Dynamical and structural properties of water/alcohol mixtures

Our recent studies related to the properties of alcohol/water mixtures, show the occurrence of some kind of molecular aggregation in the water rich region of composition beyond a threshold alcohol concentration x(2)*. The observed behaviour suggests that for x(2) < x(2)* the alcohol molecules are essentially dispersed and surrounded by ''water cages'' where the short range order and microdynamic of water molecules are changed with respect to those of pure water. Alcohol molecules are in mutual contact at higher concentration, only, when almost all water is involved in hydration shells of alcohol molecules. In addition, these studies show that the stabilisation of micellar structure and nucleic acids conformation in water/alcohol mixtures is closely linked to the properties and anomalous behaviour of the solvent systems. Accordingly, these results support the hypothesis that the dominant mechanism by which an alcohol affects these processes is through its effect on the structure of water. The main results of these investigations are reviewed and discussed in this paper.