胶束溶液增溶过程的高分辩NMR研究

本文用高分辨~1H-NMR谱, 研究了十二烷基硫酸钠(SDS)胶束水溶液对m-二甲苯和苯甲醇的增溶作用。结果表明, 增溶物浓度很低时, m-二甲苯和苯甲醇均吸附在胶束-水“界面”。随着浓度增加m-二甲苯增溶在胶束的“栅栏”层和内核中, 并沿SDS的烃链均匀分布。当浓度约为0.34摩尔分数时, 它沿烃链的增溶达到“饱和”, 开始进入胶束内核中心。苯甲醇主要增溶在“栅栏”层中, 其羟基靠近胶束-水“界面”, 苯基深入到与α-CH_2基相邻的五个亚甲基的位置。

HIGH RESOLUTION NMR STUDIES OF THE SOLUBILISED PROCESS OF MICELLAR SOLUTION

This investigation is related to solubilisation process of aqueous micellar solu- tion containing nonpolar m-xylene or moderately polar benzyl alcohol and surfac- tant sodium dodecyl sulfate (SDS) by high resolution proton nuclear magnetic resonance spectroscopy (~1H-NMR). The examined results indicate that the long chain methylene in SDS shows a singlet signal for m-xylene/SDS/H_2O system,while it is split into an up-field signal and a down-field signal for benzyl alcohol/SDS/H_2O system. From the de- pendence of chemical shifts of SDS on solubilisate concentration, it is ascertained that at low solubilisate contents m-xylene or benzyl alcohol is solubilised by adsorption at the micelle-water “interface”. With further addition of m-xylene, it is solubilised and uniformly distributed along the hybrocarbon chain of surfactant. When mole fraction of m-xylene in surfactant is about 0.34, m-xylene goes predominantly the hydrocarbon chain of hte surfactant molecules. Whereas, benzyl alcohol solubilisation is probably localized in the palisade layer. It is orientated in such a manner ring is directed towarde the micellar interior. When a benzyl alcohol content approximates to 0.77 mole fraction, benzyl alcohol may go predominantly to the centre of the micellar interior core.The above-mentioned results are also discussed theoretically in this paper.