VISCOELASTIC PROPERTIES OF ALGINATE AQUEOUS-SOLUTIONS IN THE PRESENCE OF SALTS

The influence of added salts on the dynamic viscoelastic properties are investigated for aqueous solutions of alginates that have various molecular weights and mannuronate/guluronate (M/G) ratios. The dynamic moduli of the systems increase with increasing concentration of the added salt in the low‐frequency region. The effect is notable in the order of KCl < NaCl < MgCl2 ≪ CaCl2. The values of the dynamic moduli in the rubbery plateau are independent of the addition of the salts, irrespective of the M/G ratio of the alginate. These facts strongly suggest that the structure that is formed by the interaction between the alginates and the metal ions does not work as cross‐linking points but as heterogeneous relaxation units having a relatively long relaxation time from a rheological viewpoint. Copyright © 1990 John Wiley & Sons, Inc.