Ultrasonic absorption and shear viscosity measurements for solutions of polybutadiene and polybutadiene- block-polystyrene copolymers

Abstract

Ultrasonic measurements are reported on polybutadiene and polybutadiene- block-polystyrene copolymers in toluene. The ultrasonic absorption spectrum of polybutadiene can be described by the equation δα f 2 ∼f −n with the exponent n = 1 3 . The comparison of the measured dynamic shear viscosity with effective viscosity η eff shows that the ultrasonic absorption cannot simply be explained by contributions of the normal-mode relaxation. For the copolymers we can conclude from dynamic shear viscosity measurements that viscoelastic contributions have only a minor effect. The ultrasonic absorption of the diblock copolymers is higher than a pure superposition of the contributions from polystyrene and polybutadiene blocks. Therefore we assume an additional contribution from the relaxation of the volume viscosity (polymer-polymer interaction and/or polymer-solvent interaction) for polybutadiene and the copolymers.