MISCIBILITIES IN BINARY COPOLYMER SYSTEMS

A lattice theory is presented for liquid-liquid equilibria in binary s ystems containing random copolymers. This theory takes into account de viations from random mixing through a non-randomness factor which foll ows from a generalization of Monte-Carlo calculations for the three-di mensional Ising model. While the lattice remains incompressible, the e ffect of specific interactions (hydrogen bonding) is introduced by sup erimposing on the non-random (Ising model) expression for the Helmholt z energy of mixing a correction based on the lattice-gas model by ten Brinke and Karasz. The resulting theory can predict immiscibility caus ed by lower critical solution temperatures. Several theoretical miscib ility maps at fixed temperature were computed; these are compared with those predicted by the random-mixing Flory-Huggins theory. Theoretica l miscibility maps are also compared with experiment for a few systems with strong specific interactions.