MISCIBILITY AND IMMISCIBILITY IN FUNCTIONALIZED ASSOCIATING POLYMER SYSTEMS - POLYSTYRENE POLY(PHENYLENE OXIDE) BLENDS

The thermal properties of several families of polystyrene-poly(phenyle ne oxide), sulphonated polystyrene-poly(phenylene oxide), polystyrene- sulphonated poly(phenylene oxide), and sulphonated poly-styrene-sulpho nated poly(phenylene oxide) blends were studied by differential scanni ng calorimetry. The appearance of a single glass transition temperatur e, i.e. blend miscibility, depended on the level of sulphonation of on e or both components of the blend. Even though blends formed from the unfunctionalized components were miscible over the complete compositio n range, miscibility was reduced as the sulphonation level increased i n either component. A substantially broader range of miscibility was o bserved when both blend components were functionalized. Compared with blends containing one sulphonated component, where immiscibility could occur within a relatively modest sulphonation range (typically 2-4 mo l%), blends with two sulphonated components retained miscibility over a substantially broader sulphonation range (typically 10 mol%). The re sults are interpreted in terms of the mean field theory involving inte raction parameters for the individual monomer segments.