关键词: 核磁共振, 弛豫时间, 自扩散, 表面活性剂, 化学位移

Abstract: Surfactant is a substance that lowers the surface tension of the medium in which it is dissolved. They form oriented colloidal aggregates, micelles, when a specific concentration is exceeded and abrupt changes in physical properties of the solution will be observed. Surfactant systems have been proved to be very useful in many biological and industrial processes. Properties of these systems have been intensively investigated by many spectroscopy methods, especially proton nuclear magnetic resonance (1H NMR). It has played more and more important role in the continued development of NMR new techniques. Characterization of micellization processes, physical properties of micelles, e.g. structure, size and shape, hydration of micelles, solubilization by micelles, interaction between micelles of different kinds of surfactants, and that with biological compounds and with polymers were studied by the existing sophisticated NMR techniques. These investigations demonstrate that NMR spectroscopy is a versatile technique for the study of surfactants. It provides information at a molecular level that is not available by other spectroscopic methods. Chemical shift changes, relaxation experiments and NMR self-diffusion measurements are almost used routinely. The use of two-dimensional NMR spectroscopy, 2D NOESY and HOESY is a growing trend in studying the chain packing in micelles as well as interactions between micelles with other molecules, biological and polymeric. These methods provide a deeper insight into the relative arrangement of surfactant molecules in an associated assembly.

Key words: NMR, Relaxation, Self-diffusion, Surfactant, Chemical shift