Andersson Martin, Råsmark Per Johan, Elvingson Christer, Hansson Per
Department of Pharmacy, Uppsala University, Box 580, S-75123 Uppsala, Sweden.
Langmuir. 2005 Apr 26;21(9):3773-81. doi: 10.1021/la047316v.
The binding of two cationic surfactants, dodecyltrimethylammonium bromide (DoTAB) and N-(1,1,2,2-tetrahydroperfluorodecanyl)pyridinium bromide (HFDePB), to covalently cross-linked sodium poly(styrenesulfonate) (PSS) microgels has been investigated by means of micromanipulator-assisted time-resolved light microscopy on single gels. It is demonstrated that repeated measurements on the same microgel under conditions of controlled liquid flow give highly reproducible results. The two surfactants are found to behave very differently with respect to degree of swelling, surfactant distribution in the gels, both during shrinking and at equilibrium, and kinetics of volume changes induced by them. The main difference is attributed to the presence of a hydrophobic interaction between PSS and the DoTAB micelles, absent in the case of HFDePB. Kinetic shrinking curves are recorded and analyzed using a model for steady-state transport of surfactant between the solution and the gels. Aggregation numbers for DoTAB in PSS solutions obtained from fluorescence quenching measurements are presented. A strong dependence on the surfactant-to-polyion concentration ratio is observed. Relations between surfactant binding isotherms, phase diagrams for linear polyelectrolyte/surfactant/water systems, and the binding to gels are discussed.
通过微操纵器辅助的单凝胶时间分辨光学显微镜，研究了两种阳离子表面活性剂，即十二烷基三甲基溴化铵（DoTAB）和N-（1,1,2,2-四氢全氟癸基）吡啶溴化物（HFDePB）与共价交联的聚苯乙烯磺酸钠（PSS）微凝胶的结合情况。结果表明，在受控液体流动条件下对同一微凝胶进行重复测量可得到高度可重复的结果。研究发现，这两种表面活性剂在溶胀程度、收缩过程中和平衡时凝胶中的表面活性剂分布以及由它们引起的体积变化动力学方面表现出非常不同的行为。主要差异归因于PSS与DoTAB胶束之间存在疏水相互作用，而HFDePB的情况则不存在这种相互作用。记录了动力学收缩曲线，并使用表面活性剂在溶液和凝胶之间稳态传输的模型进行分析。给出了通过荧光猝灭测量获得的PSS溶液中DoTAB的聚集数。观察到其对表面活性剂与聚离子浓度比有很强的依赖性。讨论了表面活性剂结合等温线、线性聚电解质/表面活性剂/水体系的相图以及与凝胶结合之间的关系。
