Scaling Laws in Polysaccharide Rheology: Comparative Analysis of Water and Ionic Liquid Systems.

This study investigates the rheological behavior of two plant-based polysaccharides, with different degrees of hydrophilicity, agar (highly hydrophilic) and guar gum (hydrophilic), in water and 1-ethyl-3-methylimidazolium acetate (EMImAc). The rheological response of these polymers is highly dependent on the solvent's ability to disrupt intermolecular associations. In water, agar forms hydrogels, while guar gum behaves as a viscoelastic liquid with slow modes. The plateau modulus ( G N 0 ) scales with polymer concentration ( c ) as G N 0 ∼ c 3 , consistent with other natural polymers. In EMImAc, both polysaccharides form viscoelastic liquids, exhibiting G N 0 ∼ c 2.3 , as expected for semiflexible polymer solutions. However, the terminal relaxation time, τ D , and the specific viscosity, η sp , scale as τ D ∼ c 5.3 and η sp ∼ c 7.6 , indicative of intermolecular chain-chain associations. Despite the solvent or polysaccharide, the fractional viscosity overshoot and the shear strain at the maximum stress show a terminal Weissenberg number dependence similar to other synthetic polymers.