Viscosity and photon correlation spectroscopy measurements in aqueous solutions of poly(ethylene glycol)

The present work reports the results of viscosity and Photon Correlation Spectroscopy (PCS) measurements performed on polymeric aqueous solutions. The viscosity data show that the transport properties of the H2O molecules in the presence of poly(ethylene glycol) differ greatly from those in the bulk. PCS data, on the other hand, allow us to evaluate the mutual diffusion coefficient and show that in the dilute region the system behaves as a polymer in a good solvent, whereas, at higher concentration indicates a scale behaviour, in agreement with the De Gennes scaling model for semi diluted solutions in a good solvent. An interpretative picture is proposed from these data: starting from pure polymers, and adding water molecules a certain number of these bond by H-bonding to the oxygen atoms of the oxirane groups, each oxygen atom being able to tie two water molecules so that the water-polymer interaction (hydration) plays a major role in the transport properties.