非添加性イオン効果は,水中の熱反応性ポリマーの崩壊と膨張の両方を誘発する
Ellen E Bruce1, Pho T Bui2, Bradley A Rogers2
1Eduard-Zintl-Institut für Anorganische und Physikalische Chemie , Technische Universität Darmstadt , Alarich-Weiss-Straße 10 , D-64287 Darmstadt , Germany.
Journal of the American Chemical Society
|March 29, 2019
まとめ
強く,弱く水素化されたアニオンの混合物は,ポリマー溶液に非添加的に作用する. イオンコンペティションは,水分とインターフェースの相互作用を変化させることで,ポリ (N-イソプロピラクリアミド) の低い臨界溶液温度 (LCST) に影響します.
科学分野:
- 物理化学
- ポリマー科学
- 溶液化学
背景:
- ポリマー溶液の行動はイオンの存在に敏感です.
- ホフマイスターシリーズは,タンパク質とポリマーの溶解性に対するイオン特異的な影響を記述する.
- ポリマー溶液の性質を制御するには,イオン混合効果を理解することが重要です.
研究 の 目的:
- 混合アニオン (硫酸塩とヨウ化物) の低臨界溶液温度 (LCST) への非添加作用を調査する.
- これらの非添加的効果の背後にある分子メカニズムを計算的および実験的方法を使用して解明する.
主な方法:
- イオンとポリマーの相互作用をモデル化するために分子動力学 (MD) のシミュレーションが使用されました.
- 振動総周波数スペクトロスコーピー (VSFS) を用いて,ポリマー/水のインターフェイスを検出した.
- 固定された硫酸ナトリウム (Na2SO4) と異なるヨウ素ナトリウム (NaI) の濃度で実験を行った.
主要な成果:
- 低NaI濃度では,Na+カチオンが強く水分化されているSO42-) アニオンと好意的に結合し,I-アニオンがより水分化されます.
- より高いNaI濃度では,SO4 ((2-) アニオンは効果的に競合し,I-アニオンはPNiPAM/水界面に押し付けられる.
- これらの競合する水分と界面相互作用は,PNiPAM LCSTに非添加的効果をもたらします.
結論:
- 混合塩溶液中のPNiPAMのLCSTは,イオン水分とポリマーイオン相互作用の相互作用によって制御されます.
- この発見は,複雑な溶液系における競合するイオン効果を考慮することの重要性を強調している.
- このコンセプトは,ホフマイスターシリーズの強く,弱い水素化アニオンを含む様々な混合物に適用できます.
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