Ellipsoid model for polyelectrolytes

The expansion factor of polyelectrolytes is calculated by using an equivalent ellipsoid model which is essentially the same as that used by Kurata, Stockmayer, and Roig in the theory of excluded volume effect of non‐ionic polymers. The Donnan‐Kimball approximate solution of the Poisson‐Boltzmann equation is used for evaluating the electric free energy of a chain. The result h applied to the calculation of the intrinsic viscosity [η] as a function of the molecular weight M and salt concentration ρ s , As a consequence, [η] is predicted to be expressible in the form over a wide range of the variables. Here K , B n and Φ 0 are constant independent of M and P s . In a limited range of large p s values, for example 0.1 ∼ 1 mole 1. −1 for a 1:1 added salt, the parameter B e (P s ) is proportional to P s −1 ; but in the range of lower value, of P s , for example 0.005 ∼ 0.1 mole 1. −1 , B e (p s ) becomes proportional to a lower inverse power of p s . For still lower values of p s , the above equation is no longer valid, because B e (P s ) becomes a function of M rather than of p s , In this range, the polyelectro‐lyte chain is in an extended rodlike form.