Liquid-state NMR analysis of nanocelluloses

Recent developments in ionic liquid electrolytes for cellulose or biomass dissolution has also allowed for high-resolution 1H and 13C NMR on very high molecular weight cellulose. This permits the development of advanced liquid-state quantitative NMR methods for characterization of unsubstituted and low degree of substitution celluloses, for example, surface-modified nanocelluloses, which are insoluble in all molecular solvents. As such, we present the use of the tetrabutylphosphonium acetate ([P4444][OAc]):DMSO-d6 electrolyte in the 1D and 2D NMR characterization of poly(methyl methacrylate) (PMMA)-grafted cellulose nanocrystals (CNCs). PMMA-g-CNCs was chosen as a difficult model to study, to illustrate the potential of the technique. The chemical shift range of [P4444][OAc] is completely upfield of the cellulose backbone signals, avoiding signal overlap. In addition, application of diffusion-editing for 1H and HSQC was shown to be effective in the discrimination between PMMA polymer graft resonances and ...