On the relationship between K and a and between Kθ and the molecular weight per chain atom

It is shown that in [η] = KMa there exists a relationship between K and a of the form log K = C − Ba. The parameters C and B are typical of each polymer and, under θ conditions, define a characteristic Kθ for the polymer. When plotted against m0/z, the molecular weight per backbone atom, the values of log Kθ cluster along three distinct lines. In a fashion similar to the observed dependence of number of atoms between chain entanglements on m0/z, the lines are associated with highly flexible polymers, intermediate flexibility polymers, and stiff chain polymers. Deviations from the intermediate flexibility line are explained on the basis of changes in the distribution of mass in the plane perpendicular to the overall direction of the backbone chain.