Calorimetry was used to gain insight into the thermodynamics of mixing of unlike species, designed to represent organic polymers. These results are to be useful in predicting miscibility between various polymers and poly(arylene sulfides). Phenyl sulfide (PS) and phenyl disulfide (PSS) were used as models for poly (phenylene sulfide) (PPS) and were mixed with model compounds that are representative of other polymer classes. The enthalpy of mixing was measured for a large number of combinations. The results are interpreted in terms of a summation of the effects of specific interactions and dispersive forces. It is seen from these data that the presence of aromatic side groups enhances the miscibility of the species with the poly (phenylene sulfide) model compound. Furthermore, exothermic heats of mixing were observed between the PPS model and compounds that contain carbonyl, amide, or amine moieties. Finally, the sulfur atom in PPS seems to play only a minor role in determining its interactions with other species. Replacing sulfur with oxygen (or even an alkyl group) is seen to have very little effect on the heats of mixing results.