Simultaneous evaluation of ultrasound velocity, attenuation and density of polymer solutions observed by multi-echo ultrasound spectroscopy.

Ultrasound spectroscopy is a powerful tool to investigate the viscoelastic properties of materials. The longitudinal elastic moduli M' and M(″), or the adiabatic compressibility κ(S) can be evaluated from ultrasound velocity v and attenuation coefficient α via the relation M'=ρv(2) and M(″)=2ραv(3)/ω, where ρ is the density and ω is the angular frequency. So far, the density was independently measured by other equipments or its variation during the chemical reaction has been ignored in the previous literatures. Here we propose a multiple echo method to simultaneously evaluate α, v, ρ, from a single acquisition, enabling us to monitor the polymerization process of acrylamide, where the three parameters vary independently during the reaction. This allows us to analyze the time evolution of the acoustic parameters for polymeric or gelling systems with the better understanding.