The Third Virial Coefficient in Polymer Solutions

Abstract

With the aid of approximate models for the intermolecular potential energy, the third virial coefficient Γ₃ in the virial expansion for the osmotic pressure of a dilute polymer solution has been determined as a function of the second coefficient and one additional parameter obtainable from intrinsic viscosity or light scattering measurements. The theory and experimental results agree in indicating that the ratio Γ₃/Γ₂² for most solutions is markedly less than the value of ⅝ given by the hard sphere molecular model proposed by others for the estimation of Γ₃. The limitations are discussed under which light scattering may be used for evaluation of the virial coefficients.