van Oss C J, Chaudhury M K, Good R J
Department of Microbiology, State University of New York, Buffalo 14214.
Adv Colloid Interface Sci. 1987 Nov;28(1):35-64. doi: 10.1016/0001-8686(87)80008-8.
Following the development of a methodology for determining the apolar components as well as the electron donor and the electron acceptor parameters of the surface tension of polar surfaces, surfaces of a number of quite common materials were found to manifest virtually only electron donor properties and no, or hardly, any electron acceptor properties. Such materials may be called monopolar; they can strongly interact with bipolar materials (e.g., with polar liquids such as water); but one single polar parameter of a monopolar material cannot contribute to its energy of cohesion. Monopolar materials manifesting only electron acceptor properties also may exist, but they do not appear to occur in as great an abundance. Among the electron donor monopolar materials are: polymethylmethacrylate, polyvinylalcohol, polyethyleneglycol, proteins, many polysaccharides, phospholipids, nonionic surfactants, cellulose esters, etc. Strongly monopolar materials of the same sign repel each other when immersed or dissolved in water or other polar liquids. The interfacial tension between strongly monopolar surfaces and water has a negative value. This leads to a tendency for water to penetrate between facing surfaces of a monopolar substance and hence, to repulsion between the molecules or particles of such a monopolar material, when immersed in water, and thus to pronounced solubility or dispersibility. Monopolar repulsion energies can far outweigh Lifshitz-van der Waals attractions as well as electrostatic and "steric" repulsions. In aqueous systems the commonly observed stabilization effects, which usually are ascribed to "steric" stabilization, may in many instances be attributed to monopolar repulsion between nonionic stabilizing molecules. The repulsion between monopolar molecules of the same sign can also lead to phase separation in aqueous solutions (or suspensions), where not only two, but multiple phases are possible. Negative interfacial tensions between monopolar surfactants and the brine phase can be the driving force for the formation of microemulsions; such negative interfacial tensions ultimately decay and stabilize at a value very close to zero. Strongly monopolar macromolecules or particles surrounded by oriented water molecules of hydration can still repel each other, albeit to an attenuated degree. This repulsion was earlier perceived as caused by "hydration pressure". A few of the relevant colloid and surface phenomena are reviewed and re-examined in the light of the influence of surface monopolarity on these phenomena.
在开发出一种用于测定非极性成分以及极性表面表面张力的电子供体和电子受体参数的方法之后，人们发现许多相当常见材料的表面实际上仅表现出电子供体性质，而没有或几乎没有任何电子受体性质。这类材料可称为单极性材料；它们能与双极性材料（如极性液体如水）发生强烈相互作用；但单极性材料的单一极性参数对其内聚能并无贡献。也可能存在仅表现出电子受体性质的单极性材料，但它们的数量似乎没那么多。属于电子供体单极性材料的有：聚甲基丙烯酸甲酯、聚乙烯醇、聚乙二醇、蛋白质、许多多糖、磷脂、非离子表面活性剂、纤维素酯等。当浸入或溶解于水或其他极性液体中时，具有相同符号的强单极性材料会相互排斥。强单极性表面与水之间的界面张力为负值。这导致水有渗透到单极性物质相对表面之间的趋势，因此，当浸入水中时，这种单极性材料的分子或颗粒之间会相互排斥，从而具有明显的溶解性或分散性。单极性排斥能可能远大于 Lifshitz -范德华引力以及静电和“空间位阻”排斥力。在水性体系中，通常观察到的稳定作用，通常归因于“空间位阻”稳定作用，在许多情况下可能归因于非离子稳定分子之间的单极性排斥。相同符号的单极性分子之间的排斥也可能导致水溶液（或悬浮液）中的相分离，其中不仅可能形成两相，还可能形成多相。单极性表面活性剂与盐水相之间的负界面张力可能是形成微乳液的驱动力；这种负界面张力最终会衰减并稳定在非常接近零的值。被取向的水化水分子包围的强单极性大分子或颗粒仍会相互排斥，尽管程度有所减弱。这种排斥作用早期被认为是由“水化压力”引起的。本文根据表面单极性对这些现象的影响，对一些相关的胶体和表面现象进行了综述和重新审视。
