Unique gelation and rheological properties of the cellulose/CO2-based reversible ionic liquid/DMSO solutions

Gelation and rheological behaviors of cellulose/CO 2 -based reversible ionic liquid (RIL)/DMSO solutions were investigated. The exponents of specific viscosity η sp versus concentration c were determined for wood pulp (WP) and microcrystalline cellulose (MCC) solutions. The complex viscosity acquired using oscillatory shear closely follows the steady shear viscosity, thus revealing the applicability of Cox-Merz rule. The influence of RIL content in the solvent on apparent viscosities, activation energy, intrinsic viscosities, specific viscosity-c[η] master curve, and relaxation time were also investigated. Gelation occurred in this cellulose solution system due to thermal-induced CO 2 release from the decomposition of the CO 2 -based reversible ionic liquid. The formed gel was stable in air, but re-dissolved when exposed to CO 2 , indicating the switch-on and switch-off effects of CO 2 in cellulose dissolution and gelation.