Solvent effects on sol-gel transition of alginate solutions by addition of cupric ions Original Research Article

Polyelectrolyte concentration dependence of critical exponents and gel points induced by addition of cupric ions to alginate solutions has been examined experimentally. Solvent effects have been taken into account when the gelation process is considered as the percolation of blobs. The critical exponents of relative viscosity, ϰ, are found to be in the range of 1.14–1.32, showing only a slight dependence on alginate concentration. The ϰ values are in good agreement with the prediction of Rouse clusters of percolation theory in which the hydrodynamic interaction is ignored in calculating the viscosity. A power-law relation has been found between the gelation point, φc, and alginate concentration C with an exponent of −0.70±0.05. Concentration dependence of gel point shows that the experimental results can be explained by a combination of scaling theories developed for vulcanization processes and polyelectrolytes in semi-dilute solutions. Based on the scaling analysis, good agreement has been obtained between the experimental exponent, −0.70±0.05, and theoretical exponents, −0.625 and −0.75, for semi-dilute polyelectrolyte solutions without and in the presence of an added salt, respectively.