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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Roles of Enthalpy, Entropy, and Hydrogen Bonding in the Lower Critical Solution Temperature Behavior of Poly(ethylene oxide)/Water Solutions
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Roles of Enthalpy, Entropy, and Hydrogen Bonding in the Lower Critical Solution Temperature Behavior of Poly(ethylene oxide)/Water Solutions

机译：焓，熵和氢键在聚环氧乙烷/水溶液的较低临界溶液温度行为中的作用

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摘要

Analysis of the temperature and composition dependence of the excess thermodynamic properties for oligomers of poly(ethylene oxide) (PEO) in aqueous solution obtained from molecular dynamics simulations reveals that the lower critical solution temperature (LCST) behavior of PEO/water solutions is enthalpy-driven. At lower temperatures, the formation of ether-water hydrogen bonds results in a very favorable ΔG~(EX) consistent with the consolubility of PEO and water. Increasing temperature leads to a dramatic reduction in favorable ether-water interactions due to break-up of ether-water hydrogen bonding, while relatively persistent water-water hydrogen bonding maintains the energetic penalty associated with disrupted water-water interactions upon insertion of the ether. The entropy gain associated with the break-up of ether-water hydrogen bonds and reduction in the structure of hydrating water with increasing temperature is insufficient to offset the unfavorable enthalpic effects associated with the break-up of the ether-water hydrogen bonds.
机译：对分子动力学模拟获得的水溶液中聚环氧乙烷（PEO）低聚物的过量热力学性质的温度和成分依赖性的分析表明，PEO /水溶液的较低临界溶液温度（LCST）行为是焓-驱动。在较低温度下，醚-水氢键的形成会产生非常有利的ΔG〜（EX），与PEO和水的溶解度一致。由于醚-水氢键的破坏，温度升高导致有利的醚-水相互作用急剧降低，而相对持久的水-水氢键保持了与醚插入时破坏的水-水相互作用相关的能量损失。与醚-水氢键断裂相关的熵增益以及随着温度升高水化水的结构的减少不足以抵消与醚-水氢键断裂相关的不利的焓效应。

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