Claesson Per M, Dedinaite Andra, Rojas Orlando J
Department of Chemistry, Surface Chemistry, Royal Institute of Technology, Drottning Kristinas väg 51, SE-100 44, Stockholm, Sweden.
Adv Colloid Interface Sci. 2003 Jul 1;104:53-74. doi: 10.1016/s0001-8686(03)00036-8.
Adsorbed layers of polyelectrolytes have been studied with atomic force microscopy (AFM) and the interferometric surface force apparatus (SFA). Particular emphasis was put on determining the effect of the polyelectrolyte charge density on surface topography, and the effect of the polyelectrolyte coating on the adhesive properties. The AFM was employed to image individual polymer chains at low adsorption densities and to characterize the layer topography and coverage at higher adsorption densities. The adhesive properties between two polyelectrolyte-coated surfaces in air were determined as a function of the number of contacts made at any given spot. The data provide evidence for formation of electrostatic bridges, particularly when highly charged polyelectrolytes are used. Further, material transport between the surfaces is observed when the polyelectrolyte is either highly charged or have a very low charge density. For intermediate charge densities we could not observe any indication of material transfer. The adhesion between one polyelectrolyte-coated surface and one bare surface was initially higher than that between two polyelectrolyte-coated surfaces. However, due to material transfer between the two surfaces the adhesion decreased significantly with the number of times that the surfaces were driven into contact. For the polyelectrolytes of the lowest charge density the results suggest that entanglement effects contribute to the adhesive interaction. The modification of the adhesion by polyelectrolytes in practical systems such as in the case of dry-strength additives to improve paper resistance is also considered.
已使用原子力显微镜（AFM）和干涉表面力仪（SFA）对聚电解质吸附层进行了研究。特别强调确定聚电解质电荷密度对表面形貌的影响，以及聚电解质涂层对粘附性能的影响。AFM用于在低吸附密度下对单个聚合物链成像，并在较高吸附密度下表征层的形貌和覆盖率。测定了空气中两个聚电解质涂层表面之间的粘附性能，作为在任何给定位置进行接触次数的函数。数据为静电桥的形成提供了证据，特别是在使用高电荷聚电解质时。此外，当聚电解质电荷密度很高或非常低时，会观察到表面之间的物质传输。对于中等电荷密度，我们未观察到任何物质转移的迹象。一个聚电解质涂层表面与一个裸表面之间的粘附力最初高于两个聚电解质涂层表面之间的粘附力。然而，由于两个表面之间的物质转移，粘附力随着表面接触次数的增加而显著降低。对于电荷密度最低的聚电解质，结果表明缠结效应有助于粘附相互作用。还考虑了聚电解质在实际系统中对粘附力的改性，例如在干强添加剂以提高纸张强度的情况下。
