Hodges Chris, Biggs Simon, Walker Lynn
Institute of Particle Science and Engineering, University of Leeds, Leeds LS2 9JT, UK.
Langmuir. 2009 Oct 6;25(19):11503-8. doi: 10.1021/la901321h.
A quartz crystal microbalance (QCM) and an optical reflectometer (OR) have been used to investigate the adsorption behavior of two different variants of the surfactant-hydrotropic counterion system, alkane trimethylammonium vinylbenzoate (CnTVB), onto silica surfaces. The C18TVB variant, with a longer hydrocarbon tail, produced a three-stage adsorption isotherm in the OR, whereas the C16TVB surfactant showed a two-stage adsorption isotherm. This was explained in terms of the greater degree of hydrophobicity of the C18 carbon chain requiring a significantly higher concentration of surfactant to be present on the surface before any further adsorption can occur. A concentration dependent adsorption rate was observed for both surfactants, with the faster adsorption rate being detected for C18TVB. The OR data showed that each surfactant could be completely rinsed off with the flow of water into the OR cell. This was not observed with the QCM data, where only a partial rinse off was seen. The difference between the two techniques was hypothesized to be due to the ability of the QCM to detect both interfacial and bulk behavior thus complicating the interpretation of the adsorption data.
已使用石英晶体微天平（QCM）和光学反射仪（OR）来研究表面活性剂-水溶助长性抗衡离子体系的两种不同变体，即烷烃三甲基铵乙烯基苯甲酸盐（CnTVB）在二氧化硅表面的吸附行为。具有较长烃链的C18TVB变体在OR中产生了三阶段吸附等温线，而C16TVB表面活性剂显示出两阶段吸附等温线。这可以用C18碳链更大程度的疏水性来解释，即在任何进一步吸附发生之前，需要表面存在显著更高浓度的表面活性剂。观察到两种表面活性剂的吸附速率均与浓度有关，C18TVB的吸附速率更快。OR数据表明，每种表面活性剂都可以通过水流完全从OR池中冲洗掉。而QCM数据未观察到这种情况，在QCM数据中仅看到部分冲洗掉。两种技术之间的差异据推测是由于QCM能够检测界面和本体行为，从而使吸附数据的解释变得复杂。
