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相关概念视频

Molecular Weight of Step-Growth Polymers01:08

Molecular Weight of Step-Growth Polymers

2.7K
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...
2.7K
Polymers: Molecular Weight Distribution01:10

Polymers: Molecular Weight Distribution

4.7K
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.
4.7K
Polymers: Defining Molecular Weight01:01

Polymers: Defining Molecular Weight

3.7K
Unlike small molecules with definite molecular weights, polymers are a mixture of individual polymer chains of varying lengths, each with a unique molecular weight.  So, the molecular weight of a polymer is expressed as an average value based on the average size of the polymer chains. The two most common forms of averages used for polymers are the number average molecular weight and weight average molecular weight.
The number average molecular weight (Mn) is the summation of the number...
3.7K
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)01:16

Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)

3.1K
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
3.1K
Step-Growth Polymerization: Overview01:03

Step-Growth Polymerization: Overview

4.3K
Step-growth or condensation polymerization is a stepwise reaction of bi or multifunctional monomers to form long-chain polymers. As all the monomers are reactive, most of the monomers are consumed at the early stages of the reaction to form small chains of reactive oligomers, which then combine to form long polymer chains in the late stages. Hence, the reaction has to proceed for a long time to achieve high molecular weight polymers.
Many natural and synthetic polymers are produced by...
4.3K
Polymer Classification: Architecture01:14

Polymer Classification: Architecture

3.7K
Polymers are classified as linear or branched on the basis of their chain architecture. The polymer chains in linear polymers have a long chain-like structure with minimal to no branching at all. Even if a polymer features large substituent groups on the monomer, which appear as branches to the skeleton, it is not considered a branched polymer. A branched polymer contains secondary polymer chains that arise from the main polymer chain. The branching occurs when the polymer growth shifts from...
3.7K

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相关实验视频

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Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers
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Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers

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在环膨胀聚合中控制温度的循环聚分子重量

Jinxing Jiang1, Ge Yao2, Yaqin Cui1

  • 1Key Laboratory of Advanced Optoelectronic Functional Materials of Gansu Province, Key Laboratory for New Molecule Materials Design and Function of Gansu Universities, College of Chemical Engineering and Technology, Tianshui Normal University, Tianshui 741001, China.

Journal of the American Chemical Society
|October 2, 2025
PubMed
概括

这项研究通过调整聚合温度来精确控制循环聚分子重量. 这种方法允许在高玻璃过渡温度下进行可调节的聚甲化物合成.

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Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes
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Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes
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科学领域:

  • 聚合物化学
  • 材料科学

背景情况:

  • 通过环膨胀聚合物合成循环聚合物具有挑战性,特别是在控制分子重量方面.
  • 精确的分子重量控制对于定制聚合物特性至关重要.

研究的目的:

  • 开发一种方法来轻松控制循环聚的分子量.
  • 研究聚合温度和分子重量控制之间的关系.
  • 合成具有可调节分子量和高玻璃过渡温度的聚甲.

主要方法:

  • 使用循环的链增长聚合.
  • 调整聚合温度以调节聚合和循环的速度.
  • 使用凝透色谱,质谱和原子力显微镜进行了分子重量特征.

主要成果:

  • 聚甲糖的分子量得到了成功控制,在32.2~189.0kg/mol之间.
  • 在分子重量和聚合温度的自然对数之间观察到一个反向关系.
  • 由于基的加入,玻璃过渡温度达到116.6°C.

结论:

  • 调整聚合温度为控制循环聚分子量提供了一种有效的策略.
  • 这种方法有助于合成具有理想热性质的定制循环聚合物.