NMR Self-Diffusion Studies of Surfactant and Polymer Systems. Methodology and Applications

Abstract: The main focus of this thesis has been to explore how the PFG NMR technique for diffusion measurements can be used to obtain useful information from various systems. The investigated systems have one thing in common; they belong to the general field of surface and colloid chemistry. The thesis is divided in two parts: one section is a summary and the other section contains four publications from different scientific journals and, in addition, one manuscript. The first chapter in the summary treats the most important part of a gradient experiment, i.e., the gradient probe. Here, the aim is to explain how the gradient probe is constructed and also to discuss some additional problems regarding the equipment that one may encounter when doing PFG NMR diffusion experiments. In the second chapter, I introduce the PFG NMR concept and some of the theory behind these experiments. Finally, in the third chapter I summarize and discuss the findings of the papers. The influence of a nonconstant magnetic field gradient on PFG SE NMR diffusion experiments was investigated in paper I, by performing computer simulations. In paper II the technique has been used to investigate a nonionic surfactant (or rather an amphiphilic polymer)/water system, and in paper III the influence of a molecular weight distribution of polymers on PFG NMR measurements are considered. Paper IV and V are examples where the technique has been used in emulsion systems. Paper IV applies the technique to a double emulsion (water in oil in water emulsion), while paper V shows diffraction-like effects in a highly concentrated water in oil emulsion. The interpretation of the positions of the diffraction-like peaks in paper V convey structural information without the need of complicated mathematical modeling.