Salt effect on the viscosity of semidilute polyelectrolyte solutions of NaPSS

We elucidate properties of aqueous solutions of sodium polystyrene sulfonate (NaPSS) by analyzing solution viscosity as a function of polymer and salt concentrations in the framework of the scaling model. This approach is based on a scaling relationship between solution correlation length ξ=lg^ν/B and number g of monomers per correlation volume for chains with monomer projection length l. The specific values B_pe, B_g, B_th, and of the B-parameter corresponding to exponents ν =1, 0.588, and 0.5 are determined by the fraction of charged monomers and their degree of ionization, the effective solvent quality for the polymer backbone and the chain Kuhn length. The values of the B-parameters were obtained from the plateaus of normalized specific viscosity η_sp/N_w(cl³)^1/(3v-1) as a function of the monomer concentration c for polyelectrolytes with weight average degree of polymerization, N_w. This information was used to construct a diagram of different solution regimes, calculate the fraction of free counterions, and the energy of the electrostatic blobs. By extending a scaling approach to entangled solutions, we determine the packing number for chain of corelation blobs and established crossover concentration to the entangled solution regime.