Non-Newtonian Intrinsic Viscosity of Coiled Chain Polymers. II. Molecular Expansions and Solvent Effect

A theory of the intrinsic viscosity of coiled chain polymers is presented on the basis of an equivalent ellipsoid model, by taking into account the effect of the excluded volume of polymers. A relation between the hydrodynamic expansion of a polymer and its excluded volume is obtained. It is found that the intrinsic viscosity decreases with the increase in shear rates, and that this tendency becomes pronounced with the increase in the molecular weight of the polymer and the power of the solvent used. This originates in the fact that the increase in the excluded volume gives rise to the increase in the fraction, of equivalent ellipsoids with large axial ratios. The results are compared with other theories and with experiments. The agreement between the theory and experimental data on polystyrene solutions is fairly good over the range from low to moderate shear rates.