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

Clear evidences of strong H-bond interactions, that occur in pure mole cular Ethylene Glycol (EG), in pure polymeric Poly-Ethylene Glycol (PE G), with mean molecular weight of 200 Da, (PEG200) and in their aqueou s solutions, are presented. The experimental result refers to IQENS an d compressibility measurements in the liquid phase. All the results ca n be interpreted if H-bond forces are taken into account. The diffusiv e motion of protons for the smallest molecules (EG) is well analyzed i n the framework of the random jump diffusion model both for pure and a queous solutions. This motion becomes strongly hindered, giving rise t o 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 compressibili ty evolution as a function of concentration, when the aqueous solution s are considered.