Flow behavior and linear viscoelasticity of cellulose 1-allyl-3-methylimidazolium formate solutions

The rheological properties of α-cellulose 1-allyl-3-methylimidazolium formate solutions were investigated using shear viscosity and dynamic rheological measurements in a large range of concentrations (0.1-10 wt%) at 25 °C. In steady shear measurement, the overlap concentration (c*) and the entanglement concentration (c(e)) were determined to be 0.5 and 2.0 wt% respectively, and the exponents of the specific viscosity (η(sp)) versus the concentration (c) were determined as 1.0, 2.0 and 4.7 for dilute, semidilute unentangled and entangled regimes respectively, which were in accordance with the scaling prediction for neutral polymer in θ solvent. The slopes of the relaxation time (τ) against the concentration for semidilute unentangled and entangled regimes were observed as 1.0 and 2.5 respectively. In dilute and semidilute unentangled regimes, failure of the Cox-Merz rule with steady shear viscosity larger than complex viscosity was observed; while the deviation from the Cox-Merz rule disappeared in semidilute entangled regime.