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相关概念视频

Polymer Classification: Stereospecificity01:26

Polymer Classification: Stereospecificity

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Polymerization generates chiral centers along the entire backbone of a polymer chain. Accordingly, the stereochemistry of the substituent group has a significant effect on polymer properties. Polymers formed from monosubstituted alkene monomers feature chiral carbons at every alternate position in the polymer backbone. Relative to the predominant orientation of substituents at the adjacent chiral carbons, the polymer can exist in three different configurations: isotactic, syndiotactic, and...
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Polymer Classification: Crystallinity01:21

Polymer Classification: Crystallinity

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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...
2.7K
Molecular Weight of Step-Growth Polymers01:08

Molecular Weight of Step-Growth Polymers

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Step growth polymerization involves bi or multifunctional monomers. Bifunctional monomers react to form linear step growth polymers, whereas multifunctional monomers react to form non-linear or branched polymers.
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...
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Anionic Chain-Growth Polymerization: Mechanism01:04

Anionic Chain-Growth Polymerization: Mechanism

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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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Anionic Chain-Growth Polymerization: Overview01:20

Anionic Chain-Growth Polymerization: Overview

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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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相关实验视频

Updated: May 15, 2025

Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
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通过界面聚合制造产生的二维聚合物薄膜中的异型热导电性.

Yuxing Liang1, Kiana A Treaster2, Ayan Majumder3

  • 1Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, Pennsylvania 15213, United States.

ACS nano
|May 14, 2025
PubMed
概括

在二维聚合物 (2DP) 膜中观察到异型热传输. 这些材料的平面内导热率高于横平面导热率,这表明了先进的热管理应用的潜力.

关键词:
不同类型的热导电性异型热导电性.共价有机框架是共价有机框架.频域中的热反射率 (thermoreflectance) 是一个频域.高分辨率的热量计.分子动力学模拟,分子动力学模拟两个维的聚合物.

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科学领域:

  • 材料科学 材料科学 材料科学
  • 聚合物科学 聚合物科学
  • 热传输是一种热传输.

背景情况:

  • 二维聚合物 (2DPs) 是具有独特特性的新兴材料.
  • 了解它们的热传输特性对于电子和能源应用至关重要.
  • 热导电性的异性可用于有针对性的散热.

研究的目的:

  • 测量和分析2DP薄膜的异构热传输特性.
  • 为了研究薄膜结构和导热率之间的关系.
  • 探索2DPs在热管理方面的潜力.

主要方法:

  • 通过界面聚合制备独立的二氧化膜 (Per-PDA 和 TAPPy-PDA).
  • 使用悬浮热量计平台测量平面内导热率 (k).
  • 使用频域热反射率测量横平面导热率 (k).

主要成果:

  • 伊米连接的2DP片在平面内具有较高的导热率 (k),而不是横平面导热率 (k).
  • 在室温下观察到高达2.3的异性质比 (k/k).
  • 导热率与温度呈正相关性,归因于声子散射.

结论:

  • 观察到的异质性归因于刚性在平面内共价键和灵活的交叉平面相互作用之间的差异.
  • 分子动力学模拟预测原始晶体中异性质比率显著更高 (超过7).
  • 未来开发更高质量的2DP片预计将产生增强的导热率和异质性.