In this work, we applied a novel pulsed field gradient (PFG) NMR option, which combines advantages of high-field (17.6 T) NMR and high magnetic field gradients (up to 30 T/m), to study diffusion of anions, cations and water in two 1-ethyl-3-methylimidazolium-based ionic liquids. Application of high field allows for an easy recording of an NMR signal from small amounts of water added to the ionic liquids. Using high gradients is advantageous because under conditions of such gradients any susceptibility-induced inhomogeneities in the local magnetic field are expected to be negligibly small in comparison with the applied gradients. PFG NMR studies have been performed in a broad range of temperatures and for different diffusion times. The effect of water addition on the diffusion behavior of the anions and cations is discussed in the context of the presence of polar and nonpolar domains in the ionic liquids. A partial screening of the electrostatic interaction between the cations and anions in the polar domains by water is believed to be responsible for the following changes in the diffusion behavior, which were observed experimentally: (i) increase in the ion diffusivities with increasing water concentration, and (ii) decrease in the difference between the diffusion coefficient of the cation and that of the anion as water concentration increases.

Proton pulsed field gradient (PFG) NMR was used to study the diffusion of poly(diallyldimethylammonium chloride) (PDADMAC) in coacervates formed from this polycation and the protein bovine serum albumin (BSA). Application of high (up to 30 T/m) magnetic field gradients in PFG NMR measurements allowed probing the diffusion of PDADMAC on a length scale of displacements as small as 100 nm in coacervates formed at different pH's and ionic strengths, i.e., conditions of varying protein-polycation interaction energy. Studies were carried out for a broad range of diffusion times and corresponding values of the mean square displacements. Several ensembles of PDADMAC polycations with different diffusivities were observed in the measured range of diffusion times. The existence of these ensembles and the pattern of their changes with increasing diffusion time support the hypothesis about the microscopic heterogeneity of PDADMAC-BSA coacervates and also provide evidence for the dynamic disintegration and reformation of dense domains.