The properties of concentrations in a polymer blend

For the flexible polymer molecule the concepts of two concentrations, namely, segmental and molecular concentrations have been proposed in this paper. The former is equivalent to the volume fraction. The latter can be defined as the number of the gravity centers of macromolecules, or as the number of the chainheads per unit volume. The two concentrations should be correlated each other by the conformational function of the polymer chain and could be used in different thermodynamic equations. On the bases of these concepts it has been proved that the Flory-Huggins mixing entropy should be the result of the mixing 'ideal chainhead gases'. The general correlation between the mixing free energy and the scattering function (structural factor) of polymer blends has been studied based on the general thermodynamic fluctuation theory. When the Flory-Huggins mixing free energy was adopted, de Gennes scattering function of polymer blend can be derivated.EI0122-25