Some remarks on excluded volume and on intrinsic viscosity plots

A simple (2, 2) Padé approximant based on the first three terms in the asymptotic cluster series for the expansion factor α2(z) is shown to give fairly good values over the entire positive range of the interaction parameter z. In a separate discussion it is shown by a specific example that extrapolations of viscosity data in good solvents and based on excluded-volume relations for flexible chains must be used only with great caution.