A survey of the phase behavior of blends of hydroxyphenyl-and acetoxyphenyl-terminated hyperbranched polyesters with linear polymers such as polycarbonate, polyesters, and polyamides was carried out. For comparison, blends of poly(acetoxystyrene) (PAS) and poly(vinylphenol) (PVPh) and pairwise combinations of these and the two hyperbranched polyesters were studied. The hydroxyterminated hyperbranched polyester blend miscibility was identical to that of poly(vinylphenol); this suggests that strong interactions due to hydrogen bonding, more so than chain architecture, dominate the blend miscibility. The acetoxy-terminated hyperbranched polyester showed less miscibility than those hydroxy-terminated polymers due to the absence of strong interactions but still more miscibility than the linear PAS. None of the blends of linear PVPh or PAS with hyperbranched polymer was miscible. However, homogeneous blends of PAS with PVPh and of the two hyperbranched polyesters were observed. In addition, a blend of linear Bisphenol A polycarbonate (PC) with an all-aromatic hyperbranched polyester resulted in increased tensile and compressive moduli and decreased strain-to-break and toughness compared to those of PC.

The storage (O') and loss (G") shear moduli of solutions of four polystyrenes with narrow-distribution weightaverage molecular weights (M) from 19,800 to 860,000 have been measured over a frequency range frpm 0.02 to 634 Hz. The solvents were two Aroclors (chlorinated diphenyls) with a viscosity range from 2 to 7000 P over a temperature range from -

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This high-resolution solid-state NMR work explores the usefulness of carbon-carbon nuclear spin diffusion to probe the miscibility of polymer blends. Experiments involving one-and two-dimensional NMR spectra, applied to blends ofpoly(ethylene terephthalate) (PET) and bisphenol-A polycarbonate (BP APC), show that spin exchange occurs between carbon-13 nuclei located in monomer units that belong to the two different homopolymers. Carbon spin diffusion, which strongly depends on the internuclear distance, is explored as a possible probe for specific interactions between polar groups of the two polymers. Our results clearly show that !he PET /BP APe blends studied are homogeneously mixed at distances of 4.5 to 6 A.

Variable-temperature 13C NMR spectra of bisphenol-A polycarbonate, isotopically labeled with 13C at the carbonyl position, have been analyzed in terms of local motion of the carbonate group. Slight variation of the observed powder pattern occurred as the temperature was varied from -255 "C to room temperature. Nevertheless, a computer analysis showed that oscillation about the chain axis through a total angle of 40" is consistent with the results. IntroductionBecause bisphenol-A polycarbonate (BPAPC) has an unusually high impact strength, there has been a great deal of interest in the elucidation of its dynamic properties. Nuclear magnetic resonance is one of a number of tools that have been used for this purpose.'