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Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration02:34

Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration

The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
Anionic Chain-Growth Polymerization: Overview01:20

Anionic Chain-Growth Polymerization: Overview

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,...
Anionic Chain-Growth Polymerization: Mechanism01:04

Anionic Chain-Growth Polymerization: Mechanism

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 acceptor.
Cationic Chain-Growth Polymerization: Mechanism00:57

Cationic Chain-Growth Polymerization: Mechanism

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 generated carbocation,...
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: 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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Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
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Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

Published on: November 27, 2015

2つの状態のアンサ-メタロセン複合体を用いたプロピレンポリメリゼーションに対する対照効果.

Muqtar Mohammed1, Marcio Nele, Abdulaziz Al-Humydi

  • 1Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1.

Journal of the American Chemical Society
|June 26, 2003
PubMed
まとめ
この要約は機械生成です。

この研究では,プロピレンポリメリゼーションをメタルロセンの触媒および様々な共同イニシアターを使用して調査しました. ポリマーの微細構造は,カウンテリオン選択によって大きく影響を受けず,触媒の振る舞いは,本質的なステレオ選択性ではなく,主にオペレーティングレジームによって異なる.

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Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by &#960;-&#960; Stacking Interactions
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A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes
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A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes

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関連する実験動画

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Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
07:28

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

Published on: November 27, 2015

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10:53

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by π-π Stacking Interactions

Published on: October 10, 2016

A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes
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A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes

Published on: February 27, 2017

科学分野:

  • ポリマー化学のポリマー化学について
  • 有機金属化学 有機金属化学
  • カタリシス カタリシス カタリシス

背景:

  • メタロセンの触媒は,調節可能な特性を提供し,オレフィンポリメリゼーションに不可欠です.
  • 触媒性能に対する共同イニシアターとカウンターイオンの影響を理解することは,ポリマーマイクロ構造の制御の鍵です.
  • プロピレンポリメリゼーションは,複雑な触媒メカニズムを研究するためのモデルシステムを提供します.

研究 の 目的:

  • 不対称なアンサ-メタロセン複合体を用いてプロピレンポリメリゼーションに作用する異なる共同イニシアター (メチラルミノキサン,B(C(6) F(5)) ((3),[Ph(3) C][B(C(6) F(5)) ((4)) の効果を調査する.
  • 触媒構造,共同イニシアター,その結果生じるポリプロピレン (PP) マイクロ構造の関係を解明する.
  • 触媒の行動とポリマーの戦術性に対するモノマー濃度の影響を調査する.

主な方法:

  • 非対称なアンサ-メタロセンの複合体の合成と応用 (Me(2) Y(Ind) CpMMe(2)).
  • プロピレンポリメリゼーション実験は,異なるモノマー濃度で実施されました.
  • ポリマーの微細構造の分析,戦術性およびペンタド分布を含む.
  • 基本的触媒パラメータ (例えば,伝播,逆転率) を決定するための運動モデリング.

主要な成果:

  • Me(2)Si(Ind)CpZrMe(2) から派生した触媒は,急速な連鎖逆転条件下で動作し,PPの微細構造は対極から大きく独立している.
  • ポリプロピレンの戦術性は,特定の触媒/共同イニシアター組合せ (Me(2) C (((Ind) CpHfMe(2) / PMAOまたは [Ph(3) C][B(C(6) F ((5)) ((4)) ]) のモノマー濃度に敏感でした.
  • B ((C ((6) F ((5)) ((3)) で活性化された触媒は,モノメア濃度に対して微細構造が不変であるステレオレギュラーPPを生成し,一貫した動作体制を示唆した.

結論:

  • 触媒の性能の主要な違いは,固有のステレオ選択性ではなく,動作モード (挿入比率と逆転比率) に由来する.
  • 作業体制に関して観測されたカウンターリオンの順番は,調整能力に基づく期待から逸脱している.
  • この研究は,メタルロセン触媒プロピレンポリメリゼーションにおける触媒設計と反応条件を通じたポリマー微構造の微妙な制御の洞察を提供します.