Interaction energies for each of the binary pairs PS/Pa-MS, PS/PMMA, and PMMA/Pa-MS were calculated by fitting spinodal curves predicted by the Flory-Huggins theory and the Sanchez-Lacombe equation of state theory to experimental cloud point data for blends of low molecular weight polymers. For blends of PS and -MS, where cloud points could not be observed, the molecular weight limit of miscibility was used to bracket the interaction energy. Phase separation boundaries for this system were predicted to be caused by UCST-type behavior. Oligomeric blends of PMMA with PS showed UCST-type phase boundaries while blends of PMMA with -MS showed LCST-type boundaries. The mechanism of phase separation boundaries was found to stem from the differences between the characteristic temperatures for the pure components (AT*). End groups on the oligomeric homopolymers significantly affect the calculated interaction energies, and corrections for this were made by three methods including a binary interaction model analysis.

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SYNOPSISThe interaction energies between PS, Pa-MS, and PMMA with several bisphenol-A-based polycarbonates were quantitatively determined from oligomer/oligomer, oligomer/ homopolymer, and homopolymer/copolymer blends. Interaction energies were calculated from the Flory-Huggins theory and the Sanchez-Lacombe equation of state theory using experimental cloud points or miscibility boundaries. Alkyl addition to the phenyl rings of polycarbonate is favorable for miscibility with polystyrene whereas halogenation of the bisphenol connector unit is favorable for miscibility with poly ( methyl methacrylate). Interaction energies are quantitatively ranked and described qualitatively in terms of changes in the electronic charge distribution of the polymer repeat units as calculated by SYBYL software.

SYNOPSISThe interaction energies between PS, Pa-MS, and PMMA, as well as acrylonitrile and maleic anhydride units, with a series of polysulfones were quantitatively determined from oligomer/oligomer, oligomer/ homopolymer, and homopolymer/copolymer blends. Interaction energies were calculated from the Flory-Huggins theory and the Sanchez-Lacombe equation of state theory using experimental cloud points or miscibility boundaries. Alkyl addition to the phenyl rings of polysulfone is favorable for miscibility with polystyrene whereas halogenation of the bisphenol connector unit favors miscibility with poly (methyl methacrylate). Interaction energies are quantitatively ranked and described qualitatively in terms of changes in the electronic charge distribution of the polymer repeat units as calculated by SYBYL software. 0 1994 John Wiley & Sons, Inc. Keywords: polysulfones styrene methyl methacrylate a-methyl styrene acrylonitrile blends interaction energies * Current address: The Dow Chemical Co., Midland, MI 48674. a Comments: 1. Pure component TB)s are too similar to be resolved. 2. Appearance depends on temperature. 3. Shows LCST behavior hut not at equilibrium. 4. Blend shows partial miscibility. 5. T, behavior depends on first or second heat to 250°C in DSC. 6. Appearance depends on composition. 7. T, behavior depends on first or second heat to 300°C in DSC. 8. T, behavior depends on first or second heat to 200°C in DSC. 9. Blends become cloudy once above T,.