Rheological Properties of Concentrated Solutions of a Branched Polysaccharide Dextran in an Ionic Liquid

Abstract

Rheological properties of dextran solutions in 1-butyl-3-methylimidazolium acetate were examined up to the concentration (c) of 4.1 × 10 2 kgm −3. A high molecular weight (≈ 2 × 10 6) dextran with a degree of divergence of 4 % was used. The zero-shear viscosity estimated from the flow behavior indicated that dextran chains in the solutions entangle each other at c ≥ 1.7 × 10 2 kgm −3. In fact the plateau modulus (G 0 N) was obtained from the G′ and G″ curves for c ≥ 2.6 × 10 2 kgm −3. However, the anomalous results were obtained regarding entanglement of dextran chains: The molecular weight between entanglements was constant against c at 2.3 × 10 4 , so that a large number of entanglements per chain was expected in spite of the subtle rubbery plateau that was actually observed. It was proposed that the dextran has the main structure of long branches and each branch is densely sub-branched.

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

“…Although the data points are scattered in the low  region due to the low c, actually 1.0  10 1 and 3.0  10 1 kgm 3 , and the low viscosity thereby, the zero-shear viscosity (0) has been determined as the constant  observed in the rather high  10) . In this context it is expected that there exists the entanglement coupling between SPS chains in the solutions and therefore the rubbery plateau region appears in the dynamic viscoelasticity above cc.…”