Impediments to the accurate structural characterisation of a highly concentrated emulsion studied using NMR diffusion diffraction

Pulsed gradient spin–echo (PGSE) NMR diffusion studies with subsequent analysis using the Gaussian phase distribution (GPD) approach have long been used to determine the structure of emulsions. With the increasing availability of spectrometers equipped with higher gradient strength generation capabilities it is possible to extend PGSE measurements to where diffusive diffraction effects become evident. However the GPD approach cannot predict these diffraction-like coherence features which can be a rich source of information. With appropriate modelling based on the short gradient pulse approximation (SGP) such coherence features can provide morphological characteristics such as pore size, tortuosity, and connectivity. Further, the deviation of coherence features from ideal cases can be used to elucidate additional features such as the polydispersity of emulsion droplets which is a fundamental and crucial physical characteristic that influences the emulsion stability, rheology, and functionality. In this study analysis of PGSE NMR diffusion diffraction coherence features using the multiple propagator matrix formalism extension of the SGP approach is used to study structural characteristics of a highly concentrated emulsion.

PGSE NMR diffusion diffraction can be a rich source of information for characterising emulsions, however, detailed consideration of the method and analysis is needed for correct data interpretation.Figure optionsDownload as PowerPoint slide