DENSITY-TUNED POLYOLEFIN PHASE-EQUILIBRIA .1. BINARY-SOLUTIONS OF ALTERNATING POLY(ETHYLENE PROPYLENE) IN SUBCRITICAL AND SUPERCRITICAL PROPYLENE, 1-BUTENE, AND 1-HEXENE - EXPERIMENT AND FLORY-PATTERSON MODEL

Temperature-pressure phase boundaries are measured for solutions of alternating poly(ethylene-propylene) fractions in propylene, 1-butene, and 1-hexene. These amorphous fractions have similar structures and very narrow molecular weight distributions but differ in average molecular weight, from 0.79K to 96.4K. The phase transitions, typically in the form of a cloud-point transition, are determined in a variable-volume, optical cell up to 200-degrees-C and 550 bar. The phase transitions are found to be dependent on the difference in size (molecular weight) between polyolefin and solvent. When the difference is large enough, the LCST and UCST curves merge into one curve that we refer to as U-LCST. The LCST, UCST, and U-LCST curves are correlated with Flory-Patterson's corresponding states theory.