SOUND-VELOCITY AND HYDRATION PHENOMENA IN AQUEOUS POLYMERIC SOLUTIONS

Sound velocity and density measurements were performed in polymeric aqueous solutions of poly(ethylene glycol) (PEG 600) and poly(ethylene glycol methyl ether) (PEGME 550) as a function of concentration and temperature. The experimental data unambiguously show that the presence of the polymer changes the water structure near the solute, building up a more compact arrangement in which up to two water molecules for each monomeric unity are allowed. Moreover we tested, at low concentration, a model to study the change induced in the polymer hydration by the addition of salt. No direct evidence of interaction between the hydration water of the polymer and salt is brought to light by the obtained results.