New insights into viscosity abnormality of sodium alginate aqueous solution

The viscosities of dilute sodium alginate aqueous solutions have been measured at various temperatures. The upward bending phenomenon of the reduced viscosity of sodium alginate solution in the dilute concentration region resulted from the adsorption of polymer on the glass capillary wall. Experimental viscosity data satisfactorily coincided with the recent theory regarding the adsorption effect of polyelectrolyte. The theory predicted that the second term of reduced viscosity would vanish due to the presence of inter-chain Coulombic repulsion interaction, which prevents self-association or cluster formation in the experimental concentration regime. Furthermore, temperature dependence of the hydrodynamic diffusion constants of sodium alginate in aqueous solution was measured by dynamic light scattering (DLS). The morphologies of sodium alginate on the glass surface were also investigated by atomic force microscope (AFM). A self-consistent result was obtained quantitatively by different experimental means.