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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Temperature Dependence of Dimerization and Dewetting of Large-Scale Hydrophobes: A Molecular Dynamics Study
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Temperature Dependence of Dimerization and Dewetting of Large-Scale Hydrophobes: A Molecular Dynamics Study

机译：大型疏水物二聚和脱湿的温度依赖性：分子动力学研究

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We studied by molecular dynamics simulations the temperature dependence of hydrophobic association and drying transition of large-scale solutes. Similar to the behavior of small solutes, we found the association process to be characterized by a large negative heat capacity change. The origin of this large change in heat capacity is the high fragility of hydrogen bonds between water molecules at the interface with hydrophobic solutes; an increase in temperature breaks more hydrogen bonds at the interface than in the bulk. With increasing temperature, both entropy and enthalpy changes for association strongly decrease, while the change in free energy weakly varies, exhibiting a small minimum at high temperatures. At around T = T_s = 360 K, the change in entropy is zero, a behavior similar to the solvation of small nonpolar solutes. Unexpectedly, we find that at T_s, there is still a substantial orientational ordering of the interfacial water molecules relative to the bulk. Nevertheless, at this point, the change in entropy vanishes due to a compensating contribution of translational entropy. Thus, at T_s, there is rotational order and translational disorder of the interfacial water relative to bulk water. In addition, we studied the temperature dependence of the drying—wetting transition. By calculating the contact angle of water on the hydrophobic surface at different temperatures, we compared the critical distance observed in the simulations with the critical distance predicted by macroscopic theory. Although the deviations of the predicted from the observed values are very small (8—23%), there seems to be an increase in the deviations with an increase in temperature. We suggest that these deviations emerge due to increased fluctuations, characterizing finite systems, as the temperature increases.
机译：我们通过分子动力学模拟研究了疏水缔合的温度依赖性和大规模溶质的干燥转变。与小溶质的行为相似，我们发现缔合过程的特征是负热容变化很大。这种热容量大变化的根源是与疏水性溶质的界面处水分子之间氢键的高脆性。温度的升高比在界面处断裂更多的氢键。随着温度的升高，缔合的熵和焓变化都大大降低，而自由能的变化则微弱变化，在高温下表现出很小的最小值。在大约T = T_s = 360 K时，熵的变化为零，其行为类似于小的非极性溶质的溶剂化。出乎意料的是，我们发现在T_s处，界面水分子相对于主体仍然有大量的取向顺序。但是，此时，由于平移熵的补偿作用，熵的变化消失了。因此，在T_s处，界面水相对于大量水存在旋转次序和平移混乱。另外，我们研究了干燥-润湿转变的温度依赖性。通过计算不同温度下水在疏水表面上的接触角，我们将模拟中观察到的临界距离与宏观理论预测的临界距离进行了比较。尽管预测值与实测值的偏差很小（8-23％），但随着温度的升高，偏差似乎有所增加。我们建议这些偏差是由于温度升高而引起的波动增加而引起的，这是有限系统的特征。

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