Chemistry Department, Ecole Normale Supérieure, UMR ENS-CNRS-UPMC 8640, Paris, France.
Phys Chem Chem Phys. 2011 Nov 28;13(44):19911-7. doi: 10.1039/c1cp21916b. Epub 2011 Sep 6.
The reorientation dynamics of interfacial water molecules was recently shown to change non-monotonically next to surfaces of increasing hydrophilicity, with slower dynamics next to strongly hydrophobic (apolar) and very hydrophilic surfaces, and faster dynamics next to surfaces of intermediate hydrophilicities. Through a combination of molecular dynamics simulations and analytic modeling, we provide a molecular interpretation of this behavior. We show that this non-monotonic dependence arises from two competing effects induced by the increasing surface hydrophilicity: first a change in the hydration structure with an enhanced population of water OH bonds pointing toward the surface and second a strengthening of the water-surface interaction energy. The extended jump model, including the effects due to transition-state excluded volume and transition-state hydrogen-bond strength, provides a quasi-quantitative description of the non-monotonic changes in the water reorientation dynamics with surface hydrophilicity.
界面水分子的重取向动力学最近被证明在亲水表面的增加下呈非单调变化，在强疏水性（非极性）和非常亲水表面附近的动力学较慢，而在中等亲水性表面附近的动力学较快。通过分子动力学模拟和分析建模的结合，我们提供了对此行为的分子解释。我们表明，这种非单调依赖性源于表面亲水性增加引起的两种竞争效应：首先是水合结构的变化，水中 OH 键的数量增加，指向表面；其次是水-表面相互作用能的增强。扩展跳跃模型，包括由于过渡态排斥体积和过渡态氢键强度引起的效应，为水重取向动力学随表面亲水性的非单调变化提供了准定量描述。
