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 () scales with polymer concentration () as ∼ , consistent with other natural polymers. In EMImAc, both polysaccharides form viscoelastic liquids, exhibiting ∼ , as expected for semiflexible polymer solutions. However, the terminal relaxation time, τ, and the specific viscosity, η, scale as τ ∼ and η ∼ , 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.