Characterization of viscoelastic properties of polyacrylamide/Cr(III) hydrogels

The viscoelastic properties of polyacrylamide/Cr(III) hydrogels were characterized with the help of oscillatory shear rheometer. The serrated-plate geometry rather than the cone-plate geometry was used in order to avoid the slip effect. The dynamic storage modulus (G') increased with increasing polyacrylamide and/or Cr(III) concentrations. The mean molecular weight of the chains adjoining adjacent crosslinks (Mc), calculated according to the elastic rubber theory, exhibited the same order of the primary polymer. G' decreased with increasing monovalent salt concentration, owing to the polyelectrolyte effect.