Thermodynamic miscibility of polystyrene–poly(2,6-dimethyl-1,4-phenylene oxide) blends

Abstract

Inverse gas chromatography was used to investigate the miscibility behaviour of molten polystyrene–poly(2,6-dimethyl-1,4-phenylene oxide) blends as a function of composition (0, 25, 50, 75, 85, and 100 wt.% PS). Specific retention volumes were measured for various solutes in pure and mixed stationary phases of these polymers at 240 °C. Infinite dilution weight fraction activity coefficients and Flory–Huggins polymer–solute (χ) and polymer–polymer (χ23′) interaction parameters were derived from these data.Negative polymer–polymer interaction parameters were obtained for blends containing more than 60 wt.% PS, suggesting strong intermolecular interactions in the molten state. This is in accord with the well-known compatibility of PS–PPO blends. However, positive χ23′ values were observed for blends containing less than 60 wt.% PS. This suggests weak intermolecular interactions, and perhaps some microheterogeneity in PS–PPO blends with a low PS content. In view of the single, composition dependent Tg measured for each of these blends the microheterogeneity or microphase separation must be on a finer scale than that measured by the glass transition.