Phase behavior of binary mixtures of oligomeric styrene/allyl alcohol copolymers and aliphatic polyesters

The phase behavior of binary mixtures of copolymers containing varying amounts of styrene and allyl alcohol (SAA) with a wide range of aliphatic polyesters has been examined. All of the copolymers and most of the polyesters had low molecular weights in the oligomeric range; hence, entropy effects were a significant factor in the observed phase behavior. The polyesters employed had CH₂/COO ratios over the entire range from 2 to 12. The SAA copolymers were completely miscible with polyesters in the middle of this range based on the observation of a single composition-dependent glass transition for these mixtures. Upper critical solution temperature behavior was observed for blends of SAA copolymers with polyesters having ratios of CH₂/COO immediately on either side of this optimum region of Polyester structure. Complete immiscibility was noted for blends with polyesters having CH₂/COO ratios at either extremity of the range examined. Interaction parameters were deduced from either melting point depression data or the cloud point observations and correlated with the structure of the components.