Theoretical equation of state of polymer blends: The poly(2,6-dimethyl-1,4-phenylene ether)–polystyrene pair

A recent theory of multicomponent fluids is applied for the first time to a compatible binary polymer blend. Good accord between the experimental pressure-volume-temperature measurements over the whole range of compositions by Zoller and theoretical predictions obtains. In particular, satisfactory predictions of high pressure from low-pressure information result. From the interplay between experiment and theory, the scaling quantities and thus the characteristic self- and cross interaction parameters are derived. The excess volumes are discussed and estimates of excess enthalpies presented. The theory predicts the actual enthalpy of the components or mixtures once the scaling parameters have been determined by means of volume-temperature data at atmospheric pressure. Enthalpy measurements to test these predictions are highly desirable.