Phase behaviors of symmetric polymer blend systems

The modified double‐lattice model is extended to polymer blend systems. We redefine Cγ as a new universal function of interaction energy to reduce the mathematical defects that originate from the truncation of higher order interaction energy terms. We correlate Cγ with Ryu et al.'s numerical results for symmetric polymer blends with various chain lengths (r1 = r2 = 8, 20, 50, or 100). In addition, oriented interactions between polymer segments are considered with respect to the secondary lattice concept. The proposed model shows a good agreement with the experimental data. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1532–1538, 2004