Department of Chemistry, University of Oregon, Eugene, OR 97403, USA.
Proc Natl Acad Sci U S A. 2012 Feb 28;109(9):3226-31. doi: 10.1073/pnas.1200244109. Epub 2012 Feb 15.
Polyelectrolytes (PEs) are widely used in applications such as water purification, wastewater treatment, and mineral recovery. Although much has been learned in past decades about the behavior of PEs in bulk aqueous solutions, their molecular behavior at a surface, and particularly an oil-water interface where many of their applications are most relevant, is largely unknown. From these surface spectroscopic and thermodynamics studies we report the unique molecular characteristics that several common polyelectrolytes, poly(acrylic acid) and poly(methylacrylic acid), exhibit when they adsorb at a fluid interface between water and a simple insoluble organic oil. These PEs are found to adsorb to the interface from aqueous solution in a multistepped process with a very thin initial layer of oriented polymer followed by multiple layers of randomly oriented polymer. This additional layering is thwarted when the PE conformation is constrained. The adsorption/desorption process is highly pH dependent and distinctly different than what might be expected from bulk aqueous phase behavior.
聚电解质（PEs）在水净化、废水处理和矿物回收等应用中被广泛使用。尽管在过去几十年中，人们已经了解了 PEs 在本体水溶液中的行为，但它们在表面，特别是在许多应用最相关的油水界面处的分子行为在很大程度上仍是未知的。从这些表面光谱和热力学研究中，我们报告了几种常见的聚电解质，聚丙烯酸和聚甲基丙烯酸，在吸附于水和简单不溶有机油之间的流体界面时所表现出的独特分子特性。这些 PEs 被发现从水溶液中以多步过程吸附到界面上，最初是一层取向聚合物，然后是多层无规取向聚合物。当 PE 构象受到限制时，这种额外的分层会受到阻碍。吸附/解吸过程高度依赖于 pH 值，与从本体水相行为中可能预期的情况明显不同。
