LAUSR

Oscillatory and steady shear of cellulose in 1-ethyl-3-methylimidazolium methylphosphonate {[EMIm][P(OCH3)(H)O2]} were studied for cellulose concentrations from 0.017 to 10 wt. %, spanning the dilute, semidilute unentangled and entangled regimes. The overlap concentration of our cellulose in [EMIm][P(OCH3)(H)O2] is 0.065 wt. % and the entanglement concentration is 8× larger (0.5 wt. %). The concentration dependences of specific viscosity, relaxation time, and terminal modulus suggest that [EMIm][P(OCH3)(H)O2] is a good solvent for cellulose. Compared with the cellulose/1-butyl-3-methyl imidazolium chloride ([BMIm]Cl) system, this native cellulose in [EMIm][P(OCH3)(H)O2] has lower c* and ce, and much higher extent of entanglement. A significantly wider than expected rubbery plateau for the entangled solutions and failure of the Cox–Merz rule suggest that cellulose in [EMIm][P(OCH3)(H)O2] is not simply a flexible polymer in a good solvent. The relaxation mode distribution in the terminal regime is much broader for cellulose in [EMIm][P(OCH3)(H)O2] compared with the same cellulose in [BMIm]Cl. The delocalized phosphonate anion likely binds to hydroxyl groups on multiple cellulose chains, acting as temporary crosslinks.Oscillatory and steady shear of cellulose in 1-ethyl-3-methylimidazolium methylphosphonate {[EMIm][P(OCH3)(H)O2]} were studied for cellulose concentrations from 0.017 to 10 wt. %, spanning the dilute, semidilute unentangled and entangled regimes. The overlap concentration of our cellulose in [EMIm][P(OCH3)(H)O2] is 0.065 wt. % and the entanglement concentration is 8× larger (0.5 wt. %). The concentration dependences of specific viscosity, relaxation time, and terminal modulus suggest that [EMIm][P(OCH3)(H)O2] is a good solvent for cellulose. Compared with the cellulose/1-butyl-3-methyl imidazolium chloride ([BMIm]Cl) system, this native cellulose in [EMIm][P(OCH3)(H)O2] has lower c* and ce, and much higher extent of entanglement. A significantly wider than expected rubbery plateau for the entangled solutions and failure of the Cox–Merz rule suggest that cellulose in [EMIm][P(OCH3)(H)O2] is not simply a flexible polymer in a good solvent. The relaxation mode distribution in the terminal regime is much broa...