NMR IN COLLOID SCIENCE WITH SPECIAL EMPHASIS ON SELF-AGGREGATING SYSTEMS

摘要

Fluids used in many processes of industrial or biological relevance often have a complex structure on the colloidal length scale. They may contain polymers, which may interact to form gels, self-assembled surfactant aggregates or two separate fluid phases such as in an emulsion. The structure on the colloidal length scale is often decisive in determining how a certain fluid performs in a specific application. As a consequence, much effort has been devoted to developing methods whereby structural studies of such complex fluids can be investigated. In the field of colloidal science, such fluids go under a number of different names; e.g. complex fluids, soft-matter, and microstructured fluids. NMR has been, together with different scattering methods, perhaps the most useful tool in structural studies of such complex fluids. In particular, two methods have been used: NMR relaxometry and diffusometry. While the former method relies on rather complicated modeling to extract the relevant information from the measured relaxation times, the latter method conveys easily interpretable information. It should be noted that both relaxometry and diffusometry measure dynamical quantities (relaxation rates and diffusion coefficients). As a consequence, the extraction of structural information from the observable quantities relies on modeling. In fact, there is often an intricate coupling between structure and dynamics in complex fluids, the details of which are often decisive in technical applications. Dissolution of solid polymers and drying of paint are two examples. This contribution will deal with the application of NMR diffusometry, and we will attempt to show how this method can be used in studies of complex fluids.