Scaling Laws\nin Polysaccharide Rheology: Comparative\nAnalysis of Water and Ionic Liquid Systems

This study investigates\nthe rheological behavior of two\nplant-based\npolysaccharides, with different degrees of hydrophilicity, agar (highly\nhydrophilic) and guar gum (hydrophilic), in water and 1-ethyl-3-methylimidazolium\nacetate (EMImAc). The rheological response of these polymers is highly\ndependent on the solvent’s ability to disrupt intermolecular\nassociations. In water, agar forms hydrogels, while guar gum behaves\nas a viscoelastic liquid with slow modes. The plateau modulus (<i>G</i><sub>N</sub><sup>0</sup>) scales with polymer concentration\n(<i>c</i>) as <i>G</i><sub>N</sub><sup>0</sup> ∼ <i>c</i><sup>3</sup>, consistent with other natural\npolymers. In EMImAc, both polysaccharides form viscoelastic liquids,\nexhibiting <i>G</i><sub>N</sub><sup>0</sup> ∼ <i>c</i><sup>2.3</sup>, as expected for semiflexible polymer solutions.\nHowever, the terminal relaxation time, τ<sub>D</sub>, and the\nspecific viscosity, η<sub>sp</sub>, scale as τ<sub>D</sub> ∼ <i>c</i><sup>5.3</sup> and η<sub>sp</sub> ∼ <i>c</i><sup>7.6</sup>, indicative of intermolecular\nchain–chain associations. Despite the solvent or polysaccharide,\nthe fractional viscosity overshoot and the shear strain at the maximum\nstress show a terminal Weissenberg number dependence similar to other\nsynthetic polymers.