Insight of the viscometric behavior of pullulan and curdlan derivative solutions: Effect of the nature and salt concentration

Increasing interest for polysaccharides investigation is based on their friendly behavior with environment and living organisms. The chemical structure, molar mass, chain conformation adopted in different media plays an important role for their performances in various practical applications. In this context, the viscometric behavior of two cationic pullulan and curdlan derivatives has been followed in water and salt solutions. The biopolyelectrolytes contain trimethylammonium propyl carbamate groups and trimethyl-N-(2-hydroxypropyl) ammonium ones attached to the backbone of pullulan and curdlan, respectively. The viscosity data have been interpreted in terms of the Wolf model. From the estimated values of the hydrodynamic parameters expressed by intrinsic viscosity [eta], the hydrodynamic interaction parameter (b), etc., the dependence of the polyion conformation on the polyelectrolyte concentration and salt nature and concentration has been revealed; [eta] decreased and b increased with increasing salt concentration and counterions valence. The viscosity data obtained in salt solutions allowed the estimation of the stiffness parameter (B), the expansion factors for the viscosity (alpha eta) and for the root mean-square radius of gyration, alpha S, etc. and the establishment of counterions binding type as an "atmospheric ionic" one for the mononovalent counterions.