Quantitative description of the intrinsic viscosity of branched polyelectrolytes

A set of critically cross-linked polystyrenesulfonates with fractal geometry having molecular weights in the range 4.96 x 10(5) < M-w < 3.07 x 10(6) was prepared and characterized by viscometry in salt free aqueous solutions. Also these structures show the polyelectrolyte effect, which is a strong increase in reduced viscosity with decreasing concentration. Contrary to that in linear chains, the viscosity below the overlap concentration turned out to be molecular weight independent, which interestingly bridges the behavior between spheres and linear chains. A quantitative evaluation of the data on the basis of a recently decribed model of polyelectrolyte viscosity considering single particle and cooperative multiparticle effects of the charges on viscosity reveals that the complete dependence on polymer concentration is described by assuming only the effective charge number per polymer molecule, Z(eff). It is not necessary to assume any concentration-dependent conformational changes.