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相关概念视频

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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Potential Due to a Polarized Object01:29

Potential Due to a Polarized Object

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A neutral atom consists of a positively charged nucleus surrounded by a negatively charged electron cloud. When placed in an external electric field, the external electric force pulls the electrons and nucleus apart, opposite to the intrinsic attraction between the nucleus and the electrons. The opposing forces balance each other with a slight shift between the center of masses of the nucleus and the electron cloud, resulting in a polarized atom. On the other hand, a few molecules, like water,...
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Induced Electric Dipoles01:28

Induced Electric Dipoles

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A permanent electric dipole orients itself along an external electric field. This rotation can be quantified by defining the potential energy because the external torque does work in rotating it. Then, the potential energy is minimum at the parallel configuration and maximum at the antiparallel configuration. While the former is a stable equilibrium, the latter is an unstable equilibrium.
Since the absolute value of potential energy holds no physical meaning, its zero value can be chosen as per...
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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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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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Dielectric Polarization in a Capacitor01:31

Dielectric Polarization in a Capacitor

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The presence of a dielectric medium in a capacitor not only changes the voltage and capacitance but also affects the electric field. In general, dielectrics can be of two types: polar and nonpolar. In a polar dielectric, the positive and negative charges in the molecules are separated by a distance and hence have a permanent dipole moment. In contrast, no such charge separation exists in a nonpolar dielectric, however the nonpolar molecules get polarized in the presence of an external electric...
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用导电聚合物进行动态核极化.

Quentin Stern1, Guillaume Verhaeghe1, Théo El Daraï1,2

  • 1Université Claude Bernard Lyon 1, CRMN UMR-5082, CNRS, ENS Lyon, Villeurbanne, 69100, France.

Angewandte Chemie (International ed. in English)
|September 12, 2024
PubMed
概括
此摘要是机器生成的。

有机导电聚合物提供了一种新的方法,可以通过溶解动态核极化 (dDNP) 来超极化核旋转. 这种方法提高了核磁共振 (NMR) 的灵敏度,而不需要极低的温度或高磁场.

关键词:
导电性聚合物中的导电性聚合物.动态的核极化是动态的核极化.核磁共振是一种核磁共振.旋转超极化 旋转超极化

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科学领域:

  • 材料科学 材料科学 材料科学
  • 物理化学 物理化学
  • 频谱学是一种光谱学.

背景情况:

  • 液态核磁共振 (NMR) 的低灵敏性限制了其应用.
  • 溶解动态核极化 (dDNP) 通过极化核旋转来增强NMR灵敏度.
  • 目前的dDNP方法需要冷温度 (<2K) 和复杂的仪器仪表,这阻碍了广泛采用.

研究的目的:

  • 引入有机导电聚合物,特别是聚氨 (PANI),作为dDNP的极化矩阵的新类.
  • 用这些导电聚合物证明核旋转的超极化.
  • 探索奇拉导电聚合物的潜力,用于自旋选择性超极化.

主要方法:

  • 使用聚氨 (PANI) 作为溶解动态核极化 (dDNP) 的极化矩阵.
  • 在多孔导电聚合物中的宿主溶液中,研究了用于超极化13C旋转的继电DNP.
  • 在导电聚合物中探索了性诱导的旋转选择性,用于电子旋转超极化.

主要成果:

  • 使用PANI作为极化矩阵,达到高达5%的1H超极化.
  • 在导电聚合物矩阵中通过继电DNP成功超极化13C旋转.
  • 在没有低温或高电场的奇拉导电聚合物中,证明了接近统一的电子旋转超极化.

结论:

  • 有机导电聚合物,如PANI,是dDNP的有效极化矩阵.
  • 导电聚合物中的中继DNP使目标核旋转的超极化成为可能.
  • 导电聚合物中性诱导的自旋选择性为高效,低温,低场DNP提供了一个有前途的途径.