Ultrasonic absorption in aqueous solutions of polyethylene glycol

Ultrasonic absorption spectra have been determined for aqueous solutions of polyethylene glycol, a linear molecule which assumes a random coil configuration, as a function of molecular weight (62-20,000) and frequency (1.5-163 MHz). The broad frequency range employed in this investigation revealed the presence of multiple relaxation processes. Similarities between the absorption dependence upon frequency and molecular weight of polyethylene glycol and dextran, another macromolecule which assumes a similar spatial configuration in solution, are pointed out. It is concluded that the observed ultrasonic absorption cannot be fully accounted for by shear viscoelasticity and that the presence of a bulk viscosity must be taken into account.