Crossover behavior in the viscosity of semiflexible polymers: Solutions of sodium hyaluronate as a function of concentration, molecular weight, and temperature

Viscometric data on moderately concentrated solutions of the semiflexible macromolecule sodium hyaluronate over a range of molecular weight M and solute concentration c in aqueous 0.1M NaCl are analyzed using a generalized expression for the viscosity of isotropic polymers and their solutions. Owing to its semiflexible nature, the effects of excluded volume interactions are effectively screened for sodium hyaluronate under the conditions studied, and intramolecular hydrodynamic interactions are largely screened, even at infinite dilution. The consequences of this for scaling of the viscosity relative of solutions of sodium hyaluronate with the parameters cη and cM is discussed. The dependence of the viscosity on cM is in accord with the generalized relation, and leads to an estimate for the persistence length in reasonable accord with that found by light scattering measurements on dilute solutions. The temperature dependence of the viscosity suggests that the dependence of the persistence length on temperature may be partially suppressed with increasing polymer concentration.