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相关概念视频

Colloids03:22

Colloids

Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles that are visible to the naked eye or can be seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved...
Free-Radical Chain Reaction and Polymerization of Alkenes02:35

Free-Radical Chain Reaction and Polymerization of Alkenes

The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.
π Molecular Orbitals of 1,3-Butadiene01:24

π Molecular Orbitals of 1,3-Butadiene

Conjugated dienes have lower heats of hydrogenation than cumulated and isolated dienes, making them more stable. The enhanced stabilization of conjugated systems can be understood from their π molecular orbitals.
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
Olefin Metathesis Polymerization: Overview01:13

Olefin Metathesis Polymerization: Overview

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 of a...
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)01:16

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

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...
Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)00:53

Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)

Acyclic diene metathesis polymerization or ADMET polymerization involves cross-metathesis of terminal dienes, such as 1,8-nonadiene, to give linear unsaturated polymer and ethylene. As ADMET is a reversible process, the formed ethylene gas must be removed from the reaction mixture to complete the polymerization process.
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...

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相关实验视频

Updated: Jul 22, 2026

Using Polystyrene-block-poly(acrylic acid)-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization
09:02

Using Polystyrene-block-poly(acrylic acid)-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization

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由金属制成的聚烯球体,以非相互作用的聚烯为支.

Roscoe1, Frechet, Walzer

  • 1S. B. Roscoe and J. M. J. Frechet, Department of Chemistry, University of California, Berkeley, CA 94720, USA. J. F. Walzer and A. J. Dias, Baytown Polymer Center, Exxon Chemical Company, 5200 Bayway Drive, Baytown, TX 77520, USA.

Science (New York, N.Y.)
|April 29, 1998
PubMed
概括

一种新型的聚乙烯支器防止了烯聚合物聚合过程中的催化剂失活,使得聚合物珠内具有均的催化位点. 这种方法可以产生具有可控制尺寸的均聚烯珠.

科学领域:

  • 聚合物化学 聚合物化学
  • 催化剂是一种催化剂.
  • 材料科学 材料科学 材料科学

背景情况:

  • 金属催化剂为olefin聚合提供高活性,但易被传统的基解除活化.
  • 支持催化剂在同质系统上提供了处理优势,但支持相互作用可能是有害的.

研究的目的:

  • 为金属催化剂开发一种非相互作用的支持,以防止破坏性相互作用.
  • 保持支持的催化剂的好处,同时提高其稳定性和性能在olefin聚合.

主要方法:

  • 合成了一种非相互作用的,轻微交联的,甲基化聚烯支体.
  • 支持的金属催化剂是通过对聚钢珠进行特定试剂的连续处理来制备的.
  • 催化剂位点在聚钢珠中均分布.

主要成果:

  • 开发的聚乙烯支有效避免了与金属催化剂的破坏性相互作用.
  • 聚合发生在支珠中,导致同质的催化场所.
  • 乙烯和1-烯的共聚化产生了离散的,球形的多烯珠 (0.3-1.4毫米).
  • 通过调整聚合时间来控制聚合烯珠的大小.

结论:

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  • 一种新型的聚烯支系统对金属催化烯聚合有效.
  • 这种方法克服了基于的支的局限性,提供了更好的催化剂稳定性.
  • 该方法允许生产具有调节尺寸的均聚烯珠.