サイクロファンベースのPd(II) アルファダイミン触媒を用いたエチレンの極性モノマーとの共ポリマー化に関する機械的調査
1Department of Chemistry, University of California, 1102 Natural Sciences 2, Irvine, California 92697, USA.
Journal of the American Chemical Society
|August 12, 2009
まとめ
この研究では,サイクロファンのリガンドを持つパラジウム触媒が,エチレンとメチルアクリlate (MA) のコポリマーへの高組み込みを可能にすることを明らかにしています. これは,リガンドが標準的な触媒と異なり,モノメア交換を阻害するからです.
科学分野:
- 有機金属化学 有機金属化学
- ポリメリゼーション触媒
- 機械学研究 機械学研究
背景:
- 以前の研究で,Pd (II) サイクロファンの触媒にアクリラートが多く組み込まれていることが示された.
- 標準的なPd(II) アルファダイミン触媒は,コポリメリゼーションにおいて正常なカートン・ハメット運動を示します.
研究 の 目的:
- Pd(II) サイクロファンベースのアルファ-ダイミン触媒を用いたエチレン/メチルアクリラート (MA) コポリメリゼーションの詳細なメカニズム調査を実施する.
- 以前に観察された異常に高いMAの組み込みの理由を理解するために.
主な方法:
- 研究されたエチレン/MAコポリメリゼーション運動.
- 2D EXSY NMRおよび1H NMRスペクトロスコピーを用いて研究されたオレフィン交換率.
- オレフィン交換の均衡定数と活性化障壁を決定する.
主要な成果:
- サイクロファンリガンドの軸阻害作用は,オレフィン置換と均衡を阻害する.
- エチレン交換率は,サイクロファン触媒の100倍以上で,アサイクリック触媒の100倍よりも遅かった.
- オレフィン交換の高度な活性化障壁が観察され,移住者の挿入障壁に匹敵する.
結論:
- サイクロファンのリガンドによる遅いオレフィン交換は,前均衡を防ぐ.
- これにより,エチレン/MA共ポリメリゼーションにおけるモノマー選択性が低下し,コモノマーが多く組み込まれます.
- 触媒の設計は,コポリマー組成を制御するための新しい戦略を提供します.
さらに関連する動画
関連する概念動画
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.
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...
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...
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,...
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
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...
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)
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...


