论文标题
c $ _ \ text {n} $ TAB/聚苯乙烯磺酸盐的混合物在空气水接口：烷基链长度对表面活动和充电状态的影响
C$_\text{n}$TAB/Polystyrene Sulfonate Mixtures at Air-Water Interfaces: Effects of Alkyl Chain Length on Surface Activity and Charging State
论文作者
论文摘要
在水性溶液和空气水界面中研究了相对电荷的聚电解质和表面活性剂的结合和相行为。特别是，我们已经研究了聚支持聚苯二硫酸钠（NAPSS）和阳离子表面活性剂十二烷基三甲基溴化铵（C $ _ {12} $ TAB），四甲基二甲基二甲基三乙基溴化胺溴化氨基（C $ _ {C $ _ {14} $ TAB） （C $ _ {16} $ TAB）。为了揭示表面活性剂/聚电解质结合，混合物的聚集和相位分离，我们已经系统地浓度了，并使表面活性剂浓度保持固定。通过电泳迁移率和浊度测量获得了有关散装溶液中该行为的信息，而表面张力和总和频率产生（SFG）则进行了质疑。这使我们能够将批量与充电状态和表面活性剂的结合效率相关联。我们发现后两种强烈依赖表面活性剂的烷基链长度，并且随着表面活性剂的烷基链长度的增加，结合效率更高。这也导致了不同的相行为，如大量解决方案的浊度测量所示。在散装辅助界面中形成的充电中性聚集体对空气水接口，这种效果可能是由于C $ _ \ text {n} $ tab/pss复合物的疏水性增加引起的。 SFG光谱学证实了这一结论，我们观察到OH伸展带的强度降低，这表明表面充电的降低和形成具有可忽略的净电荷的接口。特别是在平衡两相区域的混合比下，我们观察到弱的OH强度，因此表面充电。
Binding and phase behavior of oppositely charged polyelectrolytes and surfactants were studied in aqueous bulk solutions and at air-water interfaces. In particular, we have investigated the polyanion poly(sodium 4-styrenesulfonate) (NaPSS) and the cationic surfactants dodecyltrimethylammonium bromide (C$_{12}$TAB), tetradecyltrimethylammonium bromide (C$_{14}$TAB) and cetyltrimethylammonium bromide (C$_{16}$TAB). In order to reveal surfactant/polyelectrolyte binding, aggregation and phase separation of the mixtures, we have varied the NaPSS concentration systematically and have kept the surfactants concentration fixed. Information on the behavior in the bulk solution was gained by electrophoretic mobility and turbidity measurements, while the surface properties were interrogated with surface tension and sum-frequency generation (SFG). This has enabled us to relate bulk to interfacial properties with respect to the charging state and the surfactants' binding efficiency. We found that the latter two are strongly dependent on the alkyl chain length of the surfactant and that binding is much more efficient as the alkyl chain length of the surfactant increases. This also results in a different phase behavior as shown by turbidity measurements of the bulk solutions. Charge neutral aggregates that are forming in the bulk ad-sorb to the air-water interface, an effect that is likely caused by the increased hydrophobicity of C$_\text{n}$TAB/PSS complexes. This conclusion is corroborated by SFG spectroscopy, where we observe a decrease in the intensity of OH stretching bands, which is indicative for a decrease in surface charging and the formation of interfaces with negligible net charge. Particularly at mixing ratios that are in the equilibrium two-phase region, we observe weak OH intensities and thus surface charging.
