LCST demixing in poly(vinyl methyl ether)/water studied by means of a High Resolution Ultrasonic Resonator

A High Resolution Ultrasonic Resonator is applied to study demixing and remixing of poly(vinyl methyl ether) (PVME)/water solutions. The observed variation in ultrasonic properties (i.e., velocity and attenuation) is discussed in relation to microcalorimetry and Modulated Temperature DSC results. Throughout the phase separation process the ultrasonic velocity decreases due to the release of water molecules from the polymer hydration structure, while on the other hand the ultrasonic attenuation increases once aggregation sets in. The overall evolution of both ultrasonic signals is governed by the peculiar shape of the bimodal LCST demixing curve of PVME/water. The technique gives reliable results up to 20 weight% PVME.