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相关概念视频

Polymer Classification: Crystallinity01:21

Polymer Classification: Crystallinity

3.0K
Unlike ionic or small covalent molecules, polymers do not form crystalline solids due to the diffusion limitations of their long-chain structures. However, polymers contain microscopic crystalline domains separated by amorphous domains.
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
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Anionic Chain-Growth Polymerization: Overview01:20

Anionic Chain-Growth Polymerization: Overview

2.2K
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,...
2.2K
Cationic Chain-Growth Polymerization: Mechanism00:57

Cationic Chain-Growth Polymerization: Mechanism

2.4K
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...
2.4K
Polymers: Molecular Weight Distribution01:10

Polymers: Molecular Weight Distribution

3.7K
For any given polymer, the weight average molecular weight (Mw) is higher than, if not equal to, the number average molecular weight (Mn). The only situation in which the weight average molecular weight and the number average molecular weight are equal is when a polymer consists only of chains with equal molecular weight. However, this never happens in a synthetic polymer, since it is difficult to control the polymerization process up to a molecular level with accuracy to a hundred percent.
3.7K
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...
2.1K
Radical Chain-Growth Polymerization: Overview01:10

Radical Chain-Growth Polymerization: Overview

2.5K
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...
2.5K

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Updated: Aug 31, 2025

Synthesis of Monodisperse Cylindrical Nanoparticles via Crystallization-driven Self-assembly of Biodegradable Block Copolymers
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一个晶体1D动态共价聚合物

Elisabet De Bolòs1, Marta Martínez-Abadía1, Félix Hernández-Culebras1

  • 1POLYMAT, University of the Basque Country UPV/EHU, Avenida de Tolosa 72, Donostia-San Sebastián 20018, Spain.

Journal of the American Chemical Society
|August 22, 2022
PubMed
概括

研究人员使用动态共价化学合成了一种晶体一维聚合物. 这一突破使得我们能够更好地了解聚合物的特性,并创造出具有更强的电荷传输能力的材料.

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科学领域:

  • 聚合物化学
  • 材料科学
  • 固态物理

背景情况:

  • 晶体一维聚合物对于理解材料中的结构性质关系至关重要.
  • 由于无形或半晶相的趋势,实现晶体一维聚合物具有挑战性.
  • 这些材料具有增强的热,机械和导电性能.

研究的目的:

  • 报告溶液中的晶体一维聚合物的合成.
  • 调查结构与财产的关系,特别是运输费用.
  • 展示一种制造有序聚合物材料的方法.

主要方法:

  • 聚合物合成的动态共价化学.
  • 微晶电子衍射用于结构确认.
  • 收费运输研究和理论计算

主要成果:

  • 在溶液中成功合成晶体一维聚合物.
  • 通过微晶电子衍射明确证实了聚合物的结构.
  • 证明 π 叠加的链条可以为电荷传输创造最佳通道.

结论:

  • 通过动态共价化学实现晶体一维聚合物的合成.
  • 这种 π 堆叠结构是聚合物优良的电荷传输特性的关键.
  • 这项工作推动了具有定制电子特性的先进聚合物材料的开发.