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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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Ziegler–Natta Chain-Growth Polymerization: Overview01:17

Ziegler–Natta Chain-Growth Polymerization: Overview

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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...
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Polymer Classification: Architecture01:14

Polymer Classification: Architecture

2.6K
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...
2.6K
Polymer Classification: Crystallinity01:21

Polymer Classification: Crystallinity

2.8K
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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Olefin Metathesis Polymerization: Overview01:13

Olefin Metathesis Polymerization: Overview

2.0K
Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists...
2.0K
Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

2.0K
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
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Predicting Catalyst Extrudate Breakage Based on the Modulus of Rupture
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使用分类器预测聚烯微结构的催化剂设计

Yin-Pok Wong1, Hyuk-Joon Jung1, Shiyun Lin1

  • 1Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095, United States.

Journal of the American Chemical Society
|January 23, 2025
PubMed
概括
此摘要是机器生成的。

研究人员开发了一种新的分类方法来发现用于制造非交替聚的催化剂. 这种方法确定了两种新的催化剂类别,改善了聚合物合成,并使已知的催化剂类型翻了一番.

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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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科学领域:

  • 聚合物化学
  • 催化科学

背景情况:

  • 通过一氧化碳 (CO) 和乙烯的共聚化合成非交替聚.
  • 目前用于该过程的催化剂有限,主要使用硫酸盐和二氧化物联体.

研究的目的:

  • 开发一种用于发现新型催化剂的预测分类方法.
  • 扩大能够合成具有控制CO含量的非交替多基的催化剂的范围.

主要方法:

  • 应用分类方法来预测催化剂的性能.
  • 对CO/乙烯共聚化新型复合物的选和鉴定.

主要成果:

  • 发现用于非交替聚合成的两种新类的复合物.
  • 与现有的催化剂相比,实现了含有较低CO的多基的合成.
  • 可以催化这种聚合的已知化合物的两倍.

结论:

  • 开发的分类器方法加速了选择性聚合物合成的催化剂的发现.
  • 这种方法扩大了用于非交替聚生产的催化剂的范围.
  • 该方法在选择性关键的催化剂发现中具有更广泛的应用潜力.