Enthalpy of mixing of poly(2,6-dimethyl phenylene oxide) and polystyrene

Various compatibility criteria for polymer-polymer blends are considered and their shortcomings discussed. An unambiguous thermodynamic criteria of compatibility, the enthalpy of mixing ΔHm, is obtained by application of Hess’s law to heat-of-solution data for blends and their components. The enthalpy of mixing for PPO/PS blends is determined by utilizing the Hess’s-law approach. Consideration is given to the excess glass enthalpy contribution to ΔHm. Consistent with the known compatibility of PPO/PS blends, a small negative ΔHm is found for all blend compositions.