Djikaev Y S, Ruckenstein Eli
Department of Chemical and Biological Engineering, SUNY at Buffalo, 403 Furnas Hall, Buffalo, NY 14260, USA.
J Colloid Interface Sci. 2009 Aug 15;336(2):575-83. doi: 10.1016/j.jcis.2009.04.032. Epub 2009 Apr 17.
When two solute particles in water sufficiently approach each other, the disruption of water-water hydrogen bonds in their first hydration layers gives rise to an additional contribution to their overall interaction. Here we present a probabilistic approach to examining interactions between two identical parallel plates whereof the surfaces are covered with uniformly distributed hydrophobic and hydrophilic sites. The proposed approach allows one to determine the average number of hydrogen bonds per water molecule in the first hydration shell of a plate. Because of the constraint imposed by the proximity to the plate, a water molecule forms less hydrogen bond in this shell than in the bulk medium. As a result, the water molecules prefer the latter to the former, even though a bond is stronger in the former than in the latter. The interplay of these factors results in an additional contribution to the overall plate interaction which is attractive and naturally short-range, appearing only when the distance between the plates is smaller than five lengths of a hydrogen bond. At a given distance, it monotonically increases from 0 to its maximum value as the fraction of hydrophobic surface area on a plate increases from 0 to 1. When this fraction is 0.5, this contribution can be up to two orders of magnitude larger than the van der Waals interaction (depending on the water density in the vicinity of a plate).
当水中的两个溶质粒子充分靠近彼此时，其第一水化层中水分子间氢键的破坏会对它们的整体相互作用产生额外的贡献。在此，我们提出一种概率方法来研究两个相同平行板之间的相互作用，这两个平行板的表面覆盖着均匀分布的疏水和亲水位点。所提出的方法能够确定平板第一水化层中每个水分子的平均氢键数。由于靠近平板所施加的限制，一个水分子在这个水化层中形成的氢键比在本体介质中少。因此，水分子更喜欢本体介质而非平板附近，尽管前者中的氢键比后者中的更强。这些因素的相互作用对平板的整体相互作用产生了额外的贡献，这种贡献具有吸引力且自然是短程的，仅当平板之间的距离小于氢键长度的五倍时才会出现。在给定距离下，随着平板上疏水表面积分数从0增加到1，它从0单调增加到最大值。当该分数为0.5时，这种贡献可能比范德华相互作用大两个数量级（取决于平板附近的水密度）。
