Copolymers of tribromostyrene (TBS) with styrene (S) and methyl methacrylate (MMA) were synthesized. The miscibility regions for blends of STBS copolymers with the homopolymers polystyrene (PS), poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), tetramethyl bisphenol A polycarbonate (TMPC), as well as blends of MMA-TBS copolymers with poly(methyl methacrylate) (PMMA) were determined. Blends of MMA-TBS copolymers with styrene-methyl methacrylate (SMMA) copolymers and blends of both TBS copolymers with styrene-acrylonitrile (SAN) and styrene-maleic anhydride (SMA) copolymers were also investigated. Interaction energies for monomer unit pairs were calculated from the isothermal miscibility maps using the Flory-Huggins theory combined with the binary interaction model. The experimental phase separation temperatures were found to be similar to the spinodal temperatures predicted from the lattice-fluid theory of Sanchez and Lacombe using these interaction energies. (C) 2000 Elsevier Science Ltd. All rights reserved.