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Polymers: Molecular Weight Distribution01:10

Polymers: Molecular Weight Distribution

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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.
3.5K
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
Ziegler–Natta Chain-Growth Polymerization: Overview01:17

Ziegler–Natta Chain-Growth Polymerization: Overview

3.4K
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...
3.4K
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
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
Polymers02:34

Polymers

35.9K
The word polymer is derived from the Greek words “poly” which means “many” and “mer” which means “parts”. Polymers are long chains of molecules composed of repeating units of smaller molecules, known as monomers. They either occur naturally, such as DNA and proteins, or can be constructed synthetically, like plastics. They have varied structural characteristics, such as linear chains, branched chains, or complex networks, that contribute to the...
35.9K

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相关实验视频

Updated: Jul 27, 2025

DNA Nanotubes as a Versatile Tool to Study Semiflexible Polymers
08:00

DNA Nanotubes as a Versatile Tool to Study Semiflexible Polymers

Published on: October 25, 2017

6.9K

一个带状模型用于内马基聚合物网络的带状模型.

Harmeet Singh1, Epifanio G Virga2

  • 1Laboratory for Computation and Visualization in Mathematics and Mechanics, Institute of Mathematics, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.

Journal Of Elasticity
|June 9, 2023
PubMed
概括

我们开发了一种关于阴性聚合物网络 (NPN) 丝带的理论,预测蛇形变形对热或光的反应. 这项工作简化了复杂的材料行为,用于带应用.

科学领域:

  • 材料科学 材料科学 材料科学
  • 聚合物物理 聚合物物理
  • 软物质物理学 软物质物理学

背景情况:

  • 阴性聚合物网络 (NPNs) 将的弹性与液晶特性相结合.
  • NPNs对外界的刺激,如热量和光线做出反应.
  • 现有的模型描述了NPN板,但不是带.

研究的目的:

  • 为了获得NPN带的变形的理论模型.
  • 简化一个 2D 纸张能量模型到一个带式能量模型.
  • 用一个具体的例子来演示带的行为.

主要方法:

  • 使用了缩小尺寸的方法.
  • 从先前存在的二维板块能量模型中提取了带能量.
  • 适用于矩形NPN带模型的边界条件.

主要成果:

  • 开发了NPN带变形的理论框架.
  • 在模型带上成功预测了飞机内蛇形变形.
  • 衍生能源模型适用于NPN带.

结论:

  • 尺寸缩小方法有效地模拟了NPN带机制.
关键词:
纳米性弹性体是什么?阴性聚合物网络 阴性聚合物网络具有光活性的弹性材料带带理论 带带理论软物质的弹性 软物质的弹性

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Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives
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Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives

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Scalable Nanohelices for Predictive Studies and Enhanced 3D Visualization
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Scalable Nanohelices for Predictive Studies and Enhanced 3D Visualization

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相关实验视频

Last Updated: Jul 27, 2025

DNA Nanotubes as a Versatile Tool to Study Semiflexible Polymers
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DNA Nanotubes as a Versatile Tool to Study Semiflexible Polymers

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Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives
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Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives

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Scalable Nanohelices for Predictive Studies and Enhanced 3D Visualization
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Scalable Nanohelices for Predictive Studies and Enhanced 3D Visualization

Published on: November 12, 2014

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  • NPN 带可以表现出复杂的,刺激响应的变形.
  • 这一理论为设计新的NPN带式设备提供了基础.