CONTRIBUTION OF HYDROGEN-BONDS TO APPARENT MOLECULAR MOBILITY IN SUPERCOOLED D-SORBITOL AND SOME POLYOLS

The dielectric relaxation in the supercooled D-sorbitol was measured and studied together with that in glycerol and isomeric butanediols. Apparent energies of activation incorporate the energies associated with the equilibrium rearrangements of hydrogen bonds. A macroscopic way to analyze the contribution from hydrogen bonds is proposed, which explains well the peculiar properties of the molecular mobilities in associated liquids. The contribution from hydrogen bonds plays a significant role in the pressure variation of the molecular mobility and alters considerably the apparent volume of activation. In the temperature variation of the molecular mobility, the contribution from hydrogen bonds is about 30%. The decomposition rates of hydrogen bonds with temperature and pressure are estimated.