PHASE-BEHAVIOR OF POLY(ETHYLENE-1-BUTENE) IN SUBCRITICAL AND SUPERCRITICAL PROPANE - ETHYL BRANCHES REDUCE SEGMENT ENERGY AND ENHANCE MISCIBILITY

On the basis of experimental batch-cell data, increasing short-chain b ranch density is found to reduce the cloud-point pressure of poly(ethy lene-1-butene) solutions in propane, by as much as a factor of 3. This trend is captured by a SAFT approximation via an effective segment en ergy that depends on the branch density. Increasing branch density is found to decrease the effective segment energy and, hence, to make it closer to that of propane, which is consistent with the enhanced misci bility of branchy poly(ethylene-1-butenes) in propane.