Experimental study of the dynamics of water and the phase behavior of the supercooled aqueous solutions of propylene glycol, glycerol, poly(ethylene glycol)s, and poly(vinylpyrrolidone).

The dielectric behavior of the supercooled aqueous solutions of propylene g ylcol, glycerol, poly(vinylpyrrolidone) (PVP), and poly(ethylene glycol)s o f different molecular weights has been examined at different concentrations in the frequency range of 10(6)-10(-3) Hz. Differential scanning calorimet ric measurements have also been carried out on the samples. The shape of th e relaxation spectra and the temperature dependence of the relaxation rates have been critically examined. In addition to the structural relaxation pr ocess that is responsible for the glass transition event at the calorimetri c T-g (the so-called alpha process in dielectric measurements), another rel axation of considerable magnitude is found to break away from the main rela xation on the water-rich side, which continues to the sub-T-g region. The s ub-T-g process dominates the dielectric measurements in higher PEGs, and th e alpha process is seen as a weak process. The measurements reveal that the aqueous solution at lower temperature is a single-phase system and should be treated as a statistically uniform liquid. The sub-T-g process is sugges ted to be due to the reorientational motion of the water molecules that are part of the matrix that has frozen at T-g. The measurements also suggest t he formation of 1:1 complexes in PG solutions.