マイクロスケールのリアルタイムポリマー粘度-触媒活性関係
Contact us if these videos are not relevant.
Contact us if these videos are not relevant.
PubMedで要約を見る
まとめ
この要約は機械生成です。活体ポリマーの粘度変化をリアルタイムで測定した. 粘度が増加すると,触媒ポリメリゼーションの速度が遅くなり,大量のポリマー特性に影響するマイクロスケールの異質性が明らかになった.
科学分野
- ポリマー化学
- 材料科学
- 化学工学
背景
- ポリマーの成長は触媒の微小環境の物理的性質を動的に変化させる.
- これらのリアルタイムの物理的変化を理解することは,ポリメリゼーション運動と最終的なポリマー特性を制御するために不可欠です.
研究 の 目的
- ポリマーの成長中の触媒の微小環境の物理的変化をリアルタイムで定量化します.
- 微小環境の変化が微小スケールの化学触媒とポリメリゼーション速度に及ぼす影響を調査する.
- 微小粘度と分子レベルでの触媒活動との直接的な関係を確立する.
主な方法
- 光学的に透明な生体ポリマー粒子をイメージする新しい方法の開発.
- 光強度顕微鏡と光寿命画像顕微鏡を使用して,微環境の粘度と化学活動の同時,高空間時間解像度イメージング.
- 個々のポリマー粒子の内部と間の微小粘度変動の定量化
主要な成果
- マイクロ環境の粘度の増加は,触媒環開きメタテシスのポリメリゼーション率の低下と直接相関していた.
- 観察された粘度の変化はモノマーに依存し,クロスリンクされたポリマーはクロスリンクされていないポリマーよりも大きな粘度増加を示した.
- 集計測定技術では観測できない微小粘度における有意な空間的異質性が検出されました.
結論
- 微小環境の粘度が微小スケールの触媒活動に直接影響を及ぼし,活性部位への拡散を制限する可能性がある.
- ポリマー粒子の内部の微小粘度における空間的変動は,非均質な散発ポリマー特性を引き起こす可能性があります.
- 開発されたイメージング技術は,ポリマーの構造と触媒機能の間のダイナミックな相互作用について前例のない洞察を提供します.
関連する概念動画
For any given polymer, the weight average molecular weight (Mw) is higher than, if not equal to, the number average molecular weight (Mn). The only situation in which the weight average molecular weight and the number average molecular weight are equal is when a polymer consists only of chains with equal molecular weight. However, this never happens in a synthetic polymer, since it is difficult to control the polymerization process up to a molecular level with accuracy to a hundred percent.
Step-growth or condensation polymerization is a stepwise reaction of bi or multifunctional monomers to form long-chain polymers. As all the monomers are reactive, most of the monomers are consumed at the early stages of the reaction to form small chains of reactive oligomers, which then combine to form long polymer chains in the late stages. Hence, the reaction has to proceed for a long time to achieve high molecular weight polymers.
Many natural and synthetic polymers are produced by...
Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta...
The radical chain-growth polymerization mechanism consists of three steps: initiation, propagation, and termination of polymerization. The polymerization initiates when a free radical generated from the radical initiator adds to the unsaturated bond in the monomer. The unpaired electron of the free radical and one π electron in the unsaturated bond creates a σ bond between the free radical and the monomer. As a result, the other π electron in the unsaturated bond converts this...
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...
Step growth polymerization involves bi or multifunctional monomers. Bifunctional monomers react to form linear step growth polymers, whereas multifunctional monomers react to form non-linear or branched polymers.
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...