EFFECTIVE-(CHI) IN A LATTICE THEORY OF MIXTURES

Using general thermodynamic arguments for an incompressible lattice sy stem, we demonstrate that the effective chi must be a complicated func tion of temperature, composition, polymerization indices, and the coor dination number of the lattice, even though the bare chi is merely a p arameter. We go beyond the random mixing approximation and present a l attice theory of mixtures which yields an effective chi consistent wit h experiments.