Quasi-Elastic Neutron Scattering on Bimodal Dynamics in Molecular Solutions of Cellulose

Local dynamics in molecular solutions of cellulose have been studied using quasi-elastic neutron scattering on ternary mixtures of microcrystalline cellulose, ionic liquid 1-ethyl-3-methyl-imidazolium acetate, and cosolvent dimethylformamide. Two distinct dynamic behaviors in solutions have been identified, with slow dynamics likely attributed to long-range translational diffusion and fast dynamics likely involving the motion of IL in nanoaggregates. The presence of cellulose suppresses both dynamic modes as the residence time for both slow and fast dynamics increases, while the radius of confinement remains invariant upon cellulose dissolution. Arrhenius activation behaviors are followed generally; the activation energy decreases for fast dynamics upon cellulose dissolution while showing no measurable change for slow ones. This study offers new information about the dynamics of an important class of renewable biomaterials.