Mixtures of 1-ethyl-3-methyl-imidazolium acetate ([C2mim][OAc]) and water across the entire composition range, from pure [C2mim][OAc] to pure water, have been investigated using density, viscosity, and NMR spectroscopy, relaxometry, and diffusion measurements. These results have been compared to ideal mixing laws for the microscopic data obtained from the NMR results and macroscopic data through the viscosity and density. It was also found that the mixing of the two fluids is exothermal. The proton spectra indicate though that [C2mim][OAc] and water are interacting without the formation of new compounds. The maximal deviations of experimental data from theoretical mixing rules were all found to occur within the range 0.74 ± 0.06 mol fraction of water, corresponding to approximately three water molecules per [C2mim][OAc] molecule.

Solutions of microcrystalline cellulose in 1-ethyl-3-methyl-imidazolium acetate have been investigated using pulsed-field gradient (1)H NMR. In all cases the geometrically larger cation was found to diffuse faster than the smaller anion. Arrhenius temperature analysis has been applied to the ion diffusivities giving activation energies. The diffusion and published viscosity data for these solutions were shown to follow the Stokes-Einstein relationship, giving hydrodynamic radii of 1.6 Å (cation) and 1.8 Å (anion). Theories for obstruction, free-volume and hydrodynamic effects on solvent diffusion have been applied. The Mackie-Meares and Maxwell-Fricke obstruction models provided a correct trend only when assuming a certain fraction of ions are bound to the polymer. From this fraction it was shown that the maximum dissolvable cellulose concentration is ∼27% w/w, which is consistent with the highest known prepared concentration of cellulose in this ionic liquid. The Phillies' hydrodynamic model is found to give the best description for the cellulose concentration dependence of the ion diffusivities.

The highly inhomogeneous distribution of collagen fibrils may have important effects on the biphasic mechanics of articular cartilage. However, the effect of the inhomogeneity of collagen fibrils has mainly been investigated using simplified three-layered models, which may have underestimated the effect of collagen fibrils by neglecting their realistic orientation. The aim of this study was to investigate the effect of the realistic orientation of collagen fibrils on the biphasic mechanics of articular cartilage. Five biphasic material models, each of which included a different level of complexity of fibril reinforcement, were solved using two different finite element software packages (Abaqus and FEBio). Model 1 considered the realistic orientation of fibrils, which was derived from diffusion tensor magnetic resonance images. The simplified three-layered orientation was used for Model 2. Models 3-5 were three control models. The realistic collagen orientations obtained in this study were consistent with the literature. Results from the two finite element implementations were in agreement for each of the conditions modelled. The comparison between the control models confirmed some functions of collagen fibrils. The comparison between Models 1 and 2 showed that the widely-used three-layered inhomogeneous model can produce similar fluid load support to the model including the realistic fibril orientation; however, an accurate prediction of the other mechanical parameters requires the inclusion of the realistic orientation of collagen fibrils.