Lubrication by organized soft matter
Lubrication by organized soft matter
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DOI：
10.1039/b918415e
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发表时间：
2010-01-01
期刊：
影响因子：
3.4
通讯作者：
Claesson, P. M.
中科院分区：
文献类型：
--
作者：
Dedinaite, A.;Pettersson, T.;Claesson, P. M.
利用原子力显微镜胶体探针技术研究了在无表面活性剂和存在表面活性剂的情况下，浸在水溶液中的聚电解质表面之间的相互作用和摩擦力。研究发现，承载力的性质对层的润滑性能起决定性作用。当负载由一个允许界面层具有高流动性的力承载时，可以获得低摩擦力，而吸引的表面力通常会增加摩擦。高电荷的聚电解质和带相反电荷的表面活性剂在散装溶液中结合形成具有明确内部结构的配合物。在表面，类似结构的聚电解质表面活性剂层自发形成。这样的层具有很高的承载能力，只要保持层的完整性，摩擦系数就很低。有趣的是，当负载逐步增加时，摩擦力作为负载的函数显示出一些尖锐的峰值，这被认为是由于聚电解质-表面活性剂层中的结构重排。卸载时，尽管层与层之间存在粘连，但获得的摩擦力非常低。为了保持良好的润滑性能，必须在溶液中存在表面活性剂，然而，在初始吸附步骤之后，不需要在散装中存在聚电解质。其原因是聚电解质本质上的不可逆吸附。
The AFM-colloidal probe technique has been used to explore surface interactions and friction forces between polyelectrolyte-coated surfaces immersed in aqueous solutions in the absence and presence of surfactant. It is found that the nature of the load bearing forces is decisive for the lubricating properties of the layers. Low frictional forces are obtained when the load is carried by a force that allows the interfacial layer to have a high fluidity, whereas attractive surface forces most often increase the friction. Highly charged polyelectrolytes and oppositely charged surfactants associate in bulk solution to form complexes with a well-defined internal structure. At the surface, similarly structured polyelectrolyte-surfactant layers are spontaneously formed. Such layers have a high load bearing capacity, and the friction coefficient is very low as long as the integrity of the layer remains intact. Interestingly, when the load is increased step-wise the friction force as a function of load displays some sharp peaks, which are identified as being due to structural rearrangements in the polyelectrolyte-surfactant layer. On unloading very low frictional forces are obtained despite the presence of an adhesion between the layers. To maintain the favorable lubricating properties it is essential to have surfactants present in solution, whereas, after the initial adsorption step, there is no need to have the polyelectrolyte present in the bulk. The reason for this is the essentially irreversible adsorption of the polyelectrolyte.