Hydrodynamic and conformational characterization of aqueous sodium alginate solutions with varying salinity.

Insight into the role of electrostatic interactions on the hydrodynamics and conformation of aqueous sodium alginate was gained through viscometry. Alginate chains are found to shrink in salt-free solutions more rapidly with increasing polymer concentration compared to salt-solutions. For salt-free solutions, a reduced polymer concentration of less than 1 suffices to make the alginate coil volume half of that at infinite dilution which becomes invariant when the reduced concentration exceeds 8. In saline media having salt concentration greater than 0.1 mol·L, the chains become more flexible, caused by the shielding of intra-chain repulsions. The chains effectively reached unperturbed state when the added salt concentration becomes ≥0.5 mol·L. Alginate chains are shown to remain stiff up to about 8-10 monomers within the investigated temperature range. This study explores the possible modification of the individual chain behavior induced by the neighboring chains or by the variation of temperature.