Dilute solution and rheological properties of hyperbranched polysaccharide from Pleurotus tuber-regium sclerotia

The dilute solution properties, critical coil overlap concentration, and rheological properties of the hyperbranched PTM3b polysaccharide were studied and compared. Flory factor (Phi) values of PTM3b in different solvents were smaller than those of linear chains as a result of the hyperbranched structure and wide polydispersity index. The relationships of 'zero shear' specific viscosity (eta(sp,0)) and coil overlap parameter (c[eta]) were represented as eta(sp,0 alpha)c(1.05 +/- 0.03), eta(sp,0 alpha)c(1.45 +/- 0.03) and eta(sp,0)alpha c(2.89 +/- 0.11) for the dilute, semi-dilute, and concentrated solution regions of PTM3b in 0.15 M aqueous NaCl, and coil overlap parameters were c*[eta] = 0.07 and c**[eta] = 0.29. Shear-thinning behavior was observed for PTM3b in 0.15 M aqueous NaCl in high concentration region, whereas Newtonian behavior in relatively low concentration region. The slope values of 2.34 and 12.8 were obtained from the double logarithmic plot of eta(0) versus c for PTM3b in 0.15 M aqueous NaCl. The slope value of 12.8 suggested that the hyperbranched polysaccharide resembled incompressible coils in the higher concentrated region. This work could provide some valuable and fundamental information to further understand the natural hyperbranched polysaccharide solutions from dilute to concentrated regions. (C) 2011 Elsevier Ltd. All rights reserved.