Progress in nuclear magnetic resonance studies of surfactant systems

Nuclear magnetic resonance (NMR), as a powerful technology, is widely used to characterize the physicochemical properties of surfactants in solution. As a sensitive technique to molecular environment, NMR is beyond the reach of other spectral methods in surfactant systems. Recent years, intensive investigations of surfactants by NMR were reported but not well summarized; therefore, we highlight these significant progresses, which may shed light on the challenges to understand their behavior and mechanisms in surfactant systems. The theory of various NMR methods was introduced, including chemical shifts, diffusion, relaxation, 2D nuclear Overhauser effect spectroscopy and rotating frame nuclear Overhauser effect spectroscopy. The behavior, interaction, and mechanisms among surfactants and other molecules from NMR technologies were discussed. Challenges to understand the behavior and mechanisms in surfactant systems and instrumentation limits are addressed as perspectives.