DWS microrheology of a linear polysaccharide.

Abstract

Diffusing wave spectroscopy has been used to measure the rheological behavior of pullulan (Mw = 1 × 10^{5}) aqueous solutions up to concentration of 40 g/dL. It was found that these solutions were mainly viscous, with the loss modulus G‘‘ higher than the elastic modulus G‘. The plot of the specific viscosity ηsp as a function of pullulan concentration showed two critical concentrations c* = 4 g/dL and c** = 15 g/dL. For c < c*, η sp ≈ c^{1.25±0.05}; for c* < c < c**, η sp ≈ ^{c2±0.05}; and for c > c**, η sp ≈ c^{4.5±0.5}. These results are in very good agreement with those reported in the literature.