Theory of hydration forces between surfaces
Theory of hydration forces between surfaces
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DOI：
10.1021/la960672w
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发表时间：
1997-04-02
期刊：
影响因子：
3.9
通讯作者：
Besseling, NAM
中科院分区：
文献类型：
--
作者：
Besseling, NAM
对水化层在平面上的干涉所产生的表面力提出了统计热力学理论。该理论是对先前提出的晶格流体理论的推广。在这个理论中，考虑了水分子之间依赖于取向的相互作用。研究了几种对相邻水有不同影响的模型表面。如果表面的主要作用是影响邻近液体的局部密度，而不是水分子的局部取向分布，那么两个这样的表面之间产生的力是吸引的。这在对水有高亲和力和低亲和力的表面都会遇到。然而，如果一个表面的主要作用是影响相邻水层中的方向分布，则两个表面之间的相互作用是排斥的。这种排斥力与水合层中氢键的破坏有关。当表面之间的距离不太小时，相互作用随距离呈指数衰减。如果表面同时影响局部密度和取向分布，这两种机制同时起作用。随后的相互作用可以是表面分离的非单调函数。这些结果与实验和Marcelja和Radic的现象学方法的推广是一致的。此外，现象学顺序参数现在可以用分子术语来确定。与相同表面之间的斥力相关的序参数是质子供体/质子受体不匹配。与引力相关的是局部过剩密度。
A statistical thermodynamic theory is presented for the surface forces arising from the interference of hydration layers at planar surfaces. The theory is a generalization of a previously presented lattice fluid theory of water. In this theory the orientation dependent interactions between water molecules are taken into account. Several model surfaces that have different effects upon adjoining water, are examined. If the predominant effect of the surface is to influence the local density of the adjoining liquid but not the local orientation distribution of the water molecules, then the ensuing force between two such surfaces is attractive. This is encountered in surfaces with both a low and a high affinity for water. However, if the main effect of a surface is to influence the orientational distribution in adjoining water layers, the interaction between two such surfaces is repulsive. This repulsive force is associated with the disruption of hydrogen bonding in the hydration layer. For not too small distances between the surfaces, the interactions decay exponentially with distance. Both mechanisms operate simultaneously if the surfaces influence both the local density and the orientational distribution. Then the ensuing interaction can be a nonmonotonous function of surface separation. These results are consistent with experiments and with a generalization of Marcelja and Radic's phenomenological approach. Moreover, the phenomenological order parameters can now be identified in molecular terms. The order parameter associated with repulsion between identical surfaces is a proton-donor/proton-acceptor mismatch. The one associated with attraction is the local excess density.