Revisiting the solution properties of sodium alginate in aqueous media

We conduct a comprehensive characterization study of two standard commercial sodium alginate (SA) samples in aqueous media over a wide range of experimental conditions. While the general viscometric features are basically not different from previous reports on aqueous SA solutions, corresponding dynamic light scattering and depolarized dynamic light scattering analyses reveal, for the first time, the dominance of highly uniform, micron-sized and slightly anisotropic oblate spheroids. The solutions are later used to produce uniform micron-fibers in thin films via a slow quenching (30 min) at 90 °C, with the fiber diameters matching those of the oblate colloids in pristine solutions. The van Gurp-Palmen plot of dynamic rheology data over a wide range of SA solutions with varying temperatures, concentrations, and molecular weights exhibits an excellent superposition and colloidal features. The present findings suggest that SA has the propensity to form dominantly colloidal clusters in aqueous media and, in particular, the capability to produce highly uniform self-assemblies from the solution to quenching state.