Four binary and two ternary experimental cloud point curves (CPC) for systems formulated with styrene (S), a dimethacrylate resin (DMAR), and poly(butadiene-co-acrylonitrile) liquid rubbers terminated in vinyl (VTBN) or carboxyl groups (CTBN), are presented. Measured CPCs of the binaries DMAR-CTBN, DMAR-VTBN and S-DMAR show upper critical solution temperature (UCST), while CPCs of the ternary S-DMAR-rubbers show liquid-liquid partial miscibility on the DMAR-rubber binary sides. A Flory-Huggins (F-H) thermodynamic analysis of the three measured binary cloud-point data allows the calculation of the respective interaction parameters and their temperature dependence. Interaction parameters for the other two binaries, S-CTBN (VTBN), were selected as the set of values that produced calculated spinodals, for the S-DMAR-rubbers ternaries, tangent to the respective experimental cloud-point diagrams at the critical point. The thermodynamic analysis was done taking into account the molecular polydispersity of CTBN, VTBN and DMAR components. Final morphologies of CTBN modified cured materials, obtained with two different molecular weight DMAR, were well correlated with the predicted miscibility for both systems.