1,6-ヘプタディエネの2状態生協調ポリメリゼーションによるポリ ((1,3-メチレンサイクロヘキサン) のステレオエンジニアリング
Kaitlyn E Crawford1, Lawrence R Sita
1Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA.
Journal of the American Chemical Society
|May 23, 2013
まとめ
研究者らは,1,6-ヘプタディエンのポリメリゼーション中にダイナミックなメチル群交換を制御し,様々な微細構造を持つポリ (-1,3-メチレンサイクロヘキサン) を生成し,大量特性とブロックコポリマー行動に影響を与えました.
科学分野:
- ポリマー化学のポリマー化学について
- マテリアルサイエンス 材料科学
背景:
- リビング・コーディネーション・ポリメリゼーションは,ポリマーアーキテクチャの正確な制御を提供します.
- ダイナミックなメチル群交換は,ポリマーの性質と形態学に影響を与えることができます.
研究 の 目的:
- 生物の協調ポリメリゼーションにおけるダイナミックなメチル群交換を外部から制御する.
- 系統的に変化するステレオ化学的微構造を持つポリー ((1,3-メチレンサイクロヘキサン) を生成する.
- マイクロストラクチャの散発特性への影響を調査し,コポリマー行動をブロックする.
主な方法:
- 1,6-ヘプタディエンの生協調ポリメリゼーション.
- 活性種と休眠種間のダイナミックなメチル群交換の外部制御.
- ステレオ化学的微細構造の体系的な変化.
- ポリマーとブロック共ポリマーの散発特性および固体マイクロフェーズ行動の特徴化.
主要な成果:
- 制御された微細構造で,ポリ (1,3-メチレンサイクロヘキサン) 物理形態のスペクトルが生成されました.
- この戦略は,ポリ (1,3-メチレンサイクロヘキサン) の散発特性をうまく操作した.
- ブロックコポリマーであるポリー ((1,3-メチレンサイクロヘキサン) -b-ポリ ((1-ヘキセン) の固体マイクロフェーズ行動が影響を受けた.
結論:
- ダイナミックメチル群交換の外部制御は,ポリマー微細構造のチューニングのための効果的な戦略です.
- この制御により,ポリ[1,3-メチレンサイクロヘキサン]の量産特性を調整することができます.
- このアプローチは,ブロックコポリマーの振る舞いを修正するのに適用できます.
関連する概念動画
01:17Thermal Electrocyclic Reactions: Stereochemistry
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.
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.
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
00:53Olefin 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...
01:16Olefin 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...
02:35Free-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.