TOPOLOGICAL EFFECTS ON BLEND MISCIBILITY

The thermodynamics of mixing is shown to be quite sensitive to changes in the topology of blend components. Cyclic Bisphenol A carbonate oli gomers are miscible with a wider range of polystyrene (PS) molecular w eights than are chemically equivalent linear oligomers. The Flory-Hugg ins meanfield theory predicts the shape of phase boundaries quite well for linear PS/linear polycarbonate (PC) blends as well as for linear PS/cyclic PC blends. However, the interaction parameter is strongly de pendent upon topology with chi PS1/PCC < chi PSI/PCL. This result is e xplained in terms of a topological repulsion between rings, which is e xpected to be quite general.