Viscosity dependence, polystyrene segmental

D. A. Waldow, M. D. Ediger, Y. Yamaguchi, Y. Matsushita, and I. Noda. Viscosity dependence of the local segmental diffusion of anthracene-labeled polystyrene in dilute solution. Macromolecules, 24 (1991), 3147-3153. 

Nevertheless, the difference between the temperature dependences of the terminal dispersion (or the viscosity) and the local segmental motion is significantly less for PIB than it is for PS. Dielectric-relaxation and PCS measurements (to be discussed later) have revealed that / (7 g) varies from polymer to polymer [34,164, 165,167,168], For example, polystyrene and polyisobutylene have a(.Tg) equal to 0.36 and 0.55, respectively [34,167,168]. This difference between the values of the stretching exponent j6a(7g) for polyisobutylene and polystyrene has been identified as the origin of their contrasting viscoelastic properties [169,170]. 

In contrast, all the hyperbranched polystyrenes used in the current study were fractionated by precipitation, i.e., according to the interaction parameter xM, where M is the overall molar mass of the chain and x is the Flory-Huggins parameter, a constant, independent on M for a polymer in a given solvent. Therefore, hyperbranched chains in each fraction used here have a similar molar mass. In comparison with our results, some of previous computer simulations [27, 28] suggested that the molar mass dependence of intrinsic viscosity of irregular hyperbranched chains deviates from Eq. 5.2 because the segment density distribution is different from those predicted by de Gennes and Hervet. We will come back to this point later. 

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