site abstracts hydrogen from the growing chain, and the radical site shifts from the end (a primary carbon center) to anywhere within the growing chain (a secondary carbon center). Consequently, the part of the chain from the...
1.9K
Anionic Chain-Growth Polymerization: Mechanism01:04

Anionic Chain-Growth Polymerization: Mechanism

2.0K
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...
2.0K
Ziegler–Natta Chain-Growth Polymerization: Overview01:17

Ziegler–Natta Chain-Growth Polymerization: Overview

3.3K
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...
3.3K
Radical Chain-Growth Polymerization: Mechanism01:09

Radical Chain-Growth Polymerization: Mechanism

2.5K
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...
2.5K
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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Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction
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硬化自愈弹性体具有链式移动性的自愈弹性体.

Matthew Wei Ming Tan1,2, Patrick Michael Thornton3, Gurunathan Thangavel1

  • 1School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore.

Advanced science (Weinheim, Baden-Wurttemberg, Germany)
|June 13, 2024
PubMed
概括

在软弹性体中调整聚合物链的移动性可以提高骨折性和自我愈合. 这提高了软件设备的耐用性和运行寿命,通过允许更好的损坏恢复.

关键词:
链路流动性的链路流动性弹性体的弹性体是什么断裂的性 断裂的性通过气结合,形成了气结合.这是一种自我愈合的疗法.

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科学领域:

  • 材料科学 材料科学 材料科学
  • 聚合物化学 聚合物化学

背景情况:

  • 软弹性体对于现代设备至关重要,但它们的使用寿命因易受损坏而受到限制.
  • 提高骨折性和自我愈合能力对于提高这些材料的耐用性和寿命至关重要.

研究的目的:

  • 调查方法,以提高骨折性和自我愈合在碳氧化功能化聚氨.
  • 了解聚合物链流动性在实现这些改进材料性能方面的作用.

主要方法:

  • 加入增塑剂和热处理来调整聚合物链的流动性.
  • 断裂性测试,包括双悬臂梁测试,以评估材料性能.
  • 不同的温度 (80-120°C) 和增塑剂度 (最优的是3 wt.%) 来评估性能增强.

主要成果:

  • 温度从80°C上升到120°C显著提高了骨折的恢复工作 (2.86到123.7MJ m-3).
  • 在最佳的塑化剂 (3重量%) 和温度 (40°C) 条件下,破裂性分别从16.3提高到19.9和25.6kJ m-2.
  • 碳酸键和链的移动性被确定为能量消散和应力再分配的关键机制,导致裂变.

结论:

  • 调整聚合物链流动性是一种有效的策略,可以同时提高柔软弹性体的断裂性和自我愈合.
  • 这些改进有助于防止损坏,并促进更好的恢复,延长软设备的功能寿命.
  • 了解治愈接口的断裂力学对于预测材料行为和自我治愈弹性体的故障预防至关重要.