IQENS DIFFUSIVE BEHAVIOR AND HYDROGEN-BOND EFFECTS ON POLYMER-WATER SYSTEMS

Clear evidences of strong H-bond interactions, that occur in pure molecular Ethylene Glycol (EG), in pure polymeric Poly-Ethylene Glycol (PEG), with mean molecular weight of 200 Da, (PEG200) and in their aqueous solutions, are presented. The experimental result refers to IQENS and compressibility measurements in the liquid phase. All the results can be interpreted if H-bond forces are taken into account. The diffusive motion of protons for the smallest molecules (EG) is well analyzed in the framework of the random jump diffusion model both for pure and aqueous solutions. This motion becomes strongly hindered, giving rise to the spectral features that are typical of translational diffusion in confined region, in the case of aqueous solution of PEG200. Finally a not ideal mixing behaviour is detected by analyzing the compressibility evolution as a function of concentration, when the aqueous solutions are considered.