Cohen Stuart M A, de Vos W M, Leermakers F A M
Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands.
Langmuir. 2006 Feb 14;22(4):1722-8. doi: 10.1021/la052720v.
Polymers adsorbing from a dilute solution onto the solvent-vapor interface generate a nonzero surface pressure. When the same polymers are end-grafted onto a surface such that a so-called polymer brush is formed, one will find that the solvent wets this compound interface partially. The partial wetting and the finite surface pressure are intimately linked properties of the polymer-solvent-vapor combination. It is shown that the spreading parameter in the wetting problem is proportional to the surface pressure in the adsorption case. Complete wetting is only possible when this surface pressure is nonpositive. The wetting characteristics are hardly influenced by the grafting density and chain length characterizing the brush. We argue that the grafted polymer chains can bridge to the solvent-vapor interface, thereby preventing the wetting film to become macroscopically thick. We present experimental data underpinning our self-consistent field analysis. Indeed, finite contact angles should be expected in various systems in which bridging attraction contributes to the disjoining pressure in wetting films.
从稀溶液吸附到溶剂 - 蒸汽界面的聚合物会产生非零表面压力。当相同的聚合物以端接枝的方式连接到表面从而形成所谓的聚合物刷时，人们会发现溶剂会部分润湿这个复合界面。部分润湿和有限表面压力是聚合物 - 溶剂 - 蒸汽组合紧密相关的特性。结果表明，润湿问题中的铺展参数与吸附情况下的表面压力成正比。只有当这个表面压力为非正时，完全润湿才有可能。润湿特性几乎不受表征刷子的接枝密度和链长的影响。我们认为接枝的聚合物链可以桥接到溶剂 - 蒸汽界面，从而防止润湿膜宏观变厚。我们给出了支持我们自洽场分析的实验数据。实际上，在各种系统中，当桥连吸引力对润湿膜中的分离压力有贡献时，应该预期会有有限的接触角。
