Viscoelasticity of Concentrated Solutions of Water-Soluble Polysaccharide Extracted from Soybean

Abstract

Dynamic viscoelasticity measurement was carried out for dilute and concentrated solutions of a water-soluble polysaccharide (SPS) extracted from soybean. The SPS solutions were able to be prepared up to the SPS concentration (c) of 30 wt% by using an ionic liquid 1-butyl-3-methylimidazolium acetate (BmimAc) as a solvent, while this “water-soluble” polysaccharide was actually soluble in water up to 3 wt%. The obtained dynamic viscoelasticity showed no rubbery plateau region, indicating that there was no entanglement coupling between SPS chains in the solutions. On the other hand, the c-dependence of the relative viscosity for the SPS solutions exhibited the critical concentration (c_c) of ca. 9 wt% which in general corresponds to the onset of entanglement coupling between polymer chains in the solutions. The anomalous absence of the entanglement coupling in the SPS solutions above c_c was attributed to the branching structure of SPS.