Effect of Molecular Structure on Rheological Behavior of Nearly Monodisperse H-Shaped Polybutadienes.

Nearly monodisperse H-shaped Polybutadiene (PBD) with high 1,4 microstructure (∼90%) were synthesized by a novel synthesis strategy of living anionic polymerization. Linear viscoelastic properties over a broad frequency range of a linear PBD and an H-shaped PBD were studied by frequency sweep and creep/recovery experiments. The dynamic moduli of all samples were found to obey the time-temperature superposition. Primary attention was given to properties that depend on chain microstructure: the plateau modulus Q_N⁰, the steady state compliance J_s⁰, and the horizontal and vertical temperature shift factors for the frequency and modulus, a_T and b_T. The data are compared with the predictions of a hierarchical model developed by Larson. [ABSTRACT FROM AUTHOR]