Viscoeîastic properties of polyelevtrolyte solutions

Viscoelastic properties of poiyelectrolyte solutions were studied in the absence and presence of added salt over a wide range of polymer concentration in comparison with those of non-ionic polymers in good solvents. In the semidilute region where the polymer concentration C is higher than the overlap concentration for viscosity C*, but lower than C** (ca, 0.3 kg/dm3), the polymer concentration dependence of specific viscosity at zeroshear rate 77, increases with increasing added-salt concentration C5 and at high C_s it almost agrees with that of non-ionic polymers in good solvents. In the concentrated and entangled region where OCJ and C>C* more steeply increases with C even in salt-free solutions, implying the screening of electrostatic interaction and the increase of local fractional coefficients as considered in concentrated non-ionic polymer solutions. In the dilute region where C is lower than the overlap concentration for steady-state compliance C*, the steady-state compliance J_e more strongly depends on molecular weight and C than in non-ionic polymer solutions. In the semidilute region where C> CJ, but C<C**, the polymer concentration dependence of J_e is lower than that of non-ionic polymer solutions. In the concentrated and entangled region where C>C* and C>C**, the polymer concentration dependence becomes similar to that of non-ionic polymer solutions. In the concentrated and non-entangled region where C<C* and OC**, the frequency dependences of storage and loss moduli are well explained by the modified Rouse model like non-ionic polymer systems in the same region. The experimental results in the semidilute region are well explained by our theory of viscoelastic properties of polyelectroiyte solutions based on the reptation model with electrostatic interactions.