The search for the hydrophobic force law.
The search for the hydrophobic force law.
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DOI：
10.1039/b926184b
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发表时间：
2010
影响因子：
3.4
通讯作者：
Israelachvili J
中科院分区：
文献类型：
--
作者：
Hammer MU;Anderson TH;Chaimovich A;Shell MS;Israelachvili J
经过近30年对疏水相互作用的研究，对疏水力规律的探索仍在继续。事实上，问题比答案多，并且对于名义上相似的条件，以及显然对于纳米、微米和宏观表面，实验数据常常是相当不同的。这导致了这样的结论，即实验观察到的力-距离关系要么是不同的“基本”相互作用的组合，要么是疏水力定律，如果有一个，是复杂的-取决于许多参数。到目前为止，在所有实验中测得的唯一出乎意料的强吸引力的范围是D = 100-200 Ω，大致呈指数增长，下降到10-20 Ω，然后更急剧地下降到D = 0时的粘附接触，或者对于幂律势，有效地在D = 2 Ω时。在此范围（100-200 Ω）中测得的力，特别是粘附力要强得多，并且与非导电电介质的连续VDW力（Lifshitz理论）具有不同的距离依赖性。我们提出了一个三区力定律，用于疏水表面之间观察到的力：在第一，从100-200欧姆到数千欧姆，主导力是由互补的静电域或相对表面上的补丁和/或桥接蒸汽腔产生的;一种“纯的”但仍未被很好理解的“长程疏水力”在约150至约15 μ m的第二区域占主导地位，这可能是由于与水的“质子跳跃”极化率相关的Hamaker常数增强;而低于约10-15 ℃接触时，存在另一种与表面相关的水结构效应相关的“纯短程疏水力”，在水-疏水界面处的水分子和H-键的取向和/或密度中引起变化。我们提出了最近的SFA和其他实验结果，以及一个简化的模型，水的基础上的球对称的潜力，是能够捕捉到一些基本特征的疏水缔合。这样一个模型可能是有用的理论研究的HI在广泛的尺度上观察到的SFA实验。
After nearly 30 years of research on the hydrophobic interaction, the search for the hydrophobic force law is still continuing. Indeed, there are more questions than answers, and the experimental data are often quite different for nominally similar conditions, as well as, apparently, for nano-, micro-, and macroscopic surfaces. This has led to the conclusion that the experimentally observed force–distance relationships are either a combination of different ‘fundamental’ interactions, or that the hydrophobic force-law, if there is one, is complex – depending on numerous parameters. The only unexpectedly strong attractive force measured in all experiments so far has a range of D ≈ 100–200 Å, increasing roughly exponentially down to ~ 10–20 Å and then more steeply down to adhesive contact at D = 0 or, for power-law potentials, effectively at D ≈ 2 Å. The measured forces in this regime (100–200 Å) and especially the adhesive forces are much stronger, and have a different distance-dependence from the continuum VDW force (Lifshitz theory) for non-conducting dielectric media. We suggest a three-regime force-law for the forces observed between hydrophobic surfaces: In the first, from 100–200 Å to thousands of ångstroms, the dominating force is created by complementary electrostatic domains or patches on the apposing surfaces and/or bridging vapour cavities; a ‘pure’ but still not well-understood ‘long-range hydrophobic force’ dominates the second regime from ~ 150 to ~ 15 Å, possibly due to an enhanced Hamaker constant associated with the ‘proton-hopping’ polarizability of water; while below ~ 10–15 Å to contact there is another ‘pure short-range hydrophobic force’ related to water structuring effects associated with surface-induced changes in the orientation and/or density of water molecules and H-bonds at the water–hydrophobic interface. We present recent SFA and other experimental results, as well as a simplified model for water based on a spherically-symmetric potential that is able to capture some basic features of hydrophobic association. Such a model may be useful for theoretical studies of the HI over the broad range of scales observed in SFA experiments.
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