胶束溶液增溶过程的高分辩 NMR 研究

HIGH RESOLUTION NMR STUDIES OF THE SOLUBILISED PROCESS OF MICELLAR SOLUTION

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基相邻的五个亚甲基的位置。

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/HO system,while it is split into an up-field signal and a down-field signal for benzyl alcohol/SDS/HO 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 solu- bilised 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 to the centre of the micellar interior core,having“solubilised saturation”along the hydrocarbon chain of the surfactant molecules.Whereas,benzyl alcohol solubi- lisation is probably localized in the palisade layer.It is orientated in such a manner that the polar group is absorbed closely to the micellar surface and the aromatic 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.