モノチオマレミドの熱可逆 [2 + 2] フォトダイマーおよびその内在的にリサイクル可能なコバルントネットワーク
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PubMedで要約を見る
まとめ
この要約は機械生成です。新しいリサイクル可能なクロスリンクされた材料は,光活性化結合と熱誘発脱結合を使用します. このチオマライミドプラットフォームは,高度なポリマーネットワークの効率的な再処理とクローズドループリサイクルを可能にします.
科学分野
- ポリマー化学
- 材料科学
- 有機化学
背景
- 本質的にリサイクル可能なクロスリンクされた材料の開発は,可逆結合における不利な化学的均衡のために困難です.
- 既存の方法は,結合の均衡を制御するために,しばしば外部操作を必要とします.
研究 の 目的
- 単体置換チオマライミドを用いた新しい可逆化学プラットフォームを導入する.
- リサイクル可能なポリマーネットワークの光活性化結合と熱誘発解鎖を実証する.
主な方法
- 小分子チオマレミド [2 + 2] フォトジマーを使用し,繰り返し結合/解約サイクルを行いました.
- 多機能チオマライミド反応剤を合成して 交互にリンクされたネットワークを作りました
- 再利用性を評価するために温度調節フォトレオロジーを採用した.
主要な成果
- 完全で独立した光活性化共電結合と120°C以上の熱解約が達成される.
- 最初の構成要素を再生する5つの熱/光サイクルで完全な変換が実証されています.
- 熱したときに分解し,粘性のある液体に戻ります.
結論
- ティオマライミドベースの熱セットは,複数のUVクロスリンクと熱解凍サイクルを通じて,本質的なリサイクル性を示す.
- ティオマライミドの熱的に可逆的な光分解は再処理と閉ループリサイクルのための新しい機会を提供します.
- このプラットフォームはダイナミックなポリマーネットワークの可能性を広げています.
関連する概念動画
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.
Electrocyclic reactions are highly stereospecific. For a substituted polyene, the stereochemical outcome...
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.
The reaction occurs between the highest occupied molecular orbital (HOMO) of one π component and the lowest unoccupied molecular orbital (LUMO) of the other. These are...
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
Thermally-induced [2 + 2] cycloadditions are symmetry forbidden. This is because the ground state HOMO of one ethylene molecule and the LUMO of the other ethylene are out of phase, preventing a concerted suprafacial-suprafacial overlap.
Absorption...
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.
![[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement](https://visualize.jove.com/wp-content/cache/webp/204799746147bbcc0dfb820e4fd9fa51.webp)
The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.
From a molecular orbital perspective, the rearrangement can be viewed as the interaction between the ground state frontier orbitals of the allyl anion and cation. Under thermal conditions, the...
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