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SOLUTION RHEOLOGY OF HYPERBRANCHED POLYESTERS AND THEIR BLENDS WITH LINEAR POLYMERS
Citation:
Nunez*, C M., B. Chiou, A. L. Andrady, AND S. A. Khan. SOLUTION RHEOLOGY OF HYPERBRANCHED POLYESTERS AND THEIR BLENDS WITH LINEAR POLYMERS. MACROMOLECULES. American Chemical Society, Washington, DC, 33(5):1720-26, (2000).
Description:
In this study, the rheological properties of different generations of hyperbranched polyesters in 1-methyl-2-pyrrolidinone solvent and their blends with poly(2-hydroxyethyl methacrylate) have ben investigated. All the hyperbranched polyester solutions exhibited Newtonian behavior, with steady shear viscosities independent of shear rate. This indicated the absence of physical entanglements in these systems. In addition, solution viscosity was only slightly affected by the different generations of the hyperbranched polymer. The polyesters have very small intrinsic viscosities and their hydrodynamic radius scales as Rh ~ M0.39, suggesting a less packed structure than dendrimers. All Generations also showed comparable apparent activation energies of flow over the temperature range studied. Replacing linear polymers with hyperbranched polymers caused large reductions in the blend viscosities. This behavior can be attributed to the decrease in both the number of physical entanglements between linear polymers and the blend's intrinsic viscosity upon addition of the hyperbranched polymer.