Applications of densiometry, ultrasonic speed measurements, and ultralow shear viscosimetry to aqueous fluids

Precision measurements of density and sound velocity can be used to follow changes in fluids such as micellization or phase separation. Both technique s have been implemented in the oscillating tube density meters in different sample cells for several years. However, to get better results for the den sity of viscous samples, a correction for viscosity effects is necessary. T herefore, a viscosity-dependent signal must be measured, which can be achie ved by determining the damping of the oscillating tube. This is done routin ely in the latest generation of such density meters. We present a method to convert this measured signal into actual viscosity data up to about 300 mP a.s and show some applications of all three measured signals to different p roblems in the field of the study of complex fluids: Density and sound velo city can be used to establish water or any other pure fluid as a secondary standard for small angle scattering experiments. Viscosity shows temperatur e-dependent structural changes and the critical temperature of diblock copo lymers of the CiEj type. Finally, all three parameters-density, sound veloc ity, and viscosity-are used to establish a phase diagram of the PEO-PPO-PEO triblock copolymer P94 in aqueous solution.