Ultrasonic absorption and dynamic shear properties of the transition from dilute solution to the melt for polybutadiene

Abstract The frequency dependence of ultrasonic absorption ( α f 2 ∼ η eff ) and dynamic shear data ( G ′, G ″, η ′ s ) has been studied over a wide frequency range ( f = 10 4 – 10 9 Hz) in solutions (∅ = 0.03 – 0.8) of polybutadiene in 2-methyl butyl benzene and toluene as solvents and in the melt (∅ = 1). The ultrasonic spectra and the frequency dependence of the shear properties are both described in terms of subchain motions, entanglement effects and local motions. For increasing concentrations the crossover from dilute solution behaviour to the entanglement regime was detected. We have attempted to describe, in terms of the subchain concept, the influence of concentration on motions at frequencies above the entanglement region. The subchain motion in dilute solutions and between the entanglements have been described by combining the Muthukumar-Freed theory with relaxation times calculated by the Moiseev version of the Zimm theory taking into consideration the solvent quality. Deviations from the expected screening of the hydrodynamic interaction for the highest concentrations and the melt have been attempted in order to describe additional local high frequency relaxations connected to the dynamic glass transition. By comparing longitudinal ( η eff ) and shear ( η ′ s ) measurements it was possible to clarify the influence of subchain motions on shear and bulk properties.